# Overheating/losing power on freeway



## pepperjack13 (Jun 20, 2010)

I have had this problem like three times recently and in very special circumstances. 
First time, after a border patrol check point on the freeway I tried to reach the speed limit (75mph) from a stop and right around 70mph all of a sudden the car loses power and starts to overheat. I can hear the engine revving as I tried to give it more gas but the speed is going down and the temp needle is going up (there is no weird noise or vibration by the way). I pulled over and nothing seems wrong, nothing is leaking, no smoke, coolant level is ok, no nothing. I wait for it to cool down, keep driving at 75mph and everything seems ok except that the coolant temperature is around 205f (normally 185f). After that incident I changed the coolant, which is something I haven't done since I bought the car 5 yrs ago!. It doesn't help a bit.

The last two times that the same thing has happened is when Im going uphill (very steep) and from that point on I have to drive at 70mph or slower otherwise the temp start to rise. At that speed the coolant temp. is reading between 200f and 210f which i believe is still too high but the temp. needle doesn't move. 
I have no problems whatsoever when driving in the city (is usually 55 or 65mph in the freeway).

I have no idea what could be causing it, I researched the forums and haven't found anything like my problem. There is no oil in the coolant/coolant in the oil, upper and lower radiator hoses both get hot, and only seems to happen when driving faster than 70mph or when rpms stay higher than 2900 for some time. 

Does anybody have any idea what could be wrong?


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## skeeter123 (Apr 30, 2010)

What model? What engine? What mileage? Could be your thermostat is stuck partly-open; maybe time to replace it. When you changed the coolant, did you bleed the system? Could be air pockets in the cooling system.

Hey, maybe you've got road kill or MacDonalds wrappers caught up in your radiator fins, check to see the airways into the radiator aren't blocked. Just trying to think of ways that ur cooling system could work partially, but not enough for high-load conditions.


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## pepperjack13 (Jun 20, 2010)

jaja no the radiator is clear, sentra 97 1.6 with close to 163000 mi. Yes I did bleed the system. I thought that it could be the thermostat too but since it only happens in high load conditions like you said, I am not entirely sure. 
The first time it happened I thought it was the transmission but there was no noise and the car was already in fourth gear (tried to turn on and off overdrive but it made no difference). Since i never had overheating problems before is it normal for the car to lose power?


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## smj999smj (Jan 1, 2006)

I would use an exhaust backpressure tester to check for a partially resticted catalytic converter. If that was okay and the engine is in proper state of tune, I would do a cylinder leakdown test to check for a possible failing head gasket.


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## pepperjack13 (Jun 20, 2010)

I guess I am going to start with the most likely, the thermostat. If that doesn't fix it I will take it somewhere and have them do what smj999smj suggested.


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## skeeter123 (Apr 30, 2010)

FYI my daughter's 98 Sentra GA1.6L thermostat stuck, I replaced it. Not as hard as some of the posters griped about it, but it is a little hard to get to (on the firewall-side of the engine, held on by three bolts, one of which you can't really see). I found that some of the parts stores were only stocking the 180 deg thermostat and calling that OEM replacement; but the FSM called for the 170 deg. I'd make sure you get the 170 deg thermostat, it made a difference for me (always runs a notch below 1/2-way mark on temp gauge). I think I remember that the thermostat had a little bleeder-thing built into it, that should be positioned at the top when you install it. It's function is to prevent air pockets from forming. Also, check the radiator hoses/clamps, I found that the OEM clamps had slow leak/crud buildup around them. I removed them, wire-brushed the dried-coolant off, and replaced the clamps with the worm-gear/screw-on type. No more leaks!

Oh, check the top of the alternator for evidence of dried-up coolant, that's what clued me into having the slow leak.

And I don't know if the overheat is causing the power-loss, but maybe if you clear up one problem the other will go away...
Hope this helps.


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## pepperjack13 (Jun 20, 2010)

hey skeeter123 thanks for the info but where did you buy the 170 thermostat? I was thinking of going to autozone today and just get one since I want to replace it this weekend. By the way, do you have to drain all the coolant? in my father's van you can replace it without draining it all.


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## pepperjack13 (Jun 20, 2010)

This is strange, I drove for 200mi and through the same mountain again yesterday, with the car's rpms at around 3500 for some 10-15 minutes, and the highest temperature I saw the coolant reach was 192f. I was very surprise it didn't even got to 200 like last time. Maybe it has to do with temp outside, this time it was 95 (it was at night) and when I have had this problem before it has always been like 110f and at around 2pm. I don't know if it fixed itself or if it didn't happen this time because wasn't as hot outside.


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## skeeter123 (Apr 30, 2010)

Got 170-deg thermostat at AdvanceAuto; A-Zone should have it.

Have you verified fan comes on when engine hot? A quick check is to turn on A/C, fan will come on when you turn on A/C. Longer check is to let it run/rev it till temp gets up, see if fan comes on. Could be the ECT engine coolant temp sensor, but usually if your temp gauge is working the sensor is OK.

