# Engine temp stays cold



## Azazel (May 3, 2009)

Well another problem for me. 1995 hb 4x4 2.4. My temp on my truck stays cold and only sometimes rises above the cold maybe to slightly a quarter of a tank mark. I have replaced 

new coolant switch/sensor
new radiator
new water pump
new thermostat 
flush heater core

I have grounded the wire for temp and my needle goes to high. Have bleed air out of the system with the screw on intake, Just don't know what else to do. Now I live in smoky mtns driving on highways the temp just comes up to the end of the cold mark. When going up mtn roads the temp will rise to the quarter tank mark or just tad under it. but soon as back on highway it drops back down. Heat works but just enough to break the chill but when temp gets to the quarter mark it will run you out. Does anyone have some other ideals?


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## rogoman (Dec 16, 2004)

Did you install a new Nissan OEM thermostat rather then an aftermarket thermostat? Many aftermarket types open too soon and fail to properly regulate the temperature.


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## smj999smj (Jan 1, 2006)

My thoughts, exactly! Aftermarket thermostats, in my experience, always seem to cause slightly cooler gauge readings than the OEM thermostat. It's also possible that the new thermostat is faulty. I would get a genuine Nissan thermostat.


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## Azazel (May 3, 2009)

It's a stat from autozone. But the one I took out was same thing I bought few years ago. It has ran fine for years. But thats what I was thinking also that it opens to soon. Just don't understand why stopped working unless it was the new water pump and radiator. When looking in the radiator it looks like a river flowing circulating good.


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## smj999smj (Jan 1, 2006)

A radiator nor water pump will cause an engine to run too cold; only a bad thermostat will do that.


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## jp2code (Jun 2, 2011)

Shifting focus of this issue:

An old O2 sensor will send incorrect readings to the ECU, causing the engine to run Too Rich or Too Lean.

If you are running Too Rich, your engine will run cooler.

Nissan recommends O2 sensor get replaced every 60k miles. How many miles are on yours?


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## smj999smj (Jan 1, 2006)

An oxygen sensor with a shift that would cause the ECM to increase the fuel injector duration to make it run richer, might cause slightly cooler combustion temperatures, but not to the point where the engine coolant would be adversely affected to the point where the coolant would run that cold. As far as the 60,000 mile oxygen sensor interval, there are very few vehicles on the road that need the oxygen sensor replaced at that time. I remember in the early 80's, Nissan had a sensor light that needed to be reset every 30,000 miles to remind that the oxygen sensor needed to be checked. There are plenty of vehicles on the road with well over 100,000 miles on their oxygen sensors and they work perfectly fine; I had over 200,000 on my 97 Hardbody's before I sold it. I'm not saying it's not worth checking the operation, but I just don't see it causing the OP's coolant problem.


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## ahardb0dy (Nov 9, 2003)

possibly the wire to the sensor is bad, when you ground the wire for the sensor and the gauge went fully up, shows the wire you grounded it with works, but the actual wire to the sensor may be bad, I would check the temp with a infrared thermometer to see if it is reading what the gauge is showing. 

Since the heat works good when the gauge goes near the 1/4 mark, than possibly the engine is running/cooling properly but the gauge is reading low.


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## smj999smj (Jan 1, 2006)

_"when you ground the wire for the sensor and the gauge went fully up, shows the wire you grounded it with works, but the actual wire to the sensor may be bad"_

That statement contradicts itself. There is only one wire in the circuit between the gauge and the temperature sensor. The sensor is a variable resistor to ground. When you unplug the wire at the sensor and ground it, you are providing full ground for the circuit, which should cause the gauge to go to full hot. This test lets you know the wire circuit is good. If the wire was broken or "open," the gauge would not read at all. If the wire was shorted somewhere, the gauge would read full hot all of the time. If there was excessive resistance, like corrosion, in the wire, the gauge would not go to full hot, it would read something less, dependent on how much resistance is in the wire.


