'00 SS... I replaced the thermostat hoping to fix an intermittent P0128 issue and now coolant is leaking from the therm housing. The therm came with a gasket and I also got another one separately and neither one fixes the leak. I put the old therm back in with the new gasket (old gasket crumbled but new gasket fits a little loose on the old therm but tight on the new therm) and it still leaks. The message center shows 'low coolant level' off and on a couple times during my 25 mile drive to and from work.

The therms look a little different... on the old one the functioning part is perfectly centered but on the new one (from a dealer) it's a little off-center. The dealership parts guy said they changed the design from what was originally on the car. If that's true then the old therm is probably the original and with it pushing 200k miles I'd prefer to go ahead and replace it.

Any ideas? Would replacing the removable part of the housing (I don't know what it's called) possibly fix it? Any advice is appreciated.

 

The secret to getting the thermostat housing to seal...
Is to be sure to get all of the old material scraped, ground off completely...
It needs to be a smooth mateing surface.... If the surfaces are clean and free of any debris.... you'll probably need to use some gasket sealer around the edges and on the gasket its self? Did you use any gasket sealer?

Maybe the Low coolant sensor is bad?..... That's why it comes on and off?

My low coolant sensor is bad... I just unplugged it and I just keep physically checking it out periodically. (Even though, I have no leaks)

 

A couple of leaks at the thermostat I've come across were due to a crack in the housing (bolts were over tightened) but the majority of leaks were because the housing was warped. In some cases the old housing was reused after 'resurfacing' the flange. Place a piece of coarse sand paper on a flat surface and use a firm, even downward pressure as you sand the flange. Continue sanding until all debris and minor pitting/scratches are removed and the surface is flat. Clean the housing and reinstall with a new gasket that has a thin coat of sealer on both sides. Tighten the bolts evenly and stop tightening when they are snug. If you over tighten them you can cause the housing to warp or crack the housing near the bolt holes.

Edit: When you refill the radiator make sure the bleeder valve on the thermostat housing is open. This will help to prevent air pockets when filling the system.

 

I didn't use any gasket sealer. Is there anything specific I should use to clean the surfaces? I'll probably get another gasket just to make sure it's clean before I put the sealer on it. I will also check the housing for cracks when I open it up.

I don't think the low coolant sensor is bad... it's never come on until this issue started.

Thank you both for the advice.

 

Clean the housing as I described above. The surface of the engine can be cleaned with a spray of degreaser/carb cleaner and a gasket scraper. Any stubborn debris left on the surface can be removed using a flat file.

 

I will give it a shot in the next couple days... fortunately I have something else to drive so it can sit and stay cool. Thanx again!

 

I had a low coolant light come on. the left side of my radiator had a crack in it. Cost 198.00 Parts and labor to repair. then the low coolant light would not go off. mechanic said it's the sensor in the radiator. 60.00 parts and labor. hope this helps.

 

Well... I seem to have solved the leakage problem with the thermostat housing and after filling the reservoir to the full mark (my manual says to fill the reservoir and NOT the radiator directly) I didn't see the 'Low Coolant' light at all on a 400 mile trip... but now it's off and on again. Now it looks like there's some leakage near the reservoir... after a drive home from work there was a lot of steam coming from near the reservoir and there is coolant around it. The car isn't overheating... it gets a little hotter when I'm stopped for a few minutes but when I'm moving the temp gauge is where it should be. I took a quick look and I couldn't see anywhere it might have been leaking from but I will check it out again when it's cool.

 

I haven't put any coolant in for a couple days and now the low coolant light comes on when I first start driving but goes out after a mile or so and doesn't come back on. When I got home this morning I kept it running and opened the hood. I don't see any coolant and there's only a faint smell. The level in the reservoir looks a little low. When I touched the hose that goes to the thermostat housing it's too hot to touch for more than a second (I assume that means coolant is running thru it ok) but the thin hose that goes to the reservoir is not near as hot. Could there be a blockage somewhere? Could that make the reservoir overflow somehow?

 

Low coolant light could just be a bad sensor. They get gummed up pretty easily. The sensor is right below the cap on the radiator.

The car can sometimes take a few runs to bleed itself of air. Could just be sucking in that coolant, I would fill the reservoir to where it should be