I need help with a T-stat. Please

RickKlem · 10-26-2003, 06:04 PM

I have just completed installing a rebuilt 3.0L and it starts to run hot (240 plus) after about ten minutes of driving. I touched the font trombone cooler and both pipes coming from it and they are cold. I thought that the T-stat was not working properly so I removed it and noticed that both of the lines that go to the front of the car were full of oil. I guess that I was expecting them to still be dry, since the t-stat was not working.

My question is, on which side of the t-stat is the valve? I was thinking that once it reached it’s operating temp, it would open and allow oil to pass through the system. Now I’m wondering if the oil fills both tubes and then the t-sat would open allowing the oil back through the t-stat. But wouldn’t the oil lines to the front still be warm? Or the other thing that might be happening is that the valve is not opening all of the way, restricting the flow. But if that was true there still should be some heat on the tube. Why was there oil in the tube?

Also I have heard of people placing the t-stat in hot water and checking to see if it opens. Where are they looking to see if it’s opened? I have looked into the openings and I don’t see anything?

Help, I’m confused.

Rick

Chuck Moreland · 10-26-2003, 08:03 PM

The tstat valves off the return side. The supply side is wide open so you would certainly have oil on the supply side. Possibly the return as well, even a small leakage would soon fill the tube with oil.

You may have a mismatch between the sender on you 3.0 and the gauge in your 77, yielding false readings. Do you still have the 2.7 sender?

HotPorsche · 10-27-2003, 02:16 AM

If the trumpet is cold the tstat is not opening or getting hot enough with engine oil. If you have it apart I would definately replace it. Yes the tube will usually have oil in it.

Noel · 10-27-2003, 03:36 AM

Based on how quickly the oil temp goes up to 240, I would suspect the problem may be with the thermostat for the "On the engine" oil cooler.

RickKlem · 10-27-2003, 04:05 AM

Noel

That's what I was thinking also, but someone said in another post that the way to test that thermostat was to run the car to operating temps and then touch the on the car cooler. If the cooler is hot then the tstat was working allowing the oil to flow through. If it was cool to the touch then the t-stat was not allowing the oil to enter. Does this sound correct?

Rick

Tim Walsh · Tim Walsh's Garage

Rick
That's the way to test if your external thermostat is working or not. I would drop the thermostat is a bath of hot oil and see what it does. It should open up nicely. I would then check your oil temperature sender to see if it works with your guage. I'm willing to bet it's the wrong type.

RickKlem · 10-27-2003, 04:35 AM

Tim,

How can you you tell if it opens . I looked down into the orafices and could not really see anything. As for the sending unit, during the rebuild, I spent three days of research of which sender to use with my gauge. My gauge has been updated to the numeral type instead of the bar type. So I think its correct, but I have been wrong before (alot occording to the wife). I'm thinking about picking up a laser ,no touch, temp sensor from Sears today and check all of the areas in question. I will also double check the sender.

Is there an aftermarket t-stat that I can use for the external , like mocal.

Rick

Tim Walsh · Tim Walsh's Garage

I belive there is an aftermarket thermostat but I don't know for sure. I do know there is an aftermarket oil pressure guage.

I've never opened up the external thermostat but I do know you can see the internal thermostat opening. Just to make sure as well, have you set your timing to factory specs and you're not running lean?

RickKlem · 10-27-2003, 04:49 AM

Yes the timing has been set. I guess my confusion is why is the engine running so hot but the front oil cooler is cold. Because of this I fill like the external t-stat is not working.

Rick

RickKlem · 10-27-2003, 07:32 AM

I have some more questions,

Since I have the external thermostat off how can I test it before replacing it?

I have tried to remove the two very large caps (screws) from the external t-stat to clean and inspect every thing, but they are not coming of. What's the trick?

I just read on another post that if the internal t-stat is not working or is in backwards, that it wont allow the hot oil to reach the external t-stat . Is this correct? I thought the oil leaves the oil tank then to the external t-stat through the pipes and thrombone back to the engine and then through the internal t-stat then internal cooler. Is this incorrect?

Is it true that, if the internal t-stat is not working that the internal cooler will be cool to the touch?

Help me please.
Rick

RickKlem · 10-27-2003, 10:47 AM

Anyone?

HotPorsche · 03:43 PM

Hey Rick, My 77 was running hot, I checked the front loop and it was cold. I ordered a thermostat gut for the original housing (89.00) as opposed to 220.00 for complete thermostat wi housing. To get mine apart I had to remove the housing from the car and put it into a large vice. It was tight but finally came apart. I could tell mine was sticking so I replaced it without testing it. Put it back together and it now circulates thru the front loop (gets very hot). I do have a small oil leak where the oil line connects. I would put pipe dope on the connections before tighting if doing it over. PS when mine was not working the housing itself was hot (oil looping thru itself) but not to the front. Inotherwords the external thermostat never really shuts off, it just directs oil back to the engine when cold or to the front when hot. NOT POSITIVE ABOUT THIS!

Chuck Moreland · 03:11 PM

Quote:

Originally posted by RickKlem
I have some more questions,

Since I have the external thermostat off how can I test it before replacing it?

I have tried to remove the two very large caps (screws) from the external t-stat to clean and inspect every thing, but they are not coming of. What's the trick?

I just read on another post that if the internal t-stat is not working or is in backwards, that it wont allow the hot oil to reach the external t-stat . Is this correct? I thought the oil leaves the oil tank then to the external t-stat through the pipes and thrombone back to the engine and then through the internal t-stat then internal cooler. Is this incorrect?

Is it true that, if the internal t-stat is not working that the internal cooler will be cool to the touch?

Help me please.
Rick

As I said before, way back at the top of this thread, check for a mismatch between sender and dash mounted gauge. The sending unit on the 2.7 IS NOT THE SAME as your 3.0.

You are likely chasing a temperature problem that doesn't exist.

Do you have the old 2.7 sending unit? Put it in.

To answer your questions -

- To test the tstat, boil it. You should see movement of the piston inside.

- Sometime you can get the tstat cover off with big channel locks. Use penetrating oil too. Failing that, fabricate a tool by grinding a chunk of angle iron to fit the crescent, then use it as a lever.

- The internal tstat has nothing to do with the external tstat and will not affect its operation.

- If the internal tstat fails, the internal oil cooler will not be cool. It will still be warm. But if the tstat is working, and the engine is hot, the internal cooler will be finger-burning hot.