gratian

Dear friends,

I have overheating problems...one week since first time change the fan switch with 69C new one, change the thermostat with 85C one, but still not good.
Now, when the needle touch the middle white line, the fan starts to run, but the lower hose is still cold, so no water flow. The needle remains at middle and the fan runs continuous witch is not good...Water raise about one inch in reservoir...
I bleed maybe 20 times.
I thing the water pump impeler is bad, worn, loose from the shaft...How can i see the water pump impeler condition without get it out? The outside pulley is ok, no strange sounds, no leeking, turn with the belt speed...
Is there any chance to touch the impeler with the finger through thermostat hole, or to insert an endoscope camera and see the impeler?
Or you guys can sugest something else?

harveyf

If your goal is to check the impeller, pull the top hose loose and run the engine briefly. It will certainly make a mess but will prove the pump is working or not.

The bottom hose being cold is your main clue. The thermostat has to open to get water through the bottom hose. There is no immediate harm to running the car with no thermostat, if you want to try that as a test. Or pull the thermostat and confirm it opens by placing in boiling water.

And it is possible that your radiator is massively clogged.

This may help: https://newhillgarage.com/2018/02/04...tem-explained/

BTW it always help to mention the year and model of your car.

harveyf

Less messy but still a valid check is to remove the high point bleed screw and crank and/or run the engine for a second.

gratian

Thank you!

So, if i pull the top hose, but the engine is cold, thermostat is closed (pump is running in bypass mode) water must come out when engine is started? Or the thermostat must be open to make the flow...
And how to check the radiator? the water is running nice on low exit now...
924S 1987, i think "new style" pump...
Check 20 pictures of it and i think i can see the impeler moving with a 6mm endoscope camera and slowly turning the pulley..i have to try...

harveyf

Yes. Engine is cold. Thermostat is closed. But if you disconnect one end of the top hose and just crank the engine on the starter, if the pump is working it will shoot water out the end of the hose. This only proves that the impeller is not totally stuck or the shaft broken. And like I said before, if you have a high point bleed screw, you can leave the screw out and crank the engine. You should have water coming out the hole. How fast I'm not sure but if it barely comes out, then something is wrong.

You put in a new thermostat? New is new but if your lower hose is cold you might try 2 things. 1) take the thermostat out and test it in boiling water, to make sure it opens 2) take the thermostat out, connect the hoses back up, and run the car. If the lower hose gets hot, then the radiator is working. If it stays cold, then the radiator must be really clogged.

gratian

Not a single drop came out....i have to remove the pump.
Please tell me what (part number) pump to buy? there is an "updated" model? What are the differences?

gratian

If i remember 15 years ago when i replace the pump, i manage to get it out without unscrew crankshaft bolt...maybe i cut somewere the plastic cover?
Some tips here...

Arominus

Don't do that, its a hack and more work than just pulling the bolt and crank pulley. Get a flywheel lock and you'll have no issues popping that bolt loose. Don't forget to replace the o-ring behind the small cog on the crank, not doing that can result in no oilpump drive after re-assembly.

gratian

"not doing that can result in no oilpump drive after re-assembly."

Thats why i have to bypass that. I still remember i "worked"my back cover many years ago (i never loose that bolt, but change one time the water pump) so i will try again to slide it over that pulley...

ClassJ

This sounds like a bleeding issue. Did the thermostat have a air relief hole? Was it oriented up?

Bleeder open with slight dribble while filling? Nose jacked up? Rad cap open?

The 944 requires “coaxing” after initial fill to get the thermostat open. You need to be careful not to overheat the car and be patient. When it opens the coolant level drops and you can finish filling system.

gratian

I bleed maybe 20 times now...when engine is running, with the air relief screw off, i get no water movement there...impeller is stucked/ loose from the shaft inside the pump...

gratian

At some point, fan will start to run and even the thermostat will open due to direct heating, but temperature will stay in the middle with the fan continuous running (not good in the summer)

gratian

I change the water pump....the old one was in good shape...still running hot...
Without thermostat, when dash needle is in middle position, the fan start to run and remain that way all day long, even when i drive the car, but needle goes down to first white line so real temp is under 80C...(yes, the switch is a new, low temp 80 to 70 *C)
The big problem is when i stop the engine, the fan will run for about 10 minutes (so will drain the battery on low term)
Maybe with thermostat on car all things will change?

I change the pump with crank bolt on engine...the "new style" plastic back cover is easy to remove.
Water will not spill on that air relief bolt when the pump is good....so you cannot see the internal impeller state by observing that...

Oh and those water pump screws...i was young but not stupid...many years ago I use antisize paste...so unscrew them like working on a brand new car...thanks me...

Christopher Zach

Fans are supposed to run for a bit after engine off. Cools down the radiator. Note, if you're going bonkers about passing the first line in the summer you are chasing a non-problem. Mine goes to the second bar with the AC on, and that's about it. This is not abnormal.

gratian

Still boil watter after a while but now also greassy brown color mix comes out with the water. Could be the an water/oil cooler valve o-ring of headgasket?
Also a problematic heat exchanger can cause overheating?
Engine oil looks ok, no contamination.