[AT] HELP I'm stumped. truck problems, overheating

charlie hill charliehill at embarqmail.com
Tue Sep 1 16:21:53 PDT 2015


Thanks Steve.  I think I have the problem solved now except for the
weeping on the t-stat housing flange and that is my fault.  I changed
it in a hurry.  The flange looked clean and I didn't check to make sure.
I'll fix it when I replace the hoses in a few days and I'll check for the
air bleed hole in the thermostat.  If it's not there I'll drill one.  I used
to do that to every thermostat I put in anyway but with these computer
engines being so sensitive to everything I didn't want to do it.  I really
don't know if the new one I bought had a hole in it or not.

Charlie

-----Original Message----- 
From: Steve W.
Sent: Tuesday, September 01, 2015 5:54 PM
To: Antique tractor email discussion group
Subject: Re: [AT] HELP I'm stumped. truck problems, overheating

charlie hill wrote:
> Thanks Steve, that makes sense.
>
> If there is a bleed point on my truck I haven't seen it but I think I
> have the problem solved.  I've given it every opportunity to heat up
> for about 200 miles and some sitting and idling with the AC on in 90
> deg. temps and the temp is staying just below the 200 deg. mark just
> like it always has until this recent t-stat problem. I'm going to go
> ahead and flush the system, replace the hoses and fix that minor
> weeping on the t-stat housing in the next few days.
>
> One thing I found interesting on the old thermostat (which was the
> factory original piece) is that it has a small bypass hole in it with
> a little metal plug that acts like a leaky check valve but apparently
> it wasn't enough to prevent my problem.  Funny thing is, when I took
> that t-stat out and put it in a pot of water and heated it up, it
> opened just like it was supposed to and when I turned the heat off it
> closed just like it should too.  Strange.
>
> Charlie

GM recommends to vacuum fill the trucks. BUT your bleed point is the
surge tank cap.

That little hole was the air bleed in the thermostat. If the replacement
didn't have one then it is what caused the issue you had. I drill any
new thermostat in vehicles that have air issues.

The wifes Liberty with the 3.7 is one that will make you look for the
thermostat. It's in the housing attached to the block and the lower
radiator hose!

I would pressure test the system. Almost sounds like it developed an
air/steam pocket which displaced coolant. That let it heat up and cause
problems. It's possible that you have a minor leak that only shows up
under vacuum as well. Had a Dodge in a while back that was losing
coolant only when the temperature dropped. It had a small crack in the
radiator tank that would seal under pressure or expansion from heat.
Only showed up when the engine was cold and the outside temperature
dropped rapidly. Found it while testing the system. Owner liked that I
found the problem, didn't like the cost of the radiator.....

If you don't vacuum fill-

1- Fill the system through the surge tank opening.
2- Pre-mix a 50 to 60 percent solution of DEX-COOL and clean. drinkable
water.
3- Slowly add the pre-mixed solution to the surge tank until the level
is slightly above the surge tank split line.
4- Start the engine.
5- Idle the engine for 1 minute.
6- Loosely install the surge tank cap. Do not allow the system to build
up pressure.
7- Cycle the engine from idle to 3000 RPM in 30 second intervals until
the engine coolant reaches 99°C (210°F) and the thermostat opens.
8- Shut off the engine.
9- Remove the surge tank cap.
10- Start the engine.
11- Idle the engine for 1 minute. Fill the surge tank to 1/2 inch above
the COLD FULL mark on the surge tank.
12- Install the radiator surge tank cap.
13- Cycle the RPM. Idle the engine to 3000 in 30 second intervals until
the engine coolant reaches 99°C (210°F).
14- Shut off the engine.
15- Top off the coolant, as necessary, to 1/2 inch above FULL COLD mark
on the surge tank.


-- 
Steve W.

_______________________________________________
AT mailing list
http://www.antique-tractor.com/mailman/listinfo/at 




More information about the AT mailing list