PS I still think it could be ur thermostat stuck partially open; open enough to cool until you really load it; and outside temp having big affect on it....sometimes they stick in one place for a while, then shift to stick in another. On such an older car, i'd just replace it.


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## pepperjack13 (Jun 20, 2010)

The one I bought from autozone is the 180 one you mentioned and I don't remember seeing a lower rating thermostat on their computer. I am going to take the 180 back and ask for the other one. 
I have checked the fans a couple of times and they work. Replacing the thermostat is a good start, too bad I am not going to have time to replace it for a couple of weeks


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## skeeter123 (Apr 30, 2010)

I drained & replaced the radiator fluid when I changed mine, so I don't know how much fluid will come out when you take off the thermostat, (but it won't be that much). I'd just take it off and let what comes out drain off, then fill it up as usual, fill the reservoir to the line, get it good and hot, then let it cool overnight and see if you need to put more into the reservoir the next morning. I kept an eye on mine for few days, to let it go through a few warm-up/cool-down cycles. As the system cools down, it will suck in any additional coolant it needs from the reservoir.
My old thermostat was visibly deformed, I could see that the "plunger" part was off-track/cockeyed, not seated properly and hence always part open.
I re-checked the FSM, it calls for the 170-deg thermostat, with the bleeder "jiggle valve".


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## STEALTHY SENTRA (Sep 1, 2009)

haven't changed coolant in five yrs.? I suspect radiator coolant passages clogged with deposits,also affecting the thermostat! i call that "auto abuse".


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## pepperjack13 (Jun 20, 2010)

Yeah I couldn't believe it either but I just don't remember ever changing the coolant and who knows how long it had been since the previous owner did. Good thing it never gave me any problems until recently


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## jdg (Aug 27, 2009)

Both my '97 Sentra and my '98 200SX had 195F thermostats in them. I am the 2nd (3rd, 4th, whatever) owner of them, and got them at 140K and 70K miles respectively, so it's entirely possible that the previous owner swapped thermostats.
One thing I did learn right after I got the '97 2 years ago...the thermostat gets installed with the 'jiggle valve' facing as much UP as any particular installation will allow. Took forever to bleed the air out of the cooling system with it facing downwards. Piece of cake once I spun it around a bit.

And as far as the shops not having a particular thermostat...
That's the problem with having punk kids working behind the registers. All they know is what the computer tells them. They won't expend the 20 seconds of effort it takes to realize how things are set up on the shelves.
At all 3 of the local shops I get parts at, the thermostats are all located in one section, sorted by size, and by temperature. Small diameter to the left, large to the right; colder up top, hotter at the bottom.
If you want a small, cold thermostat, it's upper/left. You want large/hot, it's lower/right. Piece of cake. But apparently the concept escapes all but those with shred of common sense.


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## slwd2121 (May 14, 2012)

pepperjack13:
Some Nissan Vehicles, like my 06 Titan have an Engine Protection sensor. When the coolant temp. pressure becomes to high, usually on hills and do to outside temp. The temp. with raise quickly and the engine with go into its protection mode. That is where your loss of power comes into play. No matter how much you give it gas, you'll lose power til the temp. pressure comes down, usually when you get to the top of the hill. Read the Owner Manuel, its in there.


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## pepperjack13 (Jun 20, 2010)

slwd2121:
Maybe that's what caused it but I couldn't find anything on the manual, and as far as I know it hasn't happened again since then (my gf drives it now). I did buy the thermostat and if it happens again I will install it.


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## Nz Nissan Homy 1996 🥴 (Dec 16, 2020)

skeeter123 said:


> I drained & replaced the radiator fluid when I changed mine, so I don't know how much fluid will come out when you take off the thermostat, (but it won't be that much). I'd just take it off and let what comes out drain off, then fill it up as usual, fill the reservoir to the line, get it good and hot, then let it cool overnight and see if you need to put more into the reservoir the next morning. I kept an eye on mine for few days, to let it go through a few warm-up/cool-down cycles. As the system cools down, it will suck in any additional coolant it needs from the reservoir.
> My old thermostat was visibly deformed, I could see that the "plunger" part was off-track/cockeyed, not seated properly and hence always part open.
> I re-checked the FSM, it calls for the 170-deg thermostat, with the bleeder "jiggle valve".


Well for me today .. my fab mechanic noticed that with my over heating on hills especially Nissan Homy camper van .. The lower hose to the radiator was sucking in and causing a blockage as the hose sealed in on itself .. As it was so old and worn .. so he had a new one there .. popped that on and it’s fixed ! Runs way better even on the flat roads . They tested it on a hill and it’s gonna be the simple answer to that loosing power in hills and over heating issue !! Just saying !!! And as it took 8 days to figure that out .. I thought I’d share that news 🥴👌🏼🧚🏽‍♀️


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