My sons bought a 1984 944 NA w/ AC, and I've been trying to help them get it back on the road.

When purchased, it had a clutch that was whacking the limp home tabs; they dove in and replaced that. After, a non-start condition was traced to the flywheel sensors. Easy in comparison to the clutch job.

Now, when we run the car, it dumps all (well, most) of the coolant on the ground from the overflow hose upon shutdown. We've driven it in the neighborhood for 30 mins, no problem. We've idled in the driveway until the fans and thermostat have cycled several times, no problem.

So: what? What to diagnose or replace next? Help is needed!

So far:
* Installed new OEM pressure cap on expansion tank
* Tried every coolant bleed technique on the internet and in the manual.
* Used a pressure tester to discover loose hose clamps; tightened them. All hoses seem new (i.e. not 35 years old).
* PO replaced water pump & thermostat.
* Replaced a dodgy radiator drain plug (it's now completely dry)
* Discovered the PO had several of the relays in the wrong spots; fixed that to gain back proper fan operation including when AC on, and gained our heater blower motor back.
* Checked compression -- it's 140-140-140-140 across all cylinders
* Used a block tester to test for exhaust in the coolant. Fluid stayed blue and/or the bulb stayed compressed, so doesn't look like head gasket problem.

The only remaining symptom, other than the "big one" (all coolant dumps out immediately on shutdown) is that when we use the pressure tester to pressurize the system to 10psi, we get a drip every 2 seconds from the driver side of the radiator that could be the junction between the radiator and the plastic side -- although, as you know, you can only see about 1" of the radiator from the front because it's behind the AC condenser.

We've tried everything, no? What next?
Buying a new radiator is a big ticket item if we're wrong about the problem.

 

Only things that comes to mind.

1) retest pressure closer to 16psi
2) make sure you coolant mixture is correct, too much water vs antifreeze will boil out. Antifreeze has a higher boiling point.
3) start car and make sure there aren’t air bubbles in expansion tank. If so could be trapped air or leaking headgasket will pressurize the tank. Remeber hear messes with gaskets and metal so make not show it’s self on a standard compression check.
4) Double check thermostat orientation and install.

 

For some reason if you still suspect the radiator, you can try cleaning it using Blue Dawn detergant and/or radiator flush. I would take it off if you try the Dawn as you want it all out. Also clean the outside well as dirt/bugs ect can effect the cooling properties (pressure washer is good for this, dont damage the fins)

 

@CyCloNe! thanks for the response....

We didn't see air bubbles in the expansion tank during operation; we just get bubbles & overflow on shutdown.

I think we're in the market for a new radiator, especially if the recommendation is to test @ 16psi. All-aluminum is tempting, although 12-15% of what we paid for the whole car.

Hoping it's not the head gasket, although we ran the block test w/ the colored liquid and it stayed blue.

Thermostat was installed by the PO, but if we're going to drain everything & yank the radiator, that would be the time to access and check. We're pretty sure the water pump is the updated one -- we have a recent receipt for the kit that has the "don't let the belt hit itself" piece although not for the water pump itself.

 

pressure test the cap also. if the system can't hold pressure, it will allow the coolant to boil at a point determined by the coolant mixture. .

 

Very good point as well... I always suggest start with the cheaper things first. Most of the time it’s a simple solution and some times it’s the big stuff but best to start small.