Overheating

[zcacogp]

Chaps,

Advice needed.

Long drive yesterday. London to Hereford and back, via some places on the way. Family funeral, but that's by-the-by.

On the way back, making good progress (110-120 arbitrary units) on the A-something the temperature warning light flickered on, and I noticed the gauge was high - just on the lower part of the "red" (by then illuminated) section. The car was running like a homesick angel and the oil pressure was fine - apart from the warning light I would have had no notion there was anything amiss. (My first thought was that the gauge temperature sensor had failed and the warning light was thus incorrect.)

Stopped, opened the bonnet, had a look. Cooling fans not on, engine seemed hot but not overly so (given the rate of progress.) No pressure under the radiator cap and the radiator (such as I could get my fingers too) was cold. I called a friend, and we jointly diagnosed a thermostat jammed closed, and I decided to head for home (another 75 miles) with care.

So, interior fans on full hot, opened the bonnet one click (better airflow) and limped along the M4 and across town at about 50mph. The temperature gauge remained in the low or mid red part most of the time, and dropped back to half-way up the scale on a couple of occasions. It did get hotter in town and was pinking if you laboured the engine (which I avoided studiously.)

This morning I ordered another thermostat, and have just taken the old one out of the car. I have reconnected everything, refilled the coolant and started it up, and it seems to run fine. I let it idle up to temperature, and it gets to the right temperature and stays there. Doesn't overheat. I have yet to drive it, but it idles fine and revs up fine.

Two concerns.

1. It seems to have used quite a lot of oil over the period of the day (bear in mind that the car did about 300 miles with no problems and 75 with a warning light on.) I checked the oil level at the weekend and it was fine, and I have just had to put another 500ml in to get it back up to where it should be. Should I worry about this?

2. The engine may sound different. There may be a fast rattle coming from the front of it - 'round the belts area. I am slightly paranoid, and I am not 100% convinced that this noise wasn't there before - I am just not sure.

So, questions.

- What damage am I likely to have done (or could have done) by running it with the temperature warning light on?
- Are those signs (oil use, funny noise) symptoms of that sort of damage?

I guess my worst fear is that I have jiggered something by getting it too hot, and it is now going to guzzle oil. However, the temperature gauge never got to the top of the scale and the oil pressure (even at idle) didn't drop below 1.5bar on the gauge, and wasn't below about 3 while driving along.

I'm off for a drive. Will report back.


Oli.

 

[zcacogp]

OK. Driven it. It drives fine. But is still overheating. And this is without a thermostat in the engine. So it's either the water pump no longer pumping (which, given the cam belt is still turning means that the impeller must have dropped off the end of the pump) or something is blocked somewhere. OR I didn't bleed it properly when I refilled it. But, given that the problem is the same as before I filled it, I suspect that isn't the problem. (However, having said that, where is the air vent screw on an S2?) Oli.

 

[TTM]

Warping the head would be the "worst" thing that springs to mind. Can you see white smoke (=burnt coolant) out of the exhaust. How does the exhaust smell?

 

[zcacogp]

TTM, Didn't look at the exhaust but there weren't plumes of white around, for sure. Nothing smells amiss. In fact, were it not for the light, I'd guess that nothing is amiss. Where is the coolant vent screw on an S2? Any ideas? Oli.

 

[TTM]

Same as on other models, it's on the aluminium elbow on top front of the head - there is a superb illustration in the owner's manual If the car is cold and if you have a friend around you may ask him to blow into the coolant tank until only coolant spills out of the elbow, by then the system should be bled before even having to reach the operating temp.

 

[alwigley]

Don't know if similar thing can happen on 944's but on the 1980's Vauxhall engines, the water pump used to be the collection point for lots of rusty crud as it was right down the bottom of the system and they used to 'fail' as a result. Have you tried flushing the system through thoroughly, and how clean was the coolant that came out when you changed the stat ? Spent many a happy hour under the bonnet of my old cavalier/astra etc. changing water pumps, and still have the scars to show it !

 

[zcacogp]

TTM, thanks. Found it. I was looking in the wrong place! Alwigley, no, the water pump is not the lowest point in the engine, and there wouldn't be much crud build-up there. I've just flushed the radiator, and it flushes clean and clear and easily. It still overheats when I drive it. And that's without a thermostat. And there IS a nasty noise from the engine. Seemingly from around the waterpump area ... I diagnose a duff waterpump. Damn. And I had a spare in my hands a month ago when I changed the belts on it, but decided not to fit the new unit as I thought the old one was OK! Bugger. Oli.

 

[TTM]

Sorry to hear this... Did you test the old thermostat in hot water to check if it really didn't open at 83°C? If it is functional then it will be quite clear there is something wrong elsewhere in the coolant flow.

 

[zcacogp]

No, but there is no difference in symptoms when the car is run without the thermostat in. I'm strongly of the opinion that it's a water pump failure. Oli.

