Hey gang - 88 TPI. what did I do wrong here? My car runs great and stays at a good operating temperature when driven. Two small issues I had were no heat inside, and if it idles for LONG periods without moving (e.g 20+ minutes), the engine temperature starts creeping up. So I decided to change the thermostat (Advance Auto) today to see if that would resolve the issue.

I found some useful tips from various posts on here which made it seem pretty easy. Removed the upper radi hose and let some coolant drain out. Removed the throttle body and thermo housing. Removal went fine. Installed a new thermostat and gasket, and reassembled everything.

Started the car with the radiator cap off. I added a bit of coolant (wasn't overflowing), closed the cap and let it idle with the heat on. The car started warming up after a a few minutes and then the temperature started rising rapidly (still no heat inside). Took the car for a quick ride around the block to see if that would lower the engine temp, but it went up to near red.

So I immediately parked it. The upper rad hose felt a bit warm to the touch, but not hot. Thinking maybe I didn't put enough coolant in, I carefully opened the rad cap and it immediately started shooting coolant out (and thus I closed it immediately)

So now I am sitting here waiting for the car to cool down. I did notice a few minutes after opening the cap the upper rad hose was now much hotter. But there were no leaks around the thermo housing or hoses. So it looked like my connections were good.

What did I miss here? Everything seemed to point to a very simple process - remove thermo, replace with new one, add coolant, drive car. Was there something in this process I missed? Hoping you guys can help.

 

You might have had a big air bubble in the system that needed burping. You can add coolant to the overflow tank while the engine is hot and as it cools down it will inhale the coolant. I would let it cool, top off the actual radiator and leave the cap off while you warm it up. When the thermostat opens, you'll see coolant circulating. If it starts to look like it's getting too hot, but still no circulation, rev the engine a few times and see if it burps. Until you reprogram the ECM or add another temp sensor in parallel to activate the fan at a lower temperature, it will still climb to ridiculous levels before turning the fan(s) on.

 

Thanks. I'll definitely let it cool a bit and will check the overflow tank in hopes some coolant was taken in. When you see I'll "see it circulating", do you mean this: when i opened the cap upon first starting the car, coolant was flowing. I could see it coming out (with force) of that small hose connected to the top of the radiator. I didn't think much of it since that's what the car did before I changed the thermostat. Is that the flow you're referring to?

Oh - and the fan was hard wired to remain on all the time (previous owner).

 

No, that would be boiling over basically. You should see coolant just sort of flowing along from left to right (from passenger's side towards driver's side). You have more than just water in there, right? The water pump needs the lubrication. When it's flowing the top hose should get pretty warm.

 

OK. Yeah - it's definitely coolant (50/50 mix). Perhaps I'm seeing the coolant shooting out of that small upper hose on the passenger side because the radiator isn't full enough. I'll be checking it again in just a bit.

 

You DID put the new thermostat in right side up , yes ?

There is a specific direction it's gotta get put in at , and I think it is possible to put it in upside down . If it is upside down , it'll need to be taken out and reinstalled correctly ....

 

Well I just tested it again. Same result. This time I didn't drive it at all and just let it idle. I even followed the Haynes instructions to perfection. With the Rad cap open, I started the car and let it warm up. (The radiator was definitely full, and did take some coolant from the overflow tank while it was cooling down before.) But again - the temperature just kept creeping up and up to the red. And again, the upper rad hose never got HOT. Just warm. I eventually just turned off the engine.

It's a Superstat thermostat (installations instructions below) model 5653576 from Advance Auto. I'm confident it's installed correctly per the instructions. When i was watching the coolant in the radiator, it was 'swirling' if that makes any sense. It didn't look like it was flowing from passenger to driver side as you suggested earlier afremont.

Any other suggestions gang? I'm this close to re-installing the old thermostat. I've done NOTHING else but a simple swap...and now I'm met with more problems than when I started. Thanks again for any help you can offer.

http://stant.com/repository/files/Ba...tructions1.pdf

 

Try disconnecting a heater hose at the intake to let the air out.
Do you get any heat from the heater? If not then you have air in the system. Is the rad. fan coming on?

 

Ex fire ill give it a try. where would this heater hose be located? (and should I wait for the car to cool down again?) see above the fan remains on as soon as the key is turned on. No I still didn't get heat inside the car.

 

Take the thermostat out & test it on your stove in a pan of hot water. It may be new, but it could be defective. Never hurts to elimate it as a possibility.

