thermostat question
 

First, I've done some searching and am pretty sure i've found my answer but really just want some verification before i take the car out again, as its on a fresh engine and i'm trying to be very careful.

It was pretty cold here today, 40 degrees F or so. I started the car, and sat there to let it warm up. man does it take forever. after almost 10 minutes the stock temp gauge was half way up. but my a-pillar gauge still wasn't reading anything. since it had been quite a while i coasted out of the driveway and started to put down the street, all of a sudden the stock temp gauge went up to about 3/4, i got worried so just coasted for a little bit. then i limped it home, terrified, still no reading on the a-pillar. as soon as i stopped in the driveway the A-pillar gauge shot up to about 180 degrees F.

I've read that this is b/c the thermostat just opened. But why would my stock temp gauge spike up to 3/4 before it opens?

Also, my TEC GT ems coolant temp sensor is in the same location as the a-pillar gauge so it doesnt run very well until T-stat comes open (it hasn't been adjusted for NY weather) it was originally tuned in VA. So I know that i have to spend some time adjusting the warmup fuel tables. but this doesn't explain why the stock temp gauge goes to 3/4 before opening the Tstat. is this normal and i just haven't noticed it before because it's never been this cold since i've had it? or is there a problem with my Tstat.

Oh and after it opened, my temp stayed fine the whole night. but it seriously took about 10-15 minutes for it to open.

curious as well. I only have my stock coolant temp gauge, and it randomly spikes up and falls

Stock gauge should never go above 1/2. Most likely it is sticking or you have a flow restriction somewhere. The reason your aftermarket gauge reads late is most likely because of where the sensor was placed.

I mean the thermostat is sticking, not the gauge.

I actually JUST replaced mine, and nothing changed.

I definitely understand why the aftermarket gauge acts like it does, there are several other cases documented on here, its because the sensor is on the front of the thermostat cover, and doesnt get a reading on the temp until the Tstat opens.

Boostscoop, were you seeing the stock temp gauge spike to 3/4 or all the way up before opening? and is the Tstat controlled by a sensor or pressure. if its by a sensor then mine wouldn't be sticking, it would just be waiting for a high temp to open the tstat.

but if its pressure, it may be sticking slightly, and then the pressure builds at the higher temp - the 3/4 reading on the stock gauge, which then forces it open and it then operates normally. any thoughts? I'd like to figure this out before i start it again and risk an overheat.

Could an air bubble be causing this? I've burped the system with a funnel in the filler a few times now. Also, i have a crack on the neck of the overflow resevoir, can this cause a problem besides it leaking from the top if it gets full?

i definitely won't move it again until the tstat opens and i have a reading on my aftermarket gauge, its scaring being a half mile down the road and seeing the stock gauge hit 3/4 and the a-pillar at 0.

+ 1 for replacing the t-stat.
And if you still have the throttle body coolant line, I'd relocate the aftermarket gauge sensor in there. It's easy but you can search under related term in threads by DaleClark for the "how-to".

I have no throttle body coolant line on my setup.

i started it again last night, same thing happened, took about 15 minutes for the stock temp gauge to get halfway up. around 20 minutes it spiked, i checked the radiator hoses and they were still cold, but had a ton of pressure, i could barely squeeze them. as soon as the Tstat opened everything went back to normal.

is there a sensor somewhere for the tstat that could go bad causing it to open late?

From your description, it's almost certainly a sticking thermostat. The thermostat is totally independent, and operates via a wax rod. They are cheap and easy to install. Use the OEM thermostat only.

Paul

Ok, I'll be changing the Tstat then. I still have the old one sitting in the original engine. is it ok to try this one or should you always go new when putting in a Tstat

Use a new OEM thermostat, they're not very expensive. There are numerous reports of aftermarket thermostats sticking or not blocking the recirculation bypass correctly.

Search for "OEM thermostat" and you should find a few threads about it.

Yeah, i've read about the aftermarket Tstat problems, i'll def be going OEM, i know the one in the old engine worked fine. I was only considering using that b/c i was planning a trip this weekend and would need to have it swapped tonight, and i won't be able to get a new one fast enough.

has anyone swapped a tstat from one engine into another, or when someone gets a short block do they always put a new one in.

I tested the old tsat in water on the stove, it opened at the correct temp. I put it in tonight, i'll start it up tomorrow and post the results.

