New waterpump and thermostat - now big header tank pressure? (And higher temp and more fans)

[Sandspider]

Hi all

Got my car back from my indie today having had the belts, waterpump and rocker cover gasket all replaced - fixing a list of niggles. The garage bloke said it was great - he'd bled it thoroughly, run it for an hour and not a drop of oil or coolant had leaked.

All good thinks me, so I drive it to see a friend, stop for a couple of hours then head home with a couple of miles of spirited driving along the way. But as I get near home, I notice that the temp gauge is much higher than usual - near the top 3rd, where normally it's mid way up the bottom third. Took it the rest of the way home gently (temp gauge stayed high), and switched off. The fans were running, which normally just happens if I'm in creeping traffic or similar. They stopped after a minute or so, so I bled the system again - 30 seconds of steam then water. Thought I'd check the coolant level (the indie said it might need a top up), so I loosened the expansion tank cap only to have a trickle of pink coolant escaping. Before I could tighten it up again, the top of the expansion tank leapt off, and about 2 litres of super high pressure coolant went everywhere. Managed to get the cap back on, then the cooling fans started up again. Bugger. I topped the coolant level back up again, let it cool for half an hour or so, then took it for another drive.

Temp rose quickly again, and the fans kicked in while I was moving to bring it back down to just above the bottom 3rd of the temp gauge. Got it back home, started to loosen the reservoir cap, and saw the pink coolant moving up the tank so tightened it up again sharpish. I opened the bleed screw again, and only steam came out - hardly any water at all. It steamed for two or three minutes, then I tightened it up again, and opened the expansion tank - all normal there now, coolant nicely mixed and stable.

So, my question is (whoops, bit long winded!) do I just need to bleed the car more, or is there a problem? (I read on here that a faulty thermostat can cause header tank pressure - the thermostat was replaced today). I could take it back to the garage of course, but I need to drive to London tomorrow and would rather not have to leave it at the garage again. I could also hear a strange rythmic rubbing noise from the front of the engine when stationary, and the engine sounded a bit harsher than before the work was done (or so I thought - can't be sure now and may be paranoid!).

Thoughts please?

Many thanks.

 

[robwright]

Normal temperature for our cars is actually around horizontal to 2/3 up the gauge. Most 944s haven't ever had their thermostats changed so run too cold. It is never adviseable to remove expansion tank cap when the car is hot for the reason you have discovered. Worry when your temperature goes above the top third and your warning light comes on. And yes your car will probably need bleeding again now.

 

[Sandspider]

ORIGINAL: robwright Normal temperature for our cars is actually around horizontal to 2/3 up the gauge. Most 944s haven't ever had their thermostats changed so run too cold.

Cheers Rob. I had read that, but my car still seems to be running too hot - hence the fans kicking in under normal gentle driving.

It is never adviseable to remove expansion tank cap when the car is hot for the reason you have discovered. Worry when your temperature goes above the top third and your warning light comes on. And yes your car will probably need bleeding again now.

Previously, after bleeding the car I've released the final pressure from the expansion tank by loosening the cap to the first position, where it just lets the pressure out gently, then I can top up the expansion tank as necessary. I will bleed the car again, but will that cure the temp and pressure problem, or do I need to go back to the garage?

 

[robwright]

How do you know they were kicking in whist driving unless you were driving very slow and hence not getting proper cooling? I hardly ever notice mine kicking in apart from when I am conciously looking for it when sat in traffic. I am just playing devil's advocate here mate. If in doubt in ther first instance after having work done and if you are not happy I would at least call your indie. A lot are surprised how how the car will run after changing thermostat. When I pull off the A1 and queue on the off road for just a couple of mins on the way home it is not un usual for the fans to kick in and then to be running when I switch the car off.

 

[Sandspider]

Well, I drove in the normal way, then when I slowed down to pull onto my drive (so having been driving at 30 - 40mph, no traffic) the fans were already on. Fair point though - I doubt the thermostat has ever been replaced before, so it may well act differently to the (probably) 26 year old one that came off there! I will call my indie tomorrow morning, but I'm hoping I don't have to go back there and that I can take the car on a reasonable journey tomorrow night...

 

[jefft]

This sounds a familiar story from my posts back last year. My problem was down to a new 87deg thermostat not opening correctly and resolved eventually by changing the new thermostat for a genuine Porsche 83deg one. I was also concerned about how noisy the new belts were, but after some reassurance from a fellow 944 owner I am pleased to say that he was right and things are a lot quiter now.

 

[robwright]

Fair point about the temperature setting of the thermostat Jeff. Worth checkng that with the indie Giles. Be gratefull you don't have 2 thermostats to deal with like me []

 

[Sandspider]

I will check that, thanks chaps. My indie definitely said it was a new Porsche one - £31 worth! Just topped it up and drove it again, and the temperature seemed better - no more than halfway up the gauge this time. The fans weren't on when I got back, but they kicked in shortly after I switched off. More water and less air from the bleed screw this time, but still plenty of pressure in the header tank. There's also an odd rubbery rubbing noise from the belt area at idle - about one "rub" per second. Goes away when revved, or at least, I can't hear it any more. [8|] One more thing to mention to my indie tomorrow. Why didn't I get a Celica?! (Joke...) [:-]

 

[robwright]

Best thing is a pressure bleed. You can do it by mouth or with my new patented pressure bleeding header tank cap. Available by postage.