 

Yeah - that's what I'm trying to avoid. It I take this all apart again, I might as well put the old thermostat back in. But if I do I will certainly test the new one as you suggested.

 

I just tried the whole process again. Cap off - started car...same result. Not cooling. I can say with certainty though - the upper rad hose never gets hot, nor does it get 'firm'. The side of the upper hose that's closer to the radiator is 'warm' to the touch. But the other side closer to the tstat is practically cold. Almost like the coolant isn't even reaching that side of the hose.

I think I found the heater hose you referred to exfire. It was right below the throttle body. I disconnected it and there was virtually no coolant in there. Is that normal?

The radiator is maxed out. I can't fill it anymore than it already is. I even tried squeezing all of the hoses to try and 'force' any air out. When i first start the car there are lots of air bubbles at the radiator cap, but then they go away after a minute or two...and I can't tell if that's air or just the swirling force of the coolant flowing into it.

If it is an air problem, would the problem go away if I just completely drain the radiator and refill it?

 

You got a bad stat. Used to be really rare, but nowadays 100% of them are Made In China.

The flow you see from the small hose connected to the pass. side radiator end tank is the RETURN hose sending coolant back from the heater core. It goes straight back down the end tank and up the big lower radiator hose to the water pump to be recirculated throught the engine again.

I "burp" the cooling system by leaving the cap off completely and waiting for the stat to open. When it does there is a big rush of coolant and air through the rad. It often overflows out of the radiator for a second or two and then that's it. It settles in and you fill it back up after that, put the cap back on and you're done.

However, if the upper hose isn't getting hot no matter what, the stat isn't opening. Period. End of sentence. Even if you don't follow my procecure for burping the system, they will self-purge no matter how screwed up the procedure you use. Those systems are extremely well designed from the factory. If all the factory hoses are in place (not blocked off here and there for whatever reason) they will almost always self-purge.

 

+1 for boiling the old t-stat after removal and the new before install. Bet the old one is good.

 

it is also possible that you could have installed the thermostat "backwards" which would restrict flow.

 

Thanks for the advice guys. Looks like I will be taking he new one out and putting the old one back. What a fiasco. I will let you know how the reversal goes.

 

On some models, there are clear "Front" indicators. Some models are hard to tell. If you'res isn't so marked, spin the new thermostat 180* in place before you take it out. Just to see if you accidentally put it in backwards. I did this on mine when i did my engine build and felt really stupid when I was shown what I did wrong. On the plus side, Mr. Gasket thermostats are all labled "front", with an arrow! hahaha So that's all I use now.

 

I've had a few defective name brand (Stant) and OEM thermostats out of the box.

 

I've had a few defective T-stats over the years too but I was always able to spot it by boiling it in a pan of water. If its not in upside down or backwards, it is probably bad. That being said, his original problem was the car heats up when it idles (I think all of the stock ones do that) and that there is no heat from the heater core. If all else is/was ok he could have a bad heater control valve, clogged heater core or some other mechanical malfunction.

 

Thanks guys. I plan on trying to tackle it again tonight or tomorrow and will definitely so the boiling water test. OZZ - do these thermostats have to be installed in a specific 180 direction? I was under the impression that as long as the spring side is down, it shouldn't matter. Plus I don't recall seeing an arrow to indicate front vs back

 

You can try the pill trick. Take an aspirin & wedge it into the t stat, this helps get rid of air pockets & the aspirin will dissolve.

 

The only concern on these is up or down. There is no front/back/left/right orientation to contend with.

 

Yeah that's what I thought.

So tonight I took the new Tstat out. I placed both that one and the older one into boiling water. both opened...though I did notice the older one opened a bit sooner. And I don't know if it makes a difference, but the new Tstat has a much smaller opening for coolant to flow through.

Long story short I put the old one back in and viola - car runs fine. I still have no heat but at this point I will just savor the "victory" and research other causes for no heat later. But thanks to all of you for your help. I will be returning the new Tstat first thing tomorrow.

 

How much sooner did the old one open?
Are the heater hoses getting hot? If its just one side, then take a garden hose & flush the heater core both ways.
I'd get another new t stat & try it again, remove either a heater hose or coolant sensor (to let the air out as you fill it), get one of those funnels that snap in to the rad. Fill til the coolant trickles out of the hose connection/sensor, tighten up the connection. Start up & hold rpms up around 2k & coolant level should drop when the t stat opens. Continue holding rpms while putting rad cap on.