# '95 4 Cyl. Overcooling?



## LucidOne1 (Mar 26, 2009)

I've got a '95 4 cyl pickup that seems to be overcooling. Just want to make sure before I order a new thermostat that when they fail they fail open and not closed. 

The symptoms, when it's cold outside (<40 degrees) the engine wants to stall at idle. The temp gauge will hover around the cold mark and obviously gets worse if you run the heater.

I would check the codes but the check engine light just comes on for a second and then goes off once I accelerate. I'm not sure if they are stored on a '95 or not. 

If that sounds like the thermostat went out then great, if there is something else it sounds like then let me know. I'm not a huge fan of busting my knuckles open fixing the wrong part.


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## zanegrey (Dec 5, 2005)

fan clutch not t-stat...


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## LucidOne1 (Mar 26, 2009)

I'm assuming from your response they they don't fail open? The fan clutch failing would cause the fan to run all the time even when it isn't necessary?


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## jdg (Aug 27, 2009)

LucidOne1 said:


> Just want to make sure before I order a new thermostat that when they fail they fail open and not closed.


As far as I know, the old school t-stats failed closed, the newer ones fail open...but I don't know what year the 'break' was...



> The symptoms, when it's cold outside (<40 degrees) the engine wants to stall at idle. The temp gauge will hover around the cold mark and obviously gets worse if you run the heater.


That tells me that you might also have a problem with your idle air control valve/solenoid/whatever-your-engine-has-on-it. Or maybe even your coolant temp sensor...



> I would check the codes but the check engine light just comes on for a second and then goes off once I accelerate. I'm not sure if they are stored on a '95 or not.


Is the check engine light coming on because the engine is trying to die or because maybe the computer is thinking something is broke?
If it's because the computer is maybe thinking something is broke, and you have access to a decent code reader, you might be able to read a 'pending code' which isn't a real code, but it's a code the computer is basically thinking about setting.



> If that sounds like the thermostat went out then great, if there is something else it sounds like then let me know.


Another possible problem with 'overcooling' is just a bad antifreeze/water mix. It's a bit of a stretch, but, ya never know...



> I'm not a huge fan of busting my knuckles open fixing the wrong part.


Aw...come on!!! That's half the fun! Especially when you get to say that you did it yourself for $10 vs paying a shop $250.


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## zanegrey (Dec 5, 2005)

fan clutch ..nothing else...


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## LucidOne1 (Mar 26, 2009)

Ok going with the fan clutch thing I decided to look it up. The Haynes manual says that basically you have to replace the water pump in order to replace the fan clutch. But, for instructions on how to replace the fan clutch it sends you to section 8 of the manual aka the section on how to replace the drive clutch. Nice work Haynes, can I get my $20 back? 

So, I go to the FSM and it doesn't even list a fan clutch in the cooling system. Like it doesn't exist. Unless all of a sudden the water pump has nothing to do with cooling the engine and I'm looking in the wrong section. Possible.

Can someone explain?


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## LucidOne1 (Mar 26, 2009)

jdgrotte said:


> Is the check engine light coming on because the engine is trying to die or because maybe the computer is thinking something is broke?
> If it's because the computer is maybe thinking something is broke, and you have access to a decent code reader, you might be able to read a 'pending code' which isn't a real code, but it's a code the computer is basically thinking about setting.



remember, it's a '95. I have an awesome code reader. It's called: pullingtheseatoutandlookingatgreenandredlights. Catchy name huh?


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## zanegrey (Dec 5, 2005)

the fan clutch is attached to the water pump and can be removed w/o disturbing the 
water pump...


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## LucidOne1 (Mar 26, 2009)

The fan spins free. Meaning that it can't possibly be the fan clutch over cooling the engine. Otherwise, it would be locked and constantly spinning the fan. I'll pull over and check it the next time it happens to see if it's intermittent. Too bad, kinda, here in az it's not often cold enough to cause the symptoms.


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## jdg (Aug 27, 2009)

zanegrey said:


> fan clutch ..nothing else...


NOTHING else?

Does the heater blow hot air...at all...ever?


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## LucidOne1 (Mar 26, 2009)

Another thing I'm checking on. I saw that as a symptom of the fan clutch going out. I remember it being hot before I noticed my temp gauge below the cold mark and the idle started jumping at stop lights. I guess logically I need to know if running too cold can cause your idle to jump between 500 and 1200 rpms. Or, is it the fan clutch sticking and loading and unloading the engine.