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## ahardb0dy (Nov 9, 2003)

I stand corrected, thanks


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## jp2code (Jun 2, 2011)

A cold running engine could also have a leaking fuel injector.


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## Azazel (May 3, 2009)

I bought oem thermostat should be in today by time I get home. So going try get it put in today. As far as o2 sensor it has been replaced but probably have over 60k on it by now. But wouldn't o2 cause a code? I'm going to check the coolant temp after I drive it for a while to know a number on it. How hot should coolant be? My mileage on gas is about the same most the times but few times it is a lot worse. I keep up with it a lot. I get on avg about 150 miles on 9 gallons. Which puts me at quarter tank and 16mpg. Never run it to E. But few times sense this problem I have gotten as low as 12.5mpg driving same 150 miles but taking 12 gallons to fill up. I reset trip counter every fill up cause my cluster had stopped working for good while before I replaced it.


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## Azazel (May 3, 2009)

This is over hour of driving.











This is after going up a mtn road. This was a chilly morning, warmer days mtn road will bring it up little higher


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## jp2code (Jun 2, 2011)

If you had a "lazy" O2 sensor, there would not be a code but the ECM would still tweak the amount of fuel it is adding to get the mixture back where it thought it should be.










Since yours is not that old, I'd look at the connector for that O2 sensor. The wire should route around the transmission and up into the engine compartment, just behind the battery. Pull the connector apart, make sure all of the wires look good, no corrosion, etc. then plug it back in.

The CEL should only turn ON under a few conditions:










If that does not make the Check Engine Light (CEL) go out after a few miles, I'd suggest Ohming the injectors.










You could also check the resistance across the thermostat temperature sensor.


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## SPEEDO (Jun 9, 2003)

stupid question... have you checked the fan clutch?? is it locked up?


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## Azazel (May 3, 2009)

So I changed out thermostat with oem one and it didn't make a difference. And I did check the clutch fan and it is fine. I didn't get to check coolant temp yet. And for my check engine light that is code 32 on egr. Another problem I have been working on eliminating. But will test o2 and check injector here in few days going have some long days at work rest of this week.


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## jp2code (Jun 2, 2011)

Checking the EGR valve isn't too hard.

Check that it holds some vacuum:










Then, check that the diaphragm moves in and out freely:










Mine was fine, but cleaning it up still made a noticeable difference in my engine idle.

You can clean the EGR, but it takes a really big wrench to get it off - metric 26, or something like that.

If you can get it off, squirt a bunch of Carb Cleaner into it, and work the plunger around.

Usually it gets clogged up over the years with carbon deposits, so a little Carb Cleaner will work wonders on it.

Of course, I also just like this picture:


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## Azazel (May 3, 2009)

Thanks for these pics few of these I have not tried. I have taken it off and cleaned it up and the bpt early this year when I put new head on my truck. I also changed all my vacuum hoses out. It's just weird cause the light comes on for while then goes off. Some weeks if can go days and not see check engine light come on then it may come on and stay on for few days or just come on hour or so then go off. But it's always a code 32.


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## jp2code (Jun 2, 2011)

For Code 32, there are 3 pages of diagnostics in the 1994 Service Manual, pages EF & EC-239 to page EF & EC-241.

It shows where to check for vacuum leaks, how to inspect the EGR valve, EGRC-BPT valve and EGR temperature sensor, EGRC-solenoid valve, what pins to check on the ECU, etc.

I can't post a link, but I can post the pic of where to find it:










Look for the EC file.

This forum will not let you post the word *nico* and *club* as one word.


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## rogoman (Dec 16, 2004)

Azazel said:


> So I changed out thermostat with oem one and it didn't make a difference. And I did check the clutch fan and it is fine. I didn't get to check coolant temp yet. And for my check engine light that is code 32 on egr. Another problem I have been working on eliminating. But will test o2 and check injector here in few days going have some long days at work rest of this week.


After the engine is fully warmed up, check the bottom radiator hose to see if it's hot; also turn on the heater inside the truck to see if it blows out hot air. If so, then the temperature gauge or connections or the sending sensor may be bad. Also make sure the coolant system is fully purged of air.


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## Analognerd (Oct 5, 2014)

*Is this a problem?*



Azazel said:


> So I changed out thermostat with oem one and it didn't make a difference. And I did check the clutch fan and it is fine. I didn't get to check coolant temp yet. And for my check engine light that is code 32 on egr. Another problem I have been working on eliminating. But will test o2 and check injector here in few days going have some long days at work rest of this week.


 Hi, I saw your pic of your temp gage after 1hr running. Is this a problem? My old Tempo ran at that temp for years. And I had other cars that did also. My dad use to say "Heat kills motors" So I was happy to see it was not close too running hot. Ya, it wasn't the warmest car to ride in.
Once it is up to temperature. Have you tried to put an thermometer into your baby's radiator mouth to see what the temperature is??? Maybe its OK.


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## jp2code (Jun 2, 2011)

Analognerd said:


> Hi, I saw your pic of your temp gage after 1hr running. Is this a problem? My old Tempo ran at that temp for years. And I had other cars that did also. My dad use to say "Heat kills motors" So I was happy to see it was not close too running hot. Ya, it wasn't the warmest car to ride in.
> Once it is up to temperature. Have you tried to put an thermometer into your baby's radiator mouth to see what the temperature is??? Maybe its OK.


Most radiators are under high pressure at an engine's operating temperature, so please don't try opening the radiator cap once the engine is up to temperature.

Most newer vehicles are designed to operate within a certain temperature range. If they are not running at that temperature, the ECM will feed fuel to the engine like it is still cold.

If your engine does not get hot enough, it will not have a way to burn the moisture out of the oil. Oil is used in tight clearance areas like the crankshaft bearings, and it can instantly go from 100°F to 300°F or more. If moisture is suspended in the oil, you will get micro-explosions as the moisture transitions into steam, which will pit your bearings and cause premature bearing failure.


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## tomit (Jul 2, 2004)

If there is enough heat in the cabin during winter and no water (via condensation) in the oil and gas mileage is normal, I would not worry about it.


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## smj999smj (Jan 1, 2006)

I think the main issue is whether the coolant is actually running colder than it should or is the gauge reading incorrectly. Use a thermometer to measure the heater output at the vent with the engine fully warmed up and heater set to maximum "hot" setting. The heat vent at the floor should be putting out air at a temperature of around 130-140 degrees F. Run the engine at speed with the cap off until you see the coolant cycling; thermometer should read about 170+ degrees F. If the temperatures are in that range, the sender is new and the circuit tested good, it would seem that the accuracy of the gauge is off. You may want to pull the cluster and double-check the resistance of the wire between the gauge and the sender with an ohmmeter.
If the thermometer readings are significantly colder than those temps, it's a coolant system issue, and not the gauge/sender/circuit.


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## wornwrench (Oct 25, 2014)

Yes, to the main issue. the man said he sees the coolant flowing in the radiator with
the cap off. that's not a thermostat controlled flow! It's a bypass thermostat which
has a disc on the engine side to stop bypass during thermostat regulation of temp.
the thermostat is NOT closing. As for the gauge/sender issue, the gauge is calibrated
for a certain temperature reading correlated to the recommended thermostat temp..
they go sour sometimes and will read colder or hotter. the important factor is the
engine tempertaure which is simply the thermostat, excepting engine failures.
I use a temp. gun to check hose/coolant temps., however simply done, the upper
radiator hose should become min. 160 degrees during thermostat opening. that's
the easy way to tell. best to check while idling, cap off is fine. working system will
pulse coolant up/down not "river flow". keep it simple. good luck.


