Can't keep a thermostat in it.

Ravie

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Thanks to Doug for helping me with my first issue on this forum. I've got another one for you that is stumping me.

When I first bought this car, the P.O's had done 2 separate Bar's Stop Leak treatments when they really should have just replaced the head gasket. They ruined the head in the process.

After I bought the car, I got a nice reman head from Odessa in TX, and of course new head gasket and various tune-up parts.

I don't remember honestly if it started happening right away or down the road, but what happens is, when the thermostat is in the car, before it has gotten up to op temp and started opening, a large amount of pressure builds up and it shoots out from under the "radiator" cap (I have the 2.0 where the cap is actually on the housing coming from the block itself)

As the pressure builds up greater, it shoots out with more and more force.

Now.

If I take the thermostat out, the car never builds up pressure and the cooling system runs coolant through with no problems. It cools the car well enough that it never goes over 100 degrees and never has any problems with pressure build up.

Last weekend I did a Hydrochloric Acid cleaning and cleaned it out very well with running water and then put new coolant in.

It made Zero difference.

Remember - all of this happens LONG before the car is actually over heating.

So what's the deal? why is there a problem with pressure when there's a thermostat in but not when there isn't? I would think if there was blockage, it'd be happening all the time.

Thoughts?
 

melsg5

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Have you tried changing the radiator cap for a new one of the correct pressure rating?
 

Ravie

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It looks to me as though the radiator itself has no cap. That is, it is sealed other than the upper and lower hoses.

The cap that is on the housing is not a pressured cap. It is merely a rubber seal riveted to the cap.
 

john.0_o

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I have a 90 Sunbird and the rad does in fact have a cap,it is located on the side of the rad on the drivers side.I think the one you are talking about is simply just to gain access to the thermostat.
Without the thermostat in,the coolant might not be getting heated enough to build any pressure but when you have one installed it gets hot and builds pressure and escapes through the crusty rust imbedded rubber seal on the thermostat housing cap?

Just a guess but that's what I would guess to be the problem.Maybe change both the rad and thermostat housing cap and install a new thermostat and see what happens.
 

92 Sunbird LE

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Even brand new stats stick, ( name brands included) Test on the stove in water with a cooking thermometer that its opening . ( well rinsed of course if exposed to coolant)


It also good to drill a small steam hole in the stat to release steam pressure.:)

Doug in P.R.:cool:
 

Ravie

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Even brand new stats stick, ( name brands included) Test on the stove in water with a cooking thermometer that its opening . ( well rinsed of course if exposed to coolant)


It also good to drill a small steam hole in the stat to release steam pressure.:)

Doug in P.R.:cool:

I did that just to make sure when I was messing with it the other day and it was working just as it should've been. I did notice it is missing the little rubber seal that goes around the bottom, but I don't see how even that would contribute to the pressure.

Interesting John, I'll have to look at that. I have not been able to spot one. It must be hidden in there pretty well.

All good ideas, guys. Thanks.
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Cam Gibb

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Puzzling. Stat housing neck cap leaks with stat in, not with stat out. Doesn't make sense to me. If each time you start with same level of coolant, reach same temp should be same pressure everywhere in system. But since it'll take longer to reach same temp with stat out, takes longer to reach same pressure of same temp it leaked at when in. Were you simply just not driving long enough for that temp to get as high with subsequent rise in pressure ? I found mine had less weak spot pressure leaks that took longer to happen if I had level about 1/2 way up the width of the big upper hose there. Bit of air space cushion slowing down pressure build up. Short trips to store it would be fine no leaks.
 

Cam Gibb

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I been experimenting with my exact same type and system. With stat in water pot on stove, I noticed it not opening til 90-95c. Too high. In car temp dropped on gauge when it opened at temp gauge showing 60-70c. I had asked for the summer one to open sooner for cooler running. So I played with it trying to figure out how the heck it works lol. That spring is attached to base but not the middle valve that moves. So boggles me but the spring must shrink when hot enough, allowing the valve to drop down. So I thought maybe shorten the spring so it allows drop lower temp. Using needle nose vice grips turned the spring so the bottom end of it comes out of frame below it. Got to point where it was loose with valve end so turned back in a bit. Tried in pot again. Watched temp rise. No diff. Since until a replacement is found it might be best to leave out. But then I wondered if cooling system design is meant to work best with just that 2mm circle opening when stat open. Allowing some coolant still forced from pump pressure, to engine top instead of no resistance allowing it all to rad and little if any flow to engine top. So it might be good idea until new one got, I will try, to wrap some wire, 1mm, copper, the thicker twist tie type, whatever, with the spring turned out enough for stat open, twist wire around the outside and inside of that ring of frame which will keep stat open but still provide some back pressure resistance for coolant flow to engine instead of just rad. YOU COULD SAY I HOT WIRED IT LOL. ;-) Like I had to when headlights and daylights stopped working. Had to get serious and look at the Chiltons wiring schematic. Figured out I could use 2 thick household extension cord wires, solder them to power source on headlight switch back side and to whewre they were shown to get power from the computer board up above driver feet area under dash. ;-) Watch for leaks that happen from small hose and clamp impossible to see from under hood, I think maybe it's a engine block to auto transmission coolant line for warmiong up tranny and keeping it temp from getting too hot. It's down under front bottom center to left but unseen from above below gen, heatwer hose connection, power steer pump and tension arm base and pully and serpentine belt. Without a ramp to get atleast 1 wheel up on or hoist, tight squeeze trying to get under there to see and check hose clamp for tightness and crack leaks under pressure.
 

melsg5

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Two things were sited in this 7 year old post. A bad radiator cap and the need to drill an air bleed hole in the thermostat. In addition using a 180 thermostat would be best.
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