Bad thermostat or coolant temp sensor?

[3echo9]

Temp gauge rises and falls while driving instead of rising gradually and stabilizing.

Noticed the temp through the heating vents goes from hot to cold and back to hot as the car moves.

Cooling fans are also coming on and staying on..in this 30-40 degree weather.

Noticed that the reserve tank was low and added a 50/50 mix to bring it back up to the cold level.

Checked oil..doesn't appear contaminated with coolant. Exhaust has no coolant smell.

So, anyone want to take a shot? I'm leaning toward the coolant temp sensor but not sure if it does anything other than read temp and whether it's output would effect the other symptoms.

[brcidd]

Well, you've pretty well got the symptoms down.....number one cause of loss of heat is low coolant--you've confirmed both....I would not condemn temp sensor- it appears to be doing its job, reading liquid at times it is coolest and steam at time it is hottest....I'd get after you fill it up with coolant (radiator and not just reserve tank)- that temp doesn't swing until coolant gets low again.

All the above says you have a leak- for your sake. we can all hope it is external. So look back after everytime you park it, look under it everytime you drive it away- look for puddles and specific puddle location- then trace it back to engine or engine component.....

If not external- then by all means quit driving and get it analyzed soon- the worst thing you can do is be dumping coolant in the oil and cause severe lower engine bearing (rod) damage.

[3echo9]

Thanks, for the reply brcidd. I haven't spotted any puddling under the car as of yet and my wife who drives the car hasn't really thought to look before now. Could a bad thermostat cause fluid to escape? This happened a few weeks ago when I refilled her overflow tank thinking the low fuid level was the issue. But now that it's happened again I'm wondering 1. leak 2. bad thermostat causing the car to heat up too much and overflowing the coolant resevoir while she's driving

[brcidd]

A stuck thermostat could cause fluid to escape -- as in a boil over. Your wife should have noticed any temp guage red zones, or hot lights, or steam- if that were the case. Check the radiator coolant level if possible, not just the burp box.

[inafogg]

its going some where, what engine ?? did a search,not much....
can you check the rad or is there no cap
pressure test its leaking some where, sounds like air in system now but
it had to run low for this to happen
Good luck

[3echo9]

3.4L, no radiator cap, just the one on the overflow tank...

She did have some temperature light warnings with the gauge bouncing from the red zone back to normal. The million dollar question is which came first? The low fluid level or the stuck thermostat.

Just picked one up at the local Autozone and a bystander commented that newer thermostats are designed to fail in the stuck open position. Does anyone know if that's true. If it is I don't see how the car would ever overheat.

I think I'll replace the thermostat just to be safe and go from there. Wish I had the service manual for this car.

[brcidd]

Low coolant can cause the gauge bounce into the red zone--

But if you still want to change thermostat- it can be a PITA- with that exhaust crossover pipe in the way. The service manual says to remove it, but I have gotten around it before- can take a while, - but you need to know where the coolant is going... I'd be looking at the first drips that come out of that oil pan on next oil change (soon).

[3echo9]

Thanks, I took a look and it it appears like I should be able to get an open end wrench on the back bolt. The cross over pipe shouldn't get in the way of the forward bolt.

I put more coolant in the over flow tank and the overall temp has evened out but now I get a definate coolant smell in the car. Don't know if its from leaving the overflow tank open for a bit to see if the fluid would get drawn into the system while I added coolant to the car as it heated up. No wetness on the passenger floor. I had to put the cap back on as the level kept rising. I guess that could prove there's a blockage or a thermostat stuck in the close position. The return hose didn't seem to get as hot as the supply hose either.

I'll give it a shot this weekend. ATV sealant on the bolts?? Necessary or not?

[3echo9]

Good news and bad news.

Found out what the oder was...the good news...it wasn't coolant.

The bad news...we aren't having fish-n-chips this week. The wife left the fish in the car from her last trip to the grocery. Ironically the smell started the morning after I put more coolant in the car.

Going to replace the thermostat this weekend....and go to the Legion Hall for the fish.

[3echo9]

Thought all was good to go...

Wife brought car home last night with a ticking noise coming from the engine. She couldn't replicate it for me when she got home with the engine still hot but later we started once the engince cooled down a bit and there is a definate 'ticking' sound that speeds up with the RPM.

I had noticed a slight ticking before but not as loud as it is now.

Oil level was good.

The car's temp had gone into the red a few times over that past few days with the issues we've had but not to the point where I would have thought damage to the UIM would have taken place.

Anyone have any thoughts..wondering if the water pump would make this kind of noise if it was failing? Going to try to take the pump out of the loop to see if the noise goes away by taking the off the serpentine belt.

We'll see...just spent $500 on parts for the 99 Grand Prix...not really looking to rebuild this 2005!!!!

[3echo9]

Car overheated again after spending $1200 at an independant who said their wasn't a cooling problem. He fixed the wheel bouncing issue by putting in a new steering rack.