Tstat change did the trick, it opens up normally now, and the A-pillar gauge eases up the whole way to about 160 then shoots up to 180, and the stock gauge no longer spikes. Thanks for the help everybody.

I started the car today and it started acting the same as it did before i switched the Tstat. it was fine all day yesterday.

Today i started it up after sitting all night and it had the old symptoms. then after it was fully warm i stopped to get groceries and that took about 45 minutes. i came out to the car, the a-pillar was reading 145F, and in about 2 miles it was still there and my stock gauge spiked really hi, after a few minutes the Tstat opened and the apillar gauge went to 220 and came back down to 200 pretty quickly and the stock guage went back to half way up as soon as the Tstat opened.

Can an air bubble be causing this?

IMO, yes.

Is it possible that you have a problem in the coolant recovery system such that water doesn't get pulled back to the engine as it cools?

Leaky coolant caps are often to blame for this, as are restrictions or leaks in the coolant recovery tubing.

Dave

this really scares me because my 1st impression is "OMG MY CAR IS OVERHEATING" is the temp sensor reading the water temp of the motor? or of the radiator? kind of consufed...

where's my parts i bought from you???? please respond to my pm's thanx

Could a radiator hose have failed and collapse internally somehow...and coolant is flowing only once enough pressure is built up?

I think there may be a problem with the recovery system. i can fill it up, and then after i've driven, and then let it cool down and sit, its not full to the cap anymore.

I don't think anything is wrong with the hoses, once the stock gauge says its about to over heat and the a pillar gauge is still 0, the radiator hoses are full of pressure, not collapsed. I can barely squeeze them, but as soon as the tstat pops open i can squeeze them.

and boost scoop, it is scary, i pretty much overheated today coming home, the a-pillar gauge is on the side of the tstat housing that doesnt get water until it opens, the stock guage reads off the block, so the coolant in the block overheats and the fluid in the radiator cant get in to cool it off until the tstat opens. and its opening very late.

i'm going to detach the hose that goes from the bottom of the resevoir to the tstat housing and blow through it with an air gun. any other ideas? when it was really hot today, I pulled up a little on the red release of the radiator cap and it hissed and then shot some fluid out, does that mean its ok?

1. Possibly a sign of coolant recovery not working properly, but could also be a sign of the start of coolant seal failure - combustion gasses getting into the coolant. You can do a hydrocarbon test on the coolant to confirm or reject this possibility.
2. Not necessarily. The cap can retain coolant pressure properly, but can still leak at the external seal (this often happens with lever-release caps - they often don't re-seat properly once the lever has been used), allowing air to be drawn back instead of coolant.

The fact that the thermostat operated properly the first time after you replaced it and purged air from the system is, IMO, definitely a sign that air is getting in somehow after running the engine and causing the problem.

Dave

Thanks Dave,

I'll get a new cap, i think you're right about air getting into the system. I really hope its not the coolant seal, it has gotten hot, i hope i didnt ruin my new motor already.

Any notes on how to do the hydrocarbon test? also, the coolant only has about 350 miles on it, will that short of a time allow it to retain the hydrocarbon to make the test accurate? sorry if thats a stupid question, just haven't done one before.

If its not the motor, i think the only items that can be effecting the recovery system are the cap and the hose that goes to the bottom of the resevoir. Is there something i'm missing?

1. Good start - get a standard 13-psi cap (no release handle)
2. I've never done one, but I've seen several posts on the hydrocarbon test (a radiator shop or a good repair shop would be a good start to find someone to do it)
3. Reservoir itself could be clogged by crud at its bottom, letting coolant in but not out to return to the engine.

My vote is for air in the system that wasn't removed when you did your thermostat replacement. You may also have a slight leak that is hard to detect. A cracked or split in a hose could allow coolant to escape, and air to be draw into the system instead of coolant from the overflow tank. A pressure test may help to find an external leak if one exists. If I were you, I'd work on getting air out of the system by squeezing the upper and lower radiator hoses with the filler neck cap off. Squeeze the hoses until you don't see anymore bubbles. Top the coolant off at the filler neck, replace the cap, and run the car through a few heat cycles. Repeat this process until you get no more bubbles or you don't have to top the coolant off anymore. If you get rid of all the air in the system and you still have problems, then I would look to the pressure or hydrocarbon tests.