 

[TTM]

Might some tiny foreign object have fallen into the coolant system and made its way to the impeller? When was the water pump last replaced?

 

[zcacogp]

Foreign object - possibly. I don't know. (I also don't know how big the clearance is between the impeller and the housing, and therefore how big the foreign object would need to be.) Just off to boil the waterpump. Quick, before the wife gets home ... Oli. ETA: Don't know when the waterpump was last replaced. It wasn't done at the last belts change (2000 miles ago), nor at the one before that (40,000 miles and 4 years ago). The guy who did it that time looked at the waterpump and said it was OK, but also said it wasn't the original one. So I can't be sure.

 

[TTM]

Original water pumps for the 104mm bore block (2.7, S2, 968) had a "2.7" stamped on the upper right area, visible slightly above belts covers, but for a couple of years Laso has made them all either with a "2.5" or no stamping at all...

 

[zcacogp]

Thanks. You sound like you know a bit about waterpumps. Is this: http://cgi.ebay.de/Porsche-944-S2-968-Wasserpumpe-Laso-N-E-U-/360276461651?pt=Autoteile_Zubeh%C3%B6r&hash=item53e2268853 ... for the S2 it claims to be for? Can you tell from the photo? BTW I have just put the thermostat in boiling water from the kettle. It opened smartly, and closed again when I held it under a running cold tap. I think it's OK. Oli.

 

[TTM]

This is clearly a water pump for a 2.7/S2/968, the "swirl" part on the back of the pump almost touching the impeller is machined to make room for the larger impeller. I believe Laso use only one type of mould these days, which forms the other type of water pump with the smaller impeller, perhaps the reason they all come now with the "2.5" stamping.

 

[simkin911]

Looks exactly like the waterpump I just didn't fit to my S2. I bought it via Berlyn but was sort of "talked out" of fitting it last week when the garage replaced the belts/tensioners etc. My water pump looked to be in v good nick and the garage suggested it was a waste of money replacing it so I thought I'd leave it to the next belt change. I just hope it doesn't now suffer a "premature" failure within the first few hundred or thousand miles following the belt change. On a positive front, at least if it's the water pump then you know it's not a hideously expensive issue to resolve? BTW, Oli, I want to say thanks for the PM you sent with details of the chain pad slippers and sorry I didn't instantly reply with thanks. Many thanks.

 

[zcacogp]

TTM, thanks. At the moment I am tossing up between buying that one from Germany, or a remanufactured one from Paragon in the states. The Paragon one is a chunk cheaper, but more expensive to get here and will take longer. I just wish I spoke better German so didn't struggle with the eMails quite as much! Steve, glad you got the message! I hope your waterpump experience is happier than mine, and in fairness there is no reason why it shouldn't be. My waterpump wasn't replaced about 42000 miles ago when the belts were last done as the garage looked at it and said it was OK. I suspect that I was just stretching my luck a little when I tried to re-use it again. Depends upon what you mean by "hideously expensive". Porsche want £466 for a waterpump. Fitting it involves removing all the belts and re-doing that job entirely, so whatever you paid to have the belts changed in the first place will have to be paid again (plus a bit more, as there's a few more parts to replace.) At £70/hr (what my local indie apparently charges) that's all going to work out quite pricey ... which is why I am trying to source a cheaper waterpump and will probably do the work myself. Oli.

 

[xenon]

Rats. []

 

[zcacogp]

No Xenon. We did have mice in the kitchen last month, but some well-placed traps did away with them. (The cat was a conspicuous failure in this regard; I watched one mouse chase aforementioned cat out of the cat flap on one occasion. Not impressive, particularly considering the mouse was wounded at the time and only running on 3 legs ... ) Haven't seen a rat for a while. I've ordered a new waterpump from Germany, which should be here in 2-3 days time. I'm in the process of stripping down the front of the engine (again!) and am currently debating how to get the big toothed pulley off the front of the crankshaft. I have removed the large nut, and the alternator and power steering belt pulleys, and the balance belt pulley is next. It seems to have a woodruff key in there, and is quite tight. A puller of some kind may be in order. Oli. P.S. Thanks for the kind sentiments Ian! []

 

[nick_968]

Oil I am interested to see what you think of the quality of the Laso unit, take a good look at the casting etc and the neck for the large coolant hose and compare the quality to the original as I have been thinking about getting one for when I change mine, but not sure on the quality against the factory pump.

 

[pauljmcnulty]

Glad to hear it's getting sorted. I suppose it's time to start nagging people to get the pump changed every second belt change. It's often been mentioned, but not really emphasised in the way I over-stress not pushing the belts past their 4-year maximum. Yours has done proper mileage, but is the pump life going to be down to time as well as miles? Is it 80K miles/8 years maximum?