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## jdg (Aug 27, 2009)

LucidOne1 said:


> Another thing I'm checking on. I saw that as a symptom of the fan clutch going out. I remember it being hot before I noticed my temp gauge below the cold mark and the idle started jumping at stop lights. I guess logically I need to know if running too cold can cause your idle to jump between 500 and 1200 rpms. Or, is it the fan clutch sticking and loading and unloading the engine.


Fan clutch - jeeze, I'd really lean away from that theory. I'd think a guy would be able to actually HEAR a fan clutch kicking in and out, which I wouldn't think would actually be physically possible without the engine heating up/cooling down along with it.
And if you're idle is jumping around from 500 to 1200, you've got other problems, not just some cooling fan thing going on.
Check that temp sensor, check the idle air control valve, 1st off, check for vacuum leaks...everywhere!


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## LucidOne1 (Mar 26, 2009)

Seems like any one of those things would throw a code. I'd yank the seat out but I didn't get a response when I asked if the ECM stored codes if the check engine light just flashed for a second. I guess I'll pull the seat and check it out, probably needs to be vacuumed under there anyway. Oh, and hook a voltage tester to everything temp related.


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## jdg (Aug 27, 2009)

LucidOne1 said:


> Seems like any one of those things would throw a code. I'd yank the seat out but I didn't get a response when I asked if the ECM stored codes if the check engine light just flashed for a second. I guess I'll pull the seat and check it out, probably needs to be vacuumed under there anyway. Oh, and hook a voltage tester to everything temp related.


As I said in post #4, there could be a 'pending' code, which won't trip the light and keep it on, but it'll still be stored, and you won't be able to pull the code with the 'turn the screw' method, has to be done with a code reader that will actually read 'pending' codes.


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## LucidOne1 (Mar 26, 2009)

Auto Zone will loan me a code reader, but where do you hook one up?


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## zanegrey (Dec 5, 2005)

now i am old so don't go by me but u r the reader...


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## LucidOne1 (Mar 26, 2009)

Zane, I'll order the part today if you can tell me why you think it's the fan clutch. I generally don't just throw $60 out the window because someone says to. There has to be a reason why you think it's that part.


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## zanegrey (Dec 5, 2005)

read the sticky that tells u how to read the codes..

then check the codes..

then tell me what the codes is...


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## LucidOne1 (Mar 26, 2009)

will the code store if the check engine light doesn't stay on? It seriously just flashes for a second at a time.


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## jdg (Aug 27, 2009)

LucidOne1 said:


> will the code store if the check engine light doesn't stay on? It seriously just flashes for a second at a time.


Don't know if you're reading every post or what the deal is...but...

Your vehicle, apparently as you've stated, is a 1995 model. Most likely (especially since it's an 'import') your 1995 vehicle is OBDII compliant, which means, according to the OBD specifications, the OBD connector will be located within something like 2 feet of the drivers knees (don't know if that's the right distance, or if it's the right reference, but I'm sure it's close).

And if you've been reading the posts, you'd realize that I stated that PENDING codes won't be read out by a cheapo code reader like you'll get off eBay and maybe not even by a standard code reader from Autozone. BUT...PENDING codes can be read by a capable OBD code reader.

And is that check engine light flashing because your engine is wanting to stall? Are there other lights that flash at the same time?
Or is it actually flashing on command from the ECU? That's the kicker.
If it's flashing along with other lights at the same time, then it's probably flashing because your engine is that close to a stall, it may as well be off (i.e. alternator light, brake light, oil light, etc. all flash at the same time)

So...which is it?

I think you're wasting $60 if you go out and buy a fan clutch, especially without decent troubleshooting.
If the fan clutch is locked up, the engine overcools...or will it? I mean, isn't that what the thermostat is for? Have you pulled it out and checked it? And there's practically zero chance of any overheating damage to your engine.
If the fan clutch spins freely 100% of the time, the engine might overheat at a stop-light....not your problem...
So, how's that $60 looking?


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## zanegrey (Dec 5, 2005)

if the fan clutch is to tight it can over cool..

if it is too loose it can over cool..as it can move from the wind at speed..

if u seriously do not think it is the fan clutch check the t-stat b4 u buy n e thing..


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## LucidOne1 (Mar 26, 2009)

OK, I'll check the thermostat and see if my mechanic can pull a pending code for me. It is just the check engine light that flashes but you're correct in saying that it only flashes when it is very close to a stall. Worth a shot and he'll do it for free. I have yanked the dash apart and never seen a OBDII hook-up, but then again, someone put a cheap alarm under there and it looks like a spaghetti bowl of wires because of it.

Sorry for so little action on my part, but I work two jobs and need to fix it in one shot if possible. Time spent working on it is lost money.


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## jdg (Aug 27, 2009)

LucidOne1 said:


> OK, I'll check the thermostat


One easy way to check if the thermostat is stuck open, take off the radiator cap, start the engine from cold, watch the water.
Water moves, it's probably open.
Wait for a couple of minutes and give the upper radiator hose a squeeze. You should be able to feel the water flowing.

Never did answer if the heater blows hot air or not...after the engine has been running awhile.



> and see if my mechanic can pull a pending code for me. It is just the check engine light that flashes but you're correct in saying that it only flashes when it is very close to a stall.


Wouldn't waste your time. It's getting tripped by the near-stall condition.



> I have yanked the dash apart and never seen a OBDII hook-up


Have you googled OBD 2 connector and looked at a picture of one?
After all, seems to me that you've got an internet connection.


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## LucidOne1 (Mar 26, 2009)

Ok, it's fairly cold out this morning so I'll try what you said about testing the t-stat before I go to work. 

I tested the heater and I suppose I'm on the fence. It's warm but not hot. Knowing the PO personally he used to let it sit on for 30 minutes on cold mornings before he got into it. So, I'm not sure if "hot" ever happened, or if warm is the best the truck ever had.


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## LucidOne1 (Mar 26, 2009)

Also, according to obdii.com, I don't got one.


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## LucidOne1 (Mar 26, 2009)

Thermostat appears to be functioning. No water running on start-up, but also no water running, that I can feel, after my 3 mile drive to work. I didn't pull the radiator cap when I got here, for obvious reasons, but I didn't feel water running through the hose.


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## LucidOne1 (Mar 26, 2009)

Checked the thermostat, no water moving when I started it. After my 3 mile drive to work it still didn't feel like it was moving though. Didn't pull the cap, for obvious reasons, but I couldn't feel anything in the hose. I'll do it again on my way home when it's a little warmer to be sure. 

The water/coolant was pretty brown also, don't know if that means anything except it needs to be flushed, but I thought I would mention it.

sorry for the double post, previous one wasn't showing up.


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## zanegrey (Dec 5, 2005)

update please...


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## 92 GSR-4 (Oct 10, 2009)

Geez this is pretty amazing. I've never heard of an engine overcooling. I'm excited to see what the problem turns out to be.


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## brookwood61 (Aug 18, 2005)

With the coolant being brown, there is a good chance the thermostat is shot, or you have a blockage, creating an air pocket. If you can get it back flushed, it would help.
Good Luck


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## zanegrey (Dec 5, 2005)

maybe the sensor ?


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## cjserio (Mar 18, 2008)

I had this problem on my 1994. I got 0 heat out of the truck and the temperature gauge never moved off of the bottom of the scale. I got a new thermostat ($17) and a new fan clutch ($60) and installed them. Now the temperature gauge goes up half way, I get nice warm heat in the winter and the truck seems happy.

I don't think i needed the thermostat at all, i tested it and it worked fine but it was fairly easy to change it so i did. The fan clutch on the other hand was very dirty and corroded on mine and i couldn't rotate the little center of it until I gripped it with pliers and sprayed it with PB Blaster so it was definitely time for a new one.

No codes ever showed up.

So you need to answer the questions:
1) What does your temperature gauge read?
2) Do you get nice warm heat out when the engine is running properly.

If you're not getting heat and the gauge reads low, it's overcooling and you probably need a fan clutch or thermostat. If you get good heat, maybe it's just the sensor.


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## LucidOne1 (Mar 26, 2009)

UPDATE... Flushed the coolant, possibly will again to make sure all that rust is out. Pretty much I have a bucket with what appears to be mud but smells like sweet propylene glycol. 

We've been unseasonably warm so I haven't had a chance for the symptoms to return since our 2 day cold snap when I started this thread. 

According to my mechanic, and all of you, I'll need to check the temp sensor to make sure that it isn't giving a -40 degree reading to the ECM, but I've been spending my saturdays catching the truck up to its 60,000 mile service. Repacking wheel bearings, egr valve, inspecting everything, etc.

I'll report back as soon as winter gets to Arizona and I either do or don't get symptoms.


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## zanegrey (Dec 5, 2005)

maybe just some cardboard in front of the rad...


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## LucidOne1 (Mar 26, 2009)

I said Arizona, not Kentucky


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## zanegrey (Dec 5, 2005)

maybe some of the old pink uniforms from the sheriffs out door camps...


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## LucidOne1 (Mar 26, 2009)

Wrong county, but touche.


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## smikster (Aug 12, 2008)

i would flush that thing till its shiny lol. I've owned 2 and ran 3 hb all everyone had to have the cardboard when it got cold...ya know...I've never had one over heat...even in 4lo crawling across god knows what in 100+ heat....also didn't have ac...urg


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