Got Me a Porsha

To the 944/951 folks that have replaced water pumps, has anybody seen a failure other than the typical bearing noise, shaft seal (leak), or pulley slip? I am suspecting an impeller issue at this point, but I have never seen nor heard of this happening.

This is the second AZ summer on my rebuild, and all of a sudden the car loves to run at the top white mark. All the obvious has been replaced, gauges serviced, grounds replaced, system bled 42 times, low temp stat & fan switches, griffin radiator...and we are completely out of ideas. I have even tried several different thermostats (down to 10 minute job!), no thermostat, even drilled holes in it, with the same results. Water pump appeared to be a new replacement when engine was torn down. I have marked the pulley and shaft but see no slippage.

The car runs "in the middle" in traffic or idling, with the a/c on, at 110 degrees outside. At highway speed, or under boost, it climbs immediately to the top of the range and stays there, until stopping...then cools down.

I suspect a water flow issue at this point. Any ideas?

bjzorn

Umm it should go the other way when on the Highway as there is more air flow, it should towards the bottom. I hever heard of a impleller failure. Do you have any coolant loss at all? fast or slow? Do you have a bearing noise in the front of the motor?

Got Me a Porsha

Exactly! You see my confusion here. No coolant loss, no bearing noise. Belt covers are now off so I can keep an eye on things. Belts are new, and been retensioned. Im puzzled

bjzorn

Just found out on clarks garage that the impeller can seperate from the shaft, how ever you should be experience coolat loss if this is happening

Got Me a Porsha

I suspect slippage...at least. Would like to know if anyone has seen that.

Thanks for the info!

sillbeer

Im curious too..is it possible you have a bad gauge sender? I think mine is reading high...Ive heard of bad grounds causing all kinds of problems

M758

Did you ever trace this issue?

I started driving my 951 after a LONG break and it is doing something similar

Mornings when its cool (85-90F) the car runs down the lower end of the normal range. This is A/C on or A/C off. It will creep up with out the A/C on, but the fans kick in and it cools down. In the afternoons on way home with 105F temps it runs fine at idle even sitting in traffic, but climbs even under light acceleration. It then stays at the high white mark for the rest of the drive.

I have bleed the system and know it is holding pressure. I am thinking it may be weak T-stat not allowing full flow, but I have not checked.

Rip It

Radiator fans moving air in the correct direction, towards the engine?

austin944

Is there a reason not to suspect a blown head gasket?

Got Me a Porsha

Joe-

No solution to the problem yet, although, the problem has progressed to the point of making the car a nice addition to Jeremy's yard, amongst the pink flamingos and garden gnomes.

We pulled the motor Saturday morning, and started disassembly. The head gasket was in excellent shape. Hopefully we will remove the water pump this week and inspect. I fully suspect the wp at this point.

Before parking the car, it did exactly as you describe. It will idle all day while 110 outside, a/c on or off, bumper 2 bumper traffic, and not reach halfway on the gauge. But, two miles at highway speed take it right over the top mark, near red. Basically its load related.

I tried a new stat with no change, and no stat, making it slightly worse. Fans are verified correct. System bled 58 times.

I will update as we dig deeper.

M758

Kevin, Did your car run cool in the morning hours? On my drive to work at 5:45am to 6:30am the engine temps were nice and cool. That leads me to believe the waterpump is turning, but maybe the T-stat is not opening enough to flow water in high heat under load.

944S2IFISH2

Got Me a Porsha, my '90 S2 had a waterpump fail with a slipping impeller - it does happen! The impeller spun free on the shaft (Like it was on bearings). There was no leakage and no "strange" noises. I thought I had a stuck thermostat, and after f##king around for hours trying to pull the circlip and change the T-stat in-place, I pulled the water pump and was suprised to find the impeller just spinning on the shaft. FWIW the pump was original with approx 65,000 miles on it. YMMV...

Jeremy Himsel

Joe what's you're describing is exactly what Marlow's 89 951 did. We changed the stat and it got a bit better but ultimatly it took a new radiator to get it running cool. Visually the radiator was perfect but 20 years of build-up got the best of it.

My car was the exact same way. As soon as I put it under load you could see the temp gauge rise with the RPM's. When I came to a stop at a light it would drop down and start the process over. By the end of my commute, it was heat soaked enough that it was happening in the upper range of the gauge. A new radiator resolved everything.

Jeremy Himsel

Umm, those aren't garden Gnomes. That's AZBanks playing in my grass.

M758

Interesting,
My car has a relativly new radiator (installed 15k miles ago). I am thinking now I will pull the T-stat and test it vs a couple spares I have. Then if it tests ok compared to new. Then pull the water pump. I don't know how old the waterpump is on this car. I have had it for 10 years and I don't remember doing the pump on this one.