 

[Eldavo]

I had the Mrs inform me this morning that the fans was running on the car and probably had been overnight. Luckily it sits in the garage on a battery conditioner so battery was fine. Unplugged the fan temporarily and looked around for prices on a new radiator fan thermostat switch and was quite suprised at the variation: OPC - £24.44 (Before PCGB discount) ECP - £15 GSF - £5.65 Guess where I'll be going then!

 

[Sandspider]

Thanks for the offer, Rob, but I think I'll just drop it back to my garage. Just spoke to them. He seems to think it's all normal, and if I'd just left it to today to top up the expansion tank rather than doing it last night, all the pressure would have forced the last air out of the system overnight. By doing it too early, I let water out and let air back into the system again. (Which kind of makes sense I suppose - though I'm not quite sure how leaving a sealed pressurised system under pressure would expel air from it). He's said he'll bleed it again for me today (2 hours work apparently)... He also said my thermostat opens between 80 and 95C, and is the "normal Porsche" one.

 

[DavidL]

It doesn't sound that normal to me! When I've had cars back with work to the cooling system I don't expect to have to play with it myself. I think I'd politely ask them to fix it (again) Noticed you're in Bristol. Wasn't somewhere in St Pauls was it?

 

[jasonp]

hiya giles, can see your in a bit of a predicament re your specialist, but after having the amount of work carried out and your car not running "true" i would take it back to the specialist asap,you should not have to be working on your car after just getting her back, this is down to the specialist to sort out, i am off to my specialist for the slightest thing as i know bugger all about spannering and topping up oil and water is my limit, the garage is responsible for making your car right, i would put the ball back in there court, best of luck anyway and keep us posted on your results, regards jason p

 

[Sandspider]

Thanks guys. I took it back in this morning, and they gave it a quick re-bleed & checked the fans came on when they should - took about 20 minutes. I won't drive it to London tonight (gives me an excuse to get the girlfriend to come to me instead!) but I'll leave it alone this time and just keep an eye on water level and temperature. It turns out that changing thermostat, water pump and belts at the same time makes quite a difference to the car (correcting it from the slightly off temps and pressures I'm used to), as well as giving me a chance to be paranoid! [&:] And DavidL, yes, the garage is in St Pauls. Do you know them? I have mixed opinions...

 

[DavidL]

I'll send you an email tonight. David

 

[Mike_Pollock]

ORIGINAL: Eldavo I had the Mrs inform me this morning that the fans was running on the car and probably had been overnight. Luckily it sits in the garage on a battery conditioner so battery was fine. Unplugged the fan temporarily and looked around for prices on a new radiator fan thermostat switch and was quite suprised at the variation: OPC - £24.44 (Before PCGB discount) ECP - £15 GSF - £5.65 Guess where I'll be going then!

Just replaced the thermoswitch on my 2.7 and I think the GSF one you quote there is the wrong one. 931VG0220 RADIATOR THERMO SWITCH 944 2.7 11/88>08/89 3 Pin +AC 9.25 I think this it the correct one and price is ex-VAT and not neccesarily the one available in you local GSF - ask me how I know!

 

[Northern924]

Mike does yours have dual fans? I thought the 2.7 was the same single fan 2 pin therm set up as the 2.5? Giles by loosening the bleed screw when the engine is hot you are allowing a lot of air (and hot thin air at that) back into your system, you should always bleed it cold til it runs from the screw, then run the car upto temp with the heater fans running, let it cool completely then check again, never try when the engine is hot. As its been said though, halfway at normally running then just below the top norm mark when pushing it a bit is normal, as its been said your old thermo was probably failing causing the engine to run colder than it should

 

[Sandspider]

Cheers David - I'd be interested. Paul - I thought the idea of the bleed screw is that after running the engine up to temperature and switching it off, you opened the bleed screw to release the now pressurised air / coolant. Pressure in the coolant system is higher than atmospheric pressure, so air should leave the coolant system (due to the bleed screw being at the highest point of the coolant system). I suppose a bit of air may get back in, but overall, air (and eventually water) should leave the system. I do fill it cool until coolant comes out of the bleed screw, but surely you have to use the bleed screw when it's hot? (Unless you have another way to pressurise the coolant system of course - I don't). Cheers, Giles

 

[Mike_Pollock]

My 2.7 has the twin fan set up with the 3 pin switch. Air con or not may make a difference. Best way to check is to have a look! Edit - As a general point I thinly that the 2.7s are basicly S2s with a single cam engine

 

[DavidL]

ORIGINAL: Northern924] Giles by loosening the bleed screw when the engine is hot you are allowing a lot of air (and hot thin air at that) back into your system, you should always bleed it cold til it runs from the screw, then run the car upto temp with the heater fans running, let it cool completely then check again, never try when the engine is hot.

Paul, Surely a hot, pressurised system can only allow air/water out not in? Its just like bleeding your central heating radiators is it not? The extra fluid that will take up the space of whatever comes out comes from the reservoir, assuming its full.