Strange Cooling System Problem

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SteveH - 22 May 2007 22:08 GMT

After a track session at an airfield day on Monday, I was shocked to
find that my 75 had dumped a load of coolant on the floor under the car.

A quick check showed that the radiator fan switch had failed, so I
topped up the coolant, bridged the switch connectors so it ran
continuously on the ignition and largely ignored it for the rest of the
day (although I did get into the habit of cutting the engine and letting
the fan run for a while before killing the ignition from then onwards)

However, later in the day, I pulled into the Severn View services to
grab a coffee and came back out to find it had done it again. When I
parked up this time, I didn't give the car a couple of minutes to cool
with the fan on.

The temp. gauge is reading normally - never climbed above 85-ish
degrees. I know the guage is working, 'cos I've seen it climb as far as
110 degrees in traffic.

The water is coming out under pressure from one of the hose connectors
on the expansion tank.

Any ideas? - I suspect the expansion tank cap may be allowing pressure
to build in the system rather than letting it bleed away. Is this a
possibility?

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Tony Rickard - 22 May 2007 22:24 GMT

> After a track session at an airfield day on Monday, I was shocked to
> find that my 75 had dumped a load of coolant on the floor under the car.

From your experience at the track day you will probably won't be
surprised how much strain you put on the car in a competitive
environment and just how much it differs from fast road driving.

When guys talk about racing other cars on public roads quite frankly it
is just a little bit of playing compared with committed track or rally
stage driving.

I can recall running as a timekeeper on a rally event and afterwards had
to tighten loads of stuff up (including the exhaust manifold which was
leaking and sounded pretty terminal!)

Hopefully it is as simple as need to tighten up some hoses. Whether the
shaking around could have upset the pressure in the system and draining
and refilling might - but that is pure guessing :)

Hope you get it fixed soon, it would be a shame to put a damper on your
track day experience - which sounded a real blast and great to see how
competitive both the 75 and you proved to be.

Cheers
Tony

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SteveH - 22 May 2007 22:29 GMT

> > After a track session at an airfield day on Monday, I was shocked to
> > find that my 75 had dumped a load of coolant on the floor under the car.
>
> From your experience at the track day you will probably won't be
> surprised how much strain you put on the car in a competitive
> environment and just how much it differs from fast road driving.

Oh, indeed. I couldn't believe how hard you can brake if you really want
to..... so hard that the rear end was going light and wagging around a
bit.

> When guys talk about racing other cars on public roads quite frankly it
> is just a little bit of playing compared with committed track or rally
> stage driving.

So true. I've never got anywhere near that on the roads, no matter how
silly I think I've been.

> I can recall running as a timekeeper on a rally event and afterwards had
> to tighten loads of stuff up (including the exhaust manifold which was
[quoted text clipped - 3 lines]
> shaking around could have upset the pressure in the system and draining
> and refilling might - but that is pure guessing :)

Hmmmm, I'll have a look at the hoses - maybe go on a blitz and replace a
load whilst I've got the system drained to replace the fan switch.

It has been suggested that I could have impending head gasket issues.
But I'm not totally convinced, 'cos the 8v lumps aren't known for it.

> Hope you get it fixed soon, it would be a shame to put a damper on your
> track day experience - which sounded a real blast and great to see how
> competitive both the 75 and you proved to be.

Cheers - it was the most fun I've ever had in a car.

If you're anywhere near Bath, I'm back on track on 29th July....

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Zathras - 23 May 2007 08:31 GMT

>It has been suggested that I could have impending head gasket issues.
>But I'm not totally convinced, 'cos the 8v lumps aren't known for it.

After reading original post and knowing of the track day, head gasket
was my first thought! Hope it's a weak hose though!

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Catman - 23 May 2007 09:26 GMT

>> It has been suggested that I could have impending head gasket issues.
>> But I'm not totally convinced, 'cos the 8v lumps aren't known for it.
>
> After reading original post and knowing of the track day, head gasket
> was my first thought! Hope it's a weak hose though!

Could be that too, but AIUI most straight 4 Alfa lumps are actually
reasonably happy running without a gasket at all. This was (IIRC) Chris
Snowdon that I was talking to, but it was years ago, so it could have
been Jamie Porter.

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SteveH - 23 May 2007 15:35 GMT

> >> It has been suggested that I could have impending head gasket issues.
> >> But I'm not totally convinced, 'cos the 8v lumps aren't known for it.
[quoted text clipped - 6 lines]
> Snowdon that I was talking to, but it was years ago, so it could have
> been Jamie Porter.

Hmmmm.

What I don't get is that there are no other signs of head gasket issues
- ie. the temperature doesn't climb over 80 degrees most of the time,
even on the track. It does get higher in traffic on hot days, though.
There's no 'mayo' on the oil filler cap and no sign of oil in the
expansion tank.

Fingers crossed it's just a faulty expansion tank cap that's not
allowing pressure to bleed out or a weak hose connection.

Just to confuse things further - it doesn't do it all the time, either.

Very odd.

I suppose I can risk another track day to see what happens.....

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Catman - 23 May 2007 07:44 GMT

<snip>

> The water is coming out under pressure from one of the hose connectors
> on the expansion tank.
>
> Any ideas? - I suspect the expansion tank cap may be allowing pressure
> to build in the system rather than letting it bleed away. Is this a
> possibility?

Yes, HTH

C

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SteveH - 23 May 2007 15:32 GMT

> <snip>
> > The water is coming out under pressure from one of the hose connectors
[quoted text clipped - 5 lines]
>
> Yes, HTH

Well, a new cap is cheaper than a head-gasket......

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Bert Kanters - 24 May 2007 00:14 GMT

the cap is supposed to hold pressure up to about 1 bar, not let it bleed
away because pressurized water has a higher boiling point. If pressure
exceeds 1 bar or so, than the cap lets pressure off by letting water out, to
prevent hoses bursting or worse events.

>> <snip>
>> > The water is coming out under pressure from one of the hose connectors
[quoted text clipped - 7 lines]
>
> Well, a new cap is cheaper than a head-gasket......

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