New thermostat doesn't want to open while car is running

[GooeyGus]

Hey Guys,
I installed my new fluidyne radiator today, and also installed a new temp sender for the gauge, and a new thermostat. Temperatures were fine before

Now when I drive the car, the needle climbs up to about halfway between the "water temp" symbol and the red zone (or about 3/4 of the gauge). At this point I shut the car off and pop the hood and run around to check things out.

The top of the radiator is still cold, but as I'm holding the upper hose I feel the bottom of it begin to get warm, and then the whole thing gets warm, meaning the thermostat is flowing.

This was the first time I fired it up after I installed everything, so I proceeded to burp the system and I figured it was a fluke.

I went to go get dinner a few minutes ago and the same thing happened. I pulled into my destination (only about 2 miles away) and popped the hood. Top of radiator still cold, but as I'm there feeling it the thermostat opens and it warms up.

So I then drove home (after the car sat about 5 minutes) and the temperature was ok, just a little bit past the middle, but it has ALWAYS sat about 1mm below the middle.

I think the thermostat is not opening all the way.

What can I do? I've never had a thermostat act this way before. I think if I just let it keep going, it wouldn't have opened while the car was running.

I'm pretty sure I installed the thermostat correctly, as I think it will only fit one way. BUT just to make sure, the larger part of the thermostat should face down towards the head, and the smaller 'point' of the thermostat should face the upper rad hose, correct?

I guess tomorrow I'll just put in my old thermostat

 

[steve]

Is the new thermostat OEM?

 

[badabing33a]

Yea put your old thermostat back in. Since it worked before, it should still work now. Hopefully that's what your problem is. I would take your new thermostat back and return it. They should give you another one depending on where you got it.

 

[FullMetalJack]

the spring side goes towards the engine. And if the radiator is not hot yet the temp sensor says the engine is hot then the thermostat is most likely stuck closed.

 

[GooeyGus]

I drove it around a bit more, and although it is a bit better, it's still not what I'd like to see. The needle is basically straight up and down while driving now, covering the "coolant temperature" symbol. Before it has always sat just barely to the left of the symbol. The only two variables here are the thermostat (which is what I'm leaning towards) and the new sending unit for the gauge possibly indicating a bit higher than the original.

I'll swap out the thermostat tomorrow morning and report back.

Oh, and no the thermostat isn't OEM (but it SHOULD be OE temperature). I got it at schucks/o'reily. I even paid the extra two dollars for the "premium" thermostat!!!

I did notice that with the old thermostat (which is only about a year old. I just figured I should change it while I'm in there) at room temperature if I forced it I could open it myself. With the new one, it would not even budge. Also, the older thermostat is marked as 195 degree. The newer one is marked as 192 degrees... hmmmm.....

It seems I can just never win with this car!! I give it a nice new radiator and the thermostat acts up!! haha... Oh well. At least my compression test showed 150 across the board; not bad for 204,000 miles. *knock on wood*

 

[steve]

It's been years since I last tried something other than a OEM thermostat but what I remember is the aftermarket one having a much smaller opening. I only ran it for a couple of days before I went to the dealer and got the right one because it was causing the car to overheat.

If you one you have has a jiggler valve it's not right. The 1.8L uses it but the 2.0 stat pretty much fills the whole mount.

 

[wolfie359]

These issues are usually 1 of 3 thing.
1) Thermostat in backwards, pressure of it being hot and running is keeping it closed.
2) Air/Steam in the system, hot air doesn't open thermostats well... Bleed the system.
- Run water/coolant mixture to defend against boiling/steam, locking the thermostat closed.
3) Faulty thermostat, usually the most uncommon.

 

[rlacasse1]

Make sure it isn't upside down man. Sounds like that's the problem,

 

[jrohner]

Do you have access to a logger to see what the ECU says the temperature is? Did you change the right temp sensor? I believe 1G's have 3. Also, if the gauge sensor happened to be for a 2g instead, it would read higher than it really is.

 

[wolfie359]

If you have a doubt on your temp just to buy a digital thermometer with a range of at least 100 to 300deg, should run ya $20 at like target or something. Look in the cooking section. After you acquire one of those while your car is running check temps around your thermostat housing, radiator temp, ect, just be careful of the fans...

 

[proteusx301]

The symptoms of overheating and you feeling the hose get hot as the thermostat opens with the car off, sounds like you airlocked the engine. I would try to get the air out before going back into the system. This happens ocasionally to me at work, and purging the air from the system works about every time.

 

[GooeyGus]

All air has been purged from the system.

Yes, I changed the right temperature sensor. There are three, but the one for the gauge is the only one that is just one pin. Also, I'm 99.9% sure I got the correct sensor. I picked it out online myself and just gave them the part number (they said they had the same number listed for my vehicle) and it looked identical to the one that came out. As far as I know the 1g's and 2g's use the exact same sensor.

FYI, here is a picture of the sender:

You must be logged in to view this image or video.

My thermostat DOES have a jiggler valve. It looks like it should be there, theres a place for it to sit in the t-stat housing and everything. But, you know a heck of a lot more than me!

The thermostat is not upside down. The spring is facing the head.

I'm headed out right now to swap the old one back in. I'll let you guys know if it fixes everything.


UPDATE

Well I swapped the old one back in, but right when it got up to temperature the thermostat housing cracked and pissed everywhere. I think I overtorqued the bolts

Good thing I have my GSX sitting around... I went to the back yard and grabbed the thermostat housing off of that, went to shucks to exchange the thermostat and grab a new gasket.

I put it all back together, no leaks.

The final verdict:

I think the problem was a combination of both the thermostat not opening correctly and the new sender unit reading a bit high.

With the new thermostat, everything opens correctly and the needle is rock solid, but it still sits a bit higher than it used to. I will be getting some logging software very soon, so that should get to the bottom of it.

For now, I think everything is OK, the gauge sits about one degree past straight up and down, which I still dont like, but it's not moving and the car seems to be running fine. The biggest givaway is that the heat isn't blazingly hot like it gets when the car is actually starting to get too hot. The heat feels normal, so that's a bit of peace of mind at least.

 

[GooeyGus]

Well I have an official result.

The sender is reading a bit high. I used a calibrated, NIST traceable thermocouple in the coolant at work today. When the gauge is just barely past straight up and down, the coolant temperature is right around 190.

Moral of the story: use an oem sending unit for the gauge.

 

[wolfie359]

Cool, sounds like you got it all figured out..

reminder: mark your thread solved