Still running hot - Please, help a brother out!

1990 Limited - Operating temp 235 degrees... WTF?

It is the fully pressurized system... with no radiator cap... just the pressurized puke tank.

So far I have replaced the puke tank, the water pump, the thermostat (then reinstalled the old one), flushed the system (myself) and put in new coolant. My operating temp is still around 235 (as the gauge reads).

Despite having a 195 degree thermostat, I can see the temp gauge needle rise to about 215, then dip when the thermostat opens (this is the same with two separate thermostats, so I ruled out a bad thermostat).
Even with a 20 degree margin of error on the gauge, I'm still running hot.

The only strange thing I can find is that while running at 235 degrees I can squeeze the hose that connects the block (just off the thermostat) to the top (intake) of the radiator and it will not be full of fluid... it won't be tight with pressure... it feels mostly empty. Also, the same hose is hotter near the thermostat than near the radiator. Somehow, I am not getting proper flow through in the coolling sysytem.

I have tried disconnecting that hose at the block, filling it with fluid, then quickly re-attaching it... still running hot.

Please, for the love of Pete, help a brother out.

Thanks.
E5B

Sounds like air--you need to burp it. The closed cooling systems are notorious for trapped air.

Things to do:

Whenever installling a new thermostat you need to drill a couple holes in the flange of the thermostat. They should be put in the flange where they won't be blocked off by the mounting surfaces. Position the thermostat holes so they are at 12 and 6 o'clock.

Topping up the system with the upper rad hose is good. Now you need to park it nose-down and remove the temperature gauge sender from DS rear of the head to let any trapped air escape while you keep adding coolant to the pressure bottle. Remember, you don't want the bottle to be more than 1/2 full when cold. An alternative to pulling the gauge sender is to use a later model thermostat housing, the kind with the sender outlet, and put a radiator drain petcock in the sensor hole, that allows you to open the petcock instead of pulling the sender, which can be a bit bothersome when the engine is hot.

Anyway, once you get it burped things should settle down. Post back and let us know how it comes out for you.

Brilliant! Many, many thanks.

I'll report when I've done it.

Thanks again.

Like so:

This is a 92 t-stat housing ($2.00 at JY) in my 90. Like Joe says, take out the sensor , put in a petcock. I don't open it often but I know the air's out when I do.



I didn't read anything about the fans, either one. Is the e-fan working? How old is the fan clutch?

Is the water pump (and belt routing) going the right way?

mine never would cool unless moving down the road. no matter what i did and with no air in the system. changed to the "open" system no more probs. i even went as low as 160 degree tstat and still had probs

X2 on the e-fan.

As Joe said, air in the system. If the hoses aren't pressurized significantly and full of fluid something is amiss. I have never had to drill thermostats, relying instead on the factory design. My usual bleeder is an Airlift cooling system vacuum filler but hills, filling hoses, loosening temp sensors and so on works too.

Thanks for the great replies. You were spot-on, Joe... air bubble in the system.
The solution:
First, I partially drained the system, removed the thermostat and drilled two small holes in the flange, one at the 12 O'clock pos and one at the 6 o'clock pos, then reinstalled it.
Next I parked nose-down, let it cool, and removed the temp gauge sender on the DS rear of the block. I refilled the pressure bottle until fluid came out, then put the sender back in. Topped off the bottle, closed everything up and drove it around the block about 15 times. Operating temp = 210. I'll take it!
If it happens again, I think I'm going to go with the modified housing... much more convenient, I suspect.
BTW, I have the e-fan hard-wired to a toggle switch under the dash and it works fine. The clutch fan is also good to go.

Thanks again, Fellas.
Take 'er easy.
E5B

Glad you got it!

glad you did too. i also ran 2 elec fans and it helped a lil. if you need to get it a lil lower