Took it to a dealer for this problem. And another $1200 later we have a new LIM gasket put in. Does this sound reasonable to any GM dealer folk?

Here is a parts break down.

Sealant X 1 $19.32
Seal X 1 $3.89
Gasket X 2 $61.70
Thermos X 1 $30.94 (nevermind that I just put a new one in three weeks ago for $10)
Seal X 1 $15.10
Seal X 1 $16.31
GSKT KIT X 1 $212.27
Total parts $358.53

Individually I don't have a problem but what does the KIT have in it if not all that preceeded it on the detail breakdown?

P

[Ruley73]

Originally Posted by 3echo9

Car overheated again after spending $1200 at an independant who said their wasn't a cooling problem. He fixed the wheel bouncing issue by putting in a new steering rack.

Took it to a dealer for this problem. And another $1200 later we have a new LIM gasket put in. Does this sound reasonable to any GM dealer folk?

Here is a parts break down.

Sealant X 1 $19.32
Seal X 1 $3.89
Gasket X 2 $61.70
Thermos X 1 $30.94 (nevermind that I just put a new one in three weeks ago for $10)
Seal X 1 $15.10
Seal X 1 $16.31
GSKT KIT X 1 $212.27
Total parts $358.53

Individually I don't have a problem but what does the KIT have in it if not all that preceeded it on the detail breakdown?

P

An educated guess is that the kit would either be the upper or lower intake gaskets; whichever isn't itemized by the detail breakdown.

Is the problem fixed? If not, I'd be pretty upset. FYI the design of the intake manifold is different on the China-built LNJ 3400 engine that comes in the 2005-2009 Equinox/Torrent. It is not plagued with the intake gasket issues of the older LA1 3400 that came in other older GM models. Yours would be the first I've heard of with intake manifold gasket issues. With that said, this does not mean it is impossible for these gaskets to fail in this engine.

I just wanted to point out that it is not a common issue with this engine, so make sure they didn't just simply take advantage of you.

[3echo9]

UPDATE: No the car is not fixed!! We just took it out for dinner...5 mile drive and the car overheated again. The temp gauge fluxuated between the first and third hash marks based on whether we were driving or stopped at a light. The dash temp light came on on two occassions. We just drove it back to the dealers' night drop with a detailed explaination of what happened.

Question one: how can a certified dealer make this kind of mistake? Aren't they expected to use there diagnostic tools to make correct judgements. They charged me $90 for the diagnosis alone. There expertise is the very reason I took it to the dealer and not a shop.

Question two: What, if any recourse do I have for either a refund of the work just done or the work yet needed to fix the original problem? In medicine you sue for malpractice. As I stated to the dealer I was certain it was not a coolant leak because I found no coolant in the oil. His statement for the repair was that their was a failed gasket and that coolant was mixing with the oil. And his evidence was an empty overflow tank.

I still think there is either a block somewhere in the system or a innoperable water pump. The fluid is not moving in the system causing the temperature to fluctuate with the movement of the car until the engine heats the fluid too much as movement through traffic no longer cools the engine enough. Is there a way to check if the pump is adequately moving fluid?

Thanks

[Ruley73]

Originally Posted by 3echo9

....Anyone have any thoughts..wondering if the water pump would make this kind of noise if it was failing? Going to try to take the pump out of the loop to see if the noise goes away by taking the off the serpentine belt.

Did you ever try this? Changing the water pump should be pretty easy. However, I noticed they don't use the exact same cheap water pump as the older 3.1/3.4/3100/3400 engines. It is pretty much the same except the impeller has a different pattern with more fins and appears to be more shallow as well. A brand new AC Delco (p/n 252721) water pump can be shipped to your door from www.rockauto.com for under $30. Expect to pay at least double that from your local parts store and it probably won't be an AC Delco. The brand of your water pump isn't big deal though.

Did you ever try replacing the coolant temp sensor? That is another cheap & easy fix. This part can really wreak havoc if it is bad.

One last thing that might cause the cooling system to boil over is a bad coolant lid that isn't holding pressure. Hint: your "overflow tank" is actually a pressurized reservoir.

[inafogg]

I still think there is either a block somewhere in the system or a innoperable water pump. The fluid is not moving in the system causing the temperature to fluctuate with the movement of the car until the engine heats the fluid too much as movement through traffic no longer cools the engine enough. Is there a way to check if the pump is adequately moving fluid?

Thanks[/quote]

the only way i can think of is to open the bleeder valve by thermo housing.with engine running you should have a pretty strong flow.
there should be another bleeder around the water pump.i'm curious
as to what the dealer has to say,something like there was air trapped
in the system.

has anyone verified that the radiator cap is ok. as mentioned before if
its not holding the system pressure,you may be loosing coolant out of the top of resivour and may not see it.this would take awhile & not the reason its overheating now but it could of been the reason for the original trouble.
while at the dealer ask them to check the cap!!and watch them do it