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## Azazel (May 3, 2009)

We'll I bleed the radiator system again still had some air coming out did it for an hour or longer. So after I felt that I had all the air out I rev the motor up to about 2k held for a min or so, this is with my funnel still in radiator full of coolant. So when came back around I notice very small bubble and coolant started looking frothy or like beer suds. So I was thinking bad head gasket getting combustion gas in coolant. Went and got block tester. Got home pop hood open cap and it's has an inch or so of beer suds. I tested it with block test and it was negative. So I got me a temp gun and these are my temps.

Radiator coolant from the fill hole. Low 98 highest 115
Top hose. 115 
Engine head front 134 back 218
Therm housing 115
Exhaust manifold 325 by head by o2 sensor 502
Heat on inside truck low 90s longer I held gun there maxed out at 120.3

So open to any other things to try.


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## Azazel (May 3, 2009)

Just little update on this. I ended up blocking 2 sides of my radiator with cardboard only leaving the center exposed. My temp now rises up to slightly under the quarter tank mark on cold days and on warmer days a little pass quarter mark while driving to half tank make when sitting and idling. But no over heating.


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## jp2code (Jun 2, 2011)

I hope your temperature gauge is correct.


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## Analognerd (Oct 5, 2014)

*Suds?*



Azazel said:


> We'll I bleed the radiator system again still had some air coming out did it for an hour or longer. So after I felt that I had all the air out I rev the motor up to about 2k held for a min or so, this is with my funnel still in radiator full of coolant. So when came back around I notice very small bubble and coolant started looking frothy or like beer suds. So I was thinking bad head gasket getting combustion gas in coolant. Went and got block tester. Got home pop hood open cap and it's has an inch or so of beer suds. I tested it with block test and it was negative. So I got me a temp gun and these are my temps.
> 
> Radiator coolant from the fill hole. Low 98 highest 115
> Top hose. 115
> ...


Suds?
When I heard your temp was low I first thought your thermostat was in the wrong way and all-ways open from the force. Then I thought some one put a rebuilt radiator in your car and it was too good. Now suds makes me think some one put windshield washer fluid in buy mistake. It does sound like air too. But suds?
Is this with new fluid? You can't pump suds. Is your electric fan shutting off? Suds, like soap suds? I would change the fluid / flush with water then refill and if the suds come back I would think head gasket also.


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## smj999smj (Jan 1, 2006)

If it's a Hardbody, it doesn't have an electric fan unless someone installed an aftermarket fan. Also, there's no way to make a radiator "too good." Regardless of how cool the coolant gets in the radiator, the coolant in the block will still need to get to the temperature setting of the thermostat before the thermostat opens to circulate the coolant. The coolant in the heater core should be the same temperature that is in the block. An improperly installed thermostat crossed my mind; it still sounds like a thermostat issue. Even washer fluid shouldn't have that much of an affect on the temperature if it were installed in place of coolant, as it is composed of distilled water and isopropanol. A head gasket failure could create air pockets, but the combustion gases should help to raise the temperature of the coolant and will usually cause overheating.


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## Analognerd (Oct 5, 2014)

*Too Good*



smj999smj said:


> If it's a Hardbody, it doesn't have an electric fan unless someone installed an aftermarket fan. Also, there's no way to make a radiator "too good." Regardless of how cool the coolant gets in the radiator, the coolant in the block will still need to get to the temperature setting of the thermostat before the thermostat opens to circulate the coolant. The coolant in the heater core should be the same temperature that is in the block. An improperly installed thermostat crossed my mind; it still sounds like a thermostat issue. Even washer fluid shouldn't have that much of an affect on the temperature if it were installed in place of coolant, as it is composed of distilled water and isopropanol. A head gasket failure could create air pockets, but the combustion gases should help to raise the temperature of the coolant and will usually cause overheating.


 Yes, Your right. That would need to be one kick but radiator and it wouldn't fit in the car. Now there's one that would need to be closed off...


