Cooling problem - any ideas?

[Joss Walker]

Hi guys

I need help from someone with a greater understanding than mine (shouldn't be too tricky)

Took my car (91 S2) to work yesterday, I haven't driven it on any long runs for a few years now (!!!) so 90 odd miles on the M1 and M25 each way and I had overheating problems. If I didn't keep the heating on full then my needle moved right up into the bottom of the red zone, even with the heating on it kept moving up and down between a dead horizontal position and up to almost touching the red, and this was fluctuating every minute or so the whole journey home.

Coolant is at appropriate levels and doesn't seem to leak at all, I just undid the bleed screw (with heater turned to high heat but engine not running) and the only thing that ran out was coolant. Water pump was replaced about three years (probably 1,000 miles) ago.

Any suggestions what the problems may be? I want to drive it all the time with this weather but am anxious about any long journeys

Thanks

Joss

 

[PSH]

Hi Joss

check your fan switch and the wires that go to it, I'm guessing that the S2 uses the same radiator as the turbo so the switch should be low down on the passenger side of the radiator.. the only time that I've had a similar issue ( twice in my ownership) it was down to the switch or it's wiring. Our cars are getting on a bit now and the wires will begin to fail, they will certainly be suffering from high resistance .

Pete

 

[Joss Walker]

Sorry, should have mentioned that the fans seem to work fine, can't really tell when I'm driving but when I park they are still spinning away quite happily

 

[PSH]

are you getting full speed though? it's very hot just now and the first speed setting may not be enough to keep the car cool, check that both speeds are working correctly..let the car cool down and then check...first fan on mine comes on just after the first white mark and tends to keep the needle in that area during normal driving...if it's a hot day and your needle goes over the last white mark the twin fan should kick in and bring the temp back down pretty rapidly..

Pete

 

[GlennS]

If I didn't keep the heating on full then my needle moved right up into the bottom of the red zone, even with the heating on it kept moving up and down between a dead horizontal position and up to almost touching the red, and this was fluctuating every minute or so the whole journey home.

Hi Joss,

To me it sounds like an issue with the fan control switch in the radiator. I had the same problem with my S2. The S2 has two speed fans, low speed should kick in at @ 3/4 on the gauge and bring it back down to "normal" [I should add that most 944 gauges read low]. High speed kicks in at just below the red. What it sounds like to me is your slow speed is never kicking in. The engine then heats up to just below the red when the second output from the switch puts the fans into high speed mode which brings your temperature down. My money would be on replacing the fan switch in the rad.

G.

 

[Joss Walker]

Thanks, I didn't know about the two speeds, when I park both fans are going but I don't notice either come on when I drive (I hardly ever drive it with the roof up so there is so much road noise that I don't ever hear the fan). My temp gauge has always shown that the car seems to run hot, the needle is always pretty high, I had RPM flush the system for me about 5 years ago in the hope that may help but no real joy achieved there.

So my first port of call will be to change the switch and hope that helps.n should be cheaper than a radiator because I also wondered if my radiator is just rubbish, I don't know how I would tell if the coolant isn't leaking but half the rad is bunged up.

 

[robwright]

I would tend to agree with some sort of cooling fan issue. The fans can run quite a lot on these cars even without you knowing. You only notice the second kick in traffic and as Pete says you will temp reduce rapidly. For now I would rule out a thermostat issue as this would normally result in a catastrophic cooling issue. The fact the fans are running suggest that water is at least getting to the radiator.

 

[pauljmcnulty]

I'd agree that it's probably the fan, but don't discount bleeding the system properly.
Mine was overheating to the point where the garage wondered if the HG had failed. It was just down to an airlock that took a specialist who knew how to bleed it to get all the air out.

 

[robwright]

Does it sound like there is a gurgling from the heater vents when you accelerate from stand? Especially when the engine is cold. If so then it requires bleeding. It would have to be pretty bad to cause serious overheating though I think. I have applied the steam vent mod to mine to eliminate as many air pockets as possible. Still doesn't make the bleeding process any easier though.

 

[Waylander]

This Might Help

http://www.clarks-garage...shop-manual/cool-01.htm

 

[Joss Walker]

As ever, thanks for all your responses:

Waylander, that link is very useful (if only I could get the plug off to complete the bridging activity!) but I will be doing a load of digging around there to learn other stuff too. however other 'techniques' (driving around a bit and then pulling over and popping the bonnet) have shown that the fan comes on when the temp needle is just beneath horizontal so that would seem to imply that speed 1 is working OK

Rob - it gurgles!!! therefore I think you are on the money, I've tried bleeding but only get coolant out, I am in search of a hill so I can park at an angle and see if that helps, otherwise I'll look in the FAQS I'm sure other people have had problems bleeding these too. If worse comes to worst I think I will flush the radiator with the old faithful Holts Rad flush stuff and get my Indie to give it a go changing the coolant.