My 97 528 started over heating about 3 weeks ago. The viscous coupling had
gone so it was replaced just over a week ago. I took the car on holiday,
driving in various road conditions, and there were no problems. Suddenly on
Sunday after having driven about 40 miles the guage rose and I stopped the
car. The AA came out and filled the expansion tank and bled the system.
The problem went away - until this morning when it happened again. I filled
it up, bled it again and ran it on idle for quite a while - no problems -
after cooling checked the water level - OK. Did the same again - OK. Drove
the car for 10 miles and it overheated again. Filled up etc agaoin and the
problem was cured.
The exhaust gas test has been done - nothing found.
No oil in water.
No water appears to be getting into the oil.
No weird exhaust emmisions.
What can be causing what appears to be a pressure build up - could it be the
thermostat? COuld air be getting into the system somewhere? The water pump
has been replaced.
Can anybody help.
My 1954 Ford V8 had much the same symptoms. It turned out to be a cracked
head. You may only see the water go away when the engine is under load.
Thus, the only result will be unexplained water loss. You may not see
strange exhaust emmisions because steam is hard to see. You may not see
water in the oil.
You should get a compression test done because that will check the rings,
valves, and head.
Yes, you are certainly correct about the high cost.
The only time that the old Ford lost water was while it was being driven.
There was never any trace of water anywhere, and the engine never leaked
while it was idling.
I believe that the crack happened as a result of delayed valve repair.
However, it might have been a flaw in design. 1954 was the first year of
production of the Ford OHV V8.
The E39 has a cooling system that isn't designed for longevity. The
radiator, water pump and thermostat all start to cause problems in the
60-90K miles range (lower end for V8's, higher for I6's). You've replaced
the pump? Probably look elsewhere. That coolant is going somewhere
(although it can take a couple runs to get all the air out of the system
after a drain and refill).
The radiator plastic will develop cracks, particularly in the upper hose
fitting. Check the thermostat and its housing (I think there's an
aftermarket aluminum housing for the M52), a preventative replacement would
be a good move if it hasn't been replaced already.
Check all hoses. If they're original, they're of the age where leaks can
If the fan clutch has failed, it'll overheat in stop and go traffic, then
cool when moving at speed. If you've been running the A/C on a warm day
(mid-March?) an aux fan failure can cause the temps to go up.
A pressure test on the cooling system would be a good idea.
A cracked cylinder head is a possibility if one of the overheating episodes
was significant (it doesn't take much on these cars). Tell-tale is water
vapor in the exhaust, particularly on start up (personal experience there,
albeit with an E12). Or it could be the head gasket (the less expensive
failure). We'll hope you parked it sooner rather than later when the temps
began to soar.
The temp gauge on these cars doesn't really reflect actual engine
temperature. The normal straight-up indication covers the entire spectrum
of acceptable temps (it won't move for minor variations). When the coolant
reaches a certain level of "hotter than normal" it will finally climb into
the red. This can be quite rapid, accompanied with the instrument panel
warning light. When this happens, the car has to be parked ASAP (you don't
have time to drive 5 miles to the next exit) or the engine will be damaged
severely and expensively.
R / John
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It could just be a small leak somewhere, from the new waterpump or
from the rad etc etc caused by the initial overheating. (Are you
*sure* it was caused by the fan in the first place?) I guess if
somebody put cold water into a dry overheated engine then it could
have done some damage.
Run it at idle or high idle and feel the hoses to see what's going on
with the thermostat, waterpump etc. ...or drive it from cