Over heating issue.

[massive]

Took my 84 944 out for a 30-40 mile trip on the motorway to pick some people up from the airport but failed to reach my destination due to unexpected temp rise.

At the beginning of my journey the car started as normal and proceeded to warm up as normal for the first 15-20 minutes on the motorway. As I was driving up a long but steady incline I noticed the temp gauge rise slightly above the half-way mark where it normal sits when doing 70mph. On the decent the temp gauge dropped to below the half-way mark.

5 mins further down the road I glanced at the temp gauge again and the needle was all the way up at the max, so I quickly pulled over, popped the hood, there were no signs of steam, but there was a kind of squealing noise (not as loud as a fan belt squeal, more like a mouse squealing noise). I turned off the car straight away and called my breakdown company who flat-bedded the car to the nearest service station where they checked it over.

On inspection they found the expansion bottle was empty, they released the coolant bleed valve and topped up the water with about 2.5l of water until it flowed from the valve.

They then checked the oil on the dipstick which appeared normal with no milkyness. They also checked the oil filler tube, again no signs of milkshake.

They then pressure tested the coolant system and found that there were no leaks as it held a steady pressure.

By this point the engine was cool so we started the car and let it tick over to build temperature again.

It took about 15 minutes for the car to get up to normal temperature, during this point the temp gauge rose as normal and steadied at the normal half-way point. The mechanic was also checking the engine, hose and rad temps with a infra-red thermometer, nothing out of the ordinary. The engine seemed to be ticking over fine, no squealing either. The rad fan also switched on when it needed to as well. We also checked that hot air was passing into the cabin through the heater matrix.

The mechanic was about to conclude that it was probably just air in the system from the service that had been done 2 months prior. Then the squealing started again, I checked the temp gauge and the needle had risen to the 3 quarter mark, at this point water started backing out of the expansion cap. So we turned off the engine. He checked the temps of the radiator and found the top half to be normal whilst the bottom was cooler than expected.

At this point he said the car was not drivable and what motor mechanics do I want it taken to as he thought the coolant system was likely blocked and needed flushing. He also thought it could be the head gasket, but thought the blockage was more likely.

Has anyone had a similar problem or could offer any suggestions, the car is now at the mechanics waiting to be inspected.

Just another piece of info is that I had the thermostat replaced about 2 years ago for a new one from porsche, just rule out something else possibly.

Hope someone can offer advice.

Best regards

[CHICKS]

Was the belt cover pulled to see if the pump was seized or maybe locking up somehow?

[massive]

Originally Posted by CHICKS

Was the belt cover pulled to see if the pump was seized or maybe locking up somehow?

Nope they didn't do that

[CHICKS]

I'd pull the upper cover and run the same test to see where the squeal was coming from. After checking belt condition of course.

[sausagehacker]

water started backing out of the expansion cap

Was it coming out from the cap, or from the overflow at the back of the tank?

If the system holds pressure, and the water is coming out of the cap-to-tank interface, the cap is clearly not allowing the system to hold pressure. This leads to the temp sensor (not the EFI one, the actual sensor for the gauge) to read high temps because of the latent heat of steam (which wouldn't be there if the system was pressurized).

If it's coming out of the overflow, the cap is probably fine, and you're likely looking at something wor$e like a WP or blocked radiator passage.

[massive]

Originally Posted by sausagehacker

Was it coming out from the cap, or from the overflow at the back of the tank?

If the system holds pressure, and the water is coming out of the cap-to-tank interface, the cap is clearly not allowing the system to hold pressure. This leads to the temp sensor (not the EFI one, the actual sensor for the gauge) to read high temps because of the latent heat of steam (which wouldn't be there if the system was pressurized).

If it's coming out of the overflow, the cap is probably fine, and you're likely looking at something wor$e like a WP or blocked radiator passage.

Yeah sorry, actually your right it was the overflow, been such a crazy day.

Sent from my GT-I9300 using Tapatalk

[massive]

Update:

Things we've checked/changed so far:

1. Checked oil filler and dipstick for milky oil = Oil looks fine and level was in the middle between min and max.
2. Pressure tested coolant system = No leaks found
3. Changed old thermostat (2 years old) for a brand new one from Porsche = Same problem with coolant backing out of expansion tank overflow.
4. Removed the alternator belt and power steering belt = Squeaking still happens


Are there any other things I should check that will confirm or eliminate some possibilities?


Also does anyone know a good independent Porsche mechanic in the Kent area (United Kingdom) ?

Thanks in advance.

[kdjones2000]

Sounds to me like your water pump bearing is dying, causing high turning resistance and locking up/squealing when hot.

Take the covers off and test it...

Good luck, Keith

[sausagehacker]

Agreed, water pump. I highly recommend that you do not start the engine again until a new WP is in - if it seizes, it can wreck the timing belt.

[CHICKS]

Water pump. Was the pulley spun when t-stat was replaced? How did it feel?Again, How does the belt look? Any belt dust?

[fiat22turbo]

You could still have a blown headgasket. Headgaskets can fail and not cause oil/water mixing.

Another thing to check when looking for over heating, is whether the radiator has cold spots as it should be fairly evenly warm across the surface, cold spots indicate that is is plugged.

I would agree that the squeaking is a sign that your water pump is likely on its way out. Time to do a FOES and see if that helps.

While you're doing that, you can have a coolant sample sent out and tested for combustion chamber contamination to help indicate whether you have a leaking headgasket.

Once it is all back together, I'd make sure your hoses are in good shape and that the lower belly pan is in place as it helps with aerodynamics at speed and helps with cooling at highway speeds. Many people toss them and don't put them back in place.

[massive]

UPDATE:

Appears to be a very small amount of oil in the coolant, I had the seals done on the oil cooler 2 years ago, so it's looking likely it's head gasket?

Will check the spark plugs tomorrow for steam cleaned look.

[guru944]

massive:

Time for Upgrades.....Cometic MLS, Headwork, DME, MAF Go for it...

Head gasket at least.... Later...

[Gordon Rankin]

And the verdict is?? What has happened?

[massive]

Yes, finally got the problem sorted about 2 weeks ago and now my 944 is back on the road.

The problem was a seized water pump, looking back through the history of the car I couldn't ever see it having been replaced at any stage, so I guess at 140,000 miles that's not bad going.

We replaced the water pump and belts and everything is back to normal thankfully. Need to get my alternator serviced now as the bearing feels like it's seen better days.