Engine: Thermostat Operation

[wdills]

289 engine is getting hot when just idling.

I bought this NOS thermostat from SI before I rebuilt this engine because the car didn't have a thermostat in it. When I installed it, the thing ran hot. So I removed it and assumed the heating was due to the damage and corrosion in that old block, and the radiator didn't look very clean either.

Now I install the same thermostat into a different engine that I just finished rebuilding. I also had the radiator cleaned at the local radiator shop. After I solved the oil pressure problem I let the car run for a while to make sure everything was OK. The temperature never stopped climbing and I couldn't see any flow turbulence when looking into the top radiator tank. Coolant was sitting still like it was in a mud hole. I turned the engine off at 200 degrees on the gauge.

I pulled the thermostat and brought it to the lab guys at my work so they could test it. It is supposed to be a 170 degree thermostat according to the markings but it never cracked until it got to 182. The photo below shows how much it was open at 208. I have never had to test a thermostat before so I don't know if this is considered full open or not.



Is this as open as it gets or do I need another thermostat?

Thanks
Wayne

[Gunslinger]

A thermostat won't stop an engine from overheating...depending on it temp setting, it merely sets a level where it opens to allow coolant to flow. A low temperature 'stat won't stop overheating...it will just take a bit longer to get there.

Basically, a thermostat is there to allow the engine to reach designed running temperature as soon as practical. If the thermostat is defective, replace it. You might look into a thermostat that is designed to fail in the open position, so if it goes bad, the engine won't overheat to the point of damage.

[hawk gt 62 rhd]

I have a good thermostat from Gates it is 180 F ,the number comes tomorrow

[DEEPNHOCK]

Your thermostat 'looks' ok in that pic.
The fact that you either verified the temp it opens, of now know 'exactly' what temp it opens, is a good thing.
The blade need not go to 90 degree's for it to work properly.
Sometimes, no thermostat will cause overheating because, without the restriction caused by the thermostat itself, the coolant goes through the system 'too fast', and heat transfer does not happen.
200 degree's with the cap off is not an awful temp.
When you put the cap on, and have 6, 7, or 12 psi of pressure in the cooling system, it raises the boiling point higher than 212 degree's.
Running an engine too cool can cause oil related sludge problems.

[jclary]

We have had these discussions before. When you installed the water pump, did you use the proper thin water pump gasket? I have outsmarted myself before and made a gasket from too thick material. What this does is change the clearance in the water manifold for the pump impeller and it didn't flow enough water. Lesson learned.

Then there is the tale of some bad pumps that were circulating in the market a while back.

Once you reach the temp where the thermostat opens, you should see flow in the tank with the cap off.

Whatever solves your problem, let us know. There is always new things to learn. Good luck.

[E. Davis]

I have to agree with jclary. It sure smells like a pump problem to me. You should be able to see some circulation in the radiator the moment the thermostat opens. You should be able to feel heat in the radiator hoses if water is coming through. Not much help I guess but you have my synpathies for all the trouble you're having with that engine. Been there --done that myself.

[wdills]

It is a new pump and was installed using the gasket that came with the engine rebuild kit from SI. I guess I will run it without the thermostat and see what kind of circulation I get.

Thanks
Wayne

[Guest]

I was wondering what the water temperature is in the engine without referring to the dash gauge. In other words, using a candy thermometer in the water or an IR device. Just to make sure the engine is really overheating and not a defective sending unit or dash ground fault (common.)

But more alarming is that sooner or later, you should see water flow in the top tank. Finding why there is no water flow when operating temperature is reached would surely solve the problem. Presuming the gauge is in calibration and the thermostat is OK, I would seriously suspect that pump. There should be obvious water flow in the top tank. I am assuming your bottom hose is not being sucked closed by a missing spring.

Can the thermostat be put in upside down? I don't remember if you can even do that. I had an overheating problem in my '60 when I first got it which I thought was the thermostat. I was surprised to find it missing! The overheating was nonexistent, it was a bad dash ground to the gauge. A candy thermometer showed 170 degrees in the radiator.

[wdills]

Once I get the water flow issue solved, I will worry about calibration on the dash gauge and sending unit. I can have those checked at work too.

I thought about the thermostat being upside down, but when I removed it, I verified that the sensing bulb was hanging down into the water manifold.

Another thought that crossed my mind was, what if a piece of trash was blocking the little weep hole in the thermostat. Could the thermostat blade seal tight enough to create a trapped air pocket at the top of the water manifold, thereby preventing the hot water from reaching the thermostat? It would have to be an airtight seal or else the output pressure of the pump would eventually force all the trapped air through the thermostat and things would start operating normally. Just a wild a$$ idea.

Wayne

[PlainBrownR2]

Another thought that crossed my mind was, what if a piece of trash was blocking the little weep hole in the thermostat. Could the thermostat blade seal tight enough to create a trapped air pocket at the top of the water manifold, thereby preventing the hot water from reaching the thermostat? It would have to be an airtight seal or else the output pressure of the pump would eventually force all the trapped air through the thermostat and things would start operating normally. Just a wild a$$ idea.

If there's large chunks of whatever floating in the cooling system, there's bigger problems there than just a thermostat. That's a solution that, at the least, calls for flushing out the radiator and the block, because there shouldn't be any large solid pieces of any kind floating through the cooling system.

(Yeah yeah, I know guys, this would also call for popping the freeze plugs out and rodding out the casting sand still in the block, because of the remote chance something has broken loose and floated to the thermostat.)

[wdills]

No I don't think there are any large chunks of anything floating around. I was thing of something like a little dab of blue goo from a gasket installation. That weep hole is pretty small ya know.

[hawk gt 62 rhd]

Gates thermostat

gates TH 03182 G1 is aproper one, with weephole ,for the 289,thanks
dick waterreus

[rodnutrandy]

Thermostat problem

I am known for oddball solutions. I run a 180 degree stat that has a 1/8 inch hole drilled in the flange. That lets a little water flow always and trapped no air. after installing that stat ,my truck runs a good while under the 180 temperature and cruises right at 180 degrees, so it works for me.

[wdills]

Problem seems to be solved, but I still don't know what happened to cause it in the first place.

As mentioned above, the lab where I worked verified the operation of the thermostat. I liked Randy's idea so I drill the weep hole out to 1/8"

First I ran the car without the thermostat installed and verified I had good flow in the radiator. Then I installed the thermostat and let the car warm up. I watched everything very close as the temp came up. At about 150 degrees I could feel the bottom of the upper radiator hose starting to get hot, while the top of the hose was still cold. This told me that the 1/8" hole was allowing just a trickle of flow. Once the temp got up to 180 the entire upper radiator hose got hot, so I know the thermostat had opened. I could now see turbulance in the top of the radiator indicating flow. The flow increased and decreased with engine speed as you would expect.

I let the engine run for about 15 minutes and the temp held right at 180 as it should. Happy to have the issue solved, just wish I knew what happened last week.

Thanks for the input
Wayne