SteveIX51

So after a fun weekend in which my computer hard drive, kitchen sink faucet, and shower head all spontaneously broke, I decided to drive the 944 to work this morning for a little serenity and enjoyment of the open road. Naturally, something went wrong there too, and I observed the following curious engine temperature behavior:

At idle, the temp steadily and continuously rises above the second mark on the dash gauge, and towards red. If I rev the engine a little, say 1500 RPM, the temp falls back to the middle of the acceptable operating range. The fall back down is quick, maybe a few seconds. Otherwise, operation seemed normal.

What seems clear is that coolant flow is being restricted somehow and idle engine speed is not sufficient to circulate it properly. The stagnating coolant in the engine block and near the temp sensor heats up quickly, which leads to the temp spike. The increased push from the higher engine speed then forces the coolant to circulate better, where the cooler coolant now flushes out the hotter coolant from the vicinity of the temp sensor, and temp returns to normal. (That's the only explanation I can think of that would let the temp fall back down so quickly.)

First instinct is naturally the water pump, maybe the bearings are starting to go and the engine is having a hard time driving the pump? (But no squealing noises, at least yet.) FWIW, the water pump is a rebuilt unit but only has 5k miles on it.

Any other thoughts or diagnoses? If it is the water pump about to seize, do you think I have long before that happens (I don't have any first hand experience with water pump failures, so I don't know)? Would that just occur suddenly, or would there be any warning? I'm hoping to be able to drive it home at least, which is about 10 mi away.

Thanks guys.

pnbell

Hey Steve,,,,

I had my water pump seize on me a few months ago... and well I noticed my coolant temp having the same strange fluctuations for weeks. (It would be hot; I would rev the engine and the temp would fall) Your thoughts seem correct: the pulley is getting harder to spin, reving the engine tightens the belt, and allows the belt to turn the pulley...

Eventually -after driving from Baltimore to DC- I pull up to a stop light, and watch my temp get real close to the Red; I shut the car down, get out, and notice coolant all over -from the overflow hose-...

After letting it cool down, and filling it with coolant I drove about a mile or two, and almost overheat again... After work I decide to try, and drive home... almost over heating every couple miles... I stop at a mechanic shop, and they quote me $300 for a tow to Baltimore... I borrowed some tools, and tore the thermostat out; thinking maybe it just wasn't opening... nope, didn't help...

Long Story short: I ended up driving all the way home; shutting the car down, and coasting when the temp got too hot. I did not wait till it was in the red though!!!

The 1 hour drive took me 6 hours... but I made it home. The next morning I remove the T-Belt cover to find a seized water pump pulley, and my timing belt with lots of missing rubber!!! I got lucky it didn't break. -It was a brand new belt as of a few months previous-
I did notice a slight chirping sound the day this happened. Must have been the bearing beginning to seize... no loud squealing. Most people would have not even noticed the chirping noise; it was so quiet.

I would say your water pump has not seized yet; but is starting too... 10 miles should be no problem based on my story... but if you can take the t-belt cover off, and look at the belt/try to spin the pulley it might be worth it.

When I removed my water pump I could barely spin the pulley using a pair of Vice Grips!! It was SIEZED!!

*If you need any assistance this afternoon let me know!! I am not too far from you; you should have all my contact info in the PM from last week*
-Pete

SteveIX51

Thanks Pete, that's quite a story. Sounds like the same problem and time for a new water pump. Oh joy.

And if you can make it from Baltimore back here after a few weeks of problems, I think I can make it home tonight. (Hopefully in under 6 hours.) Then I can put off dealing with it until over the weekend.

Thanks buddy.

mikey_audiogeek

My original water pump (plastic) impeller came loose on the pump shaft, gave similar symptoms to yours before it gave up the ghost. Common failure mode apparently.

Cheers,
Mike

I_am_imprezed

I guess thats possible but theres a few things you should look at. #1 are the radiator fans working? #2 is there a coolant leak? #3 is the Thermostat opening? #4 is the radiator clogged/air pocket? #5 Head gasket Leaking?

Also are you running straight water or 50/50? If you're running straight water you need to put coolant to lubricate the water pump. A water pump with that low miles should be working fine

Does the car run good with the heat on?

Mike951

Steve,

If you decide to replace the pump I have a brand new turbo-style(update) pump in the box for sale.

Thanks
Mike

SteveIX51

Yes

Not that I can see

It appears so, cooling system seems normal and is effective except at idle

Don't think so, cooling system has been working fine for two years now, and hasn't really been touched in that time frame. It seems unlikely that a clog, or especially an air pocket, would develop so suddenly and without any recent work being performed.

Not that I can tell.


Most likely culprit (and cheapest fix to start with) seems to be a defective water pump (maybe bearings, or perhaps as suggested above, impeller problem). I agree that it shouldn't break after only 5k miles, but it is rebuilt, and "shouldn't break" doesn't seem to go very far with these cars. I'll get under there more this weekend and see what's going on. She's resting safely at home for the moment.

Thanks for the help.

944Ross

Just a thought, if the weather has just turned cool there, and you've started using the heater in the morning, a big burp of air out of the heater core could have been released into the system.

odurandina

i replaced my H20 pump @ 114 k miles.


nothing like preventative maintanence.

pnbell

Hey Steve, I will be around this weekend if you want a hand -or someone to stand around, make comments, and lift the car off you,,, if it falls off the jack stands...

Let me know.

-Peter

Darwantae951

What brand of rebuilt pump did you use?

kingston944

If the belt is to loose then not enough pressure against the water pump pulley to keep it flowing properly I had that problem before. I keep a good eye on belt tension now.