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## Analognerd (Oct 5, 2014)

OK, Here's what I would do if I was you. I would buy a new thermostat and I would put it in. The coil side goes down with the point-like side up facing the radiator. The thermostat opens to the temp of the thermostat 160 - 190. And it opens against the flow of the fluid. (and that is from the bottom to the top). If the thermostat is placed upside-down, it will open just from the force of the flow. Some housings are made so it can't be put in the wrong way but I've seen some where some one could make that mistake.
I would check the water pump pulley and see that it is turning the shaft and there's no broken key or what ever drives it. I would check to see that its turning the right way. There's no telling what mistakes people can do be-for you.
I trusted you knew not to open the radiator with out some hand protection when hot. But I'm not sure about these other things. At first it sounds like a stuck (open) thermostat. Make sure you have the right kind so it seats right. Use a new gasket too, it should come with one.
After that, I would bring it to a shop. BUT like I said. I have had two cars that showed low temp. on the gage and ran warm. One had a very small 900cc? motor and a BIG radiator. The other was a freak too.
But that foaming means something is up. That's why I brought up the water pump. I did have a car that dropped a water pump belt and I drove it home that way OK. It was winter and I didn't care about the car. I fix it when I got home but it didn't kill it. It was winter and maybe it got air cooled. That was a tiny engine car also.
I hope you let me know when you fine it. I'm sure wondering my self...


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## smj999smj (Jan 1, 2006)

The water pump pulley can't slip on the shaft; it fits over four studs that are screwed into the water pump flange, sandwiched between the pump flange and the fan clutch flange, and held on with four nuts. It used older style drive belts, not a serpentine belt, so rotation should not be an issue. He already stated he replaced the thermostat with a genuine Nissan part without any change. Whether or not it was installed correctly, I cannot say; I'm pretty sure the thermostat won't install backwards on this engine, as it hits the housing when improperly installed. It's pretty rare that a new, genuine Nissan thermostat fails, but I guess anything's possible! I'm out of ideas!


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## Analognerd (Oct 5, 2014)

*Dear Out of Idears*



smj999smj said:


> The water pump pulley can't slip on the shaft; it fits over four studs that are screwed into the water pump flange, sandwiched between the pump flange and the fan clutch flange, and held on with four nuts. It used older style drive belts, not a serpentine belt, so rotation should not be an issue. He already stated he replaced the thermostat with a genuine Nissan part without any change. Whether or not it was installed correctly, I cannot say; I'm pretty sure the thermostat won't install backwards on this engine, as it hits the housing when improperly installed. It's pretty rare that a new, genuine Nissan thermostat fails, but I guess anything's possible! I'm out of ideas!


Crap! My cat just sat on the key board and deleted every thing. I will try again... I was wondering if by chance he put a gasket on and the thermostat over the gasket so the thermostat could flout around free like it was open?
I have had cars be-for than ran very low warm but no fome...he spoke off. I'm not sure a low-med temp would cause a higher choke setting. It seems to me that it would not idle normal if it did.
One thing to me is that if he has flow that he doesn't need to worry about over heating and he has time to fine the problem. I'm guessing the car really runs cool because he doesn't have a problem with the radiator cap spiting out.
My first thought was that if he has a car that runs that cool that he should feel lucky and that the car may last a long time because of it. I'm going to see what kind of low temperature thermostat I can fine that will fit my Sentra. I can tough out the winters with low heat for the sake of the motor.
Its just what I believe. I could be wrong. But I would feel safer on the low side of what they call normal, far from over heating.


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## Analognerd (Oct 5, 2014)

*Smokeys? Cool...*



Azazel said:


> Well another problem for me. 1995 hb 4x4 2.4. My temp on my truck stays cold and only sometimes rises above the cold maybe to slightly a quarter of a tank mark. I have replaced
> 
> new coolant switch/sensor
> new radiator
> ...


I just found your Org. Post. I once came through the Smokey's on some back roads from the NC? I was driving a old 72 Simca (French) Small 4 banger with electric fan. When it got too hot, I pulled over and let the fan cool it down. If the car died I would have sold it for a buck and took a bus home to NH. $150 the car lasted many years and was still running (tho burn oil) when I gave it away. Best ride ever through the Smokey's. Love the people through there to Kentucky. Even thought about living there. Back then cost were great!
Some one may have done something to the car to keep it cool running for those hills. If Its used. Glad I found the org. post... Shannon.


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## smj999smj (Jan 1, 2006)

The KA engine uses RTV sealant as the thermostat gasket, so I couldn't see the thermostat sitting on top of it. Aftermarket paper gaskets exists, but not installing it properly would lead to a coolant leak at the housing. 
You don't want a computer controlled engine to run too cool, or it will not enter into closed loop when the ECM uses input from the oxygen sensor(s) and other sensors to efficiently run the engine. Also, if the engine runs too cool, it will not burn off the condensation that can develop in the crankcase. It's best to stick to the operating temperature as designated by the manufacturer.


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## Analognerd (Oct 5, 2014)

*Timeing?*



smj999smj said:


> The KA engine uses RTV sealant as the thermostat gasket, so I couldn't see the thermostat sitting on top of it. Aftermarket paper gaskets exists, but not installing it properly would lead to a coolant leak at the housing.
> You don't want a computer controlled engine to run too cool, or it will not enter into closed loop when the ECM uses input from the oxygen sensor(s) and other sensors to efficiently run the engine. Also, if the engine runs too cool, it will not burn off the condensation that can develop in the crankcase. It's best to stick to the operating temperature as designated by the manufacturer.


Ya, I'm fine with what you say. If the coolant flows there shouldn't be an air pocket. I would sill go over that thermostat and try a other brand of one. Some one posted how the resistance changes on the censer and how to check that. But your saying... The darn thing runs cold. Now I know this is a long, long shot but. Some times in my past I rush and set the timing by ear by how the car ran. I notice that if the timing was too low that the engine would run on the hot side. So: Could too high timing make it run cool???? I don't think so with a working thermostat but I had to throw that out there.
I still believe that a too good of a radiator could make a car run cool. Does yours look rebuilt with a wider core (not longer- thicker) than normal?
I bet your oil looks fine...
Also I have to wonder about shorts in the temp coil. SO : no heat or very low heat when its turn on? My car showed a low temp on its gage but it blew like it was wormed up enough.
I hate to see you pull the head to get the same results and I'm not going to suggest it. I'm Just dispensing theory's 
Did this car come this way? Are you sure its not normal for it? Have you tried a new temp gage? You can't fine a cheap $1 water thermometer to put where the coolant come out by the radiator cap?
You have all ready proved that the radiator works TOO good. A less of a radiator and you get normal reading.
Why not test drive a car like yours and see what that does and see if the radiator is the same as yours. OK, Bla, Bla, Bla, remember that stupid timing thought I had. May-be some one turn it way up for more power. I think some balance is off. But to me its off in your favor.
Isn't that the dearness thing?
I lived with mine. Shannon.


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## Analognerd (Oct 5, 2014)

I had posted that I found the advance of timing cool the temp but I read that advance timing will heat the motor so maybe I had that back wards. Still just timing alone I wouldn't think could do that so much but it will change the operation temp.
Hot plugs will also. So out of the box thinking I'd like to throw in the thought of low timing or cold plugs. Now I know that this is a stretch, but I'm thinking we need to cover every-thing no mater how silly.
Maybe what I read was wrong and I was right. Just know it maters.


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## Shut-Trip (Oct 18, 2012)

My '97 p/up started showing the low Temp gauge problem a couple weeks ago.

I assume / presume, that the engine is staying cool.
is that a valid presumption?
and could that be leading to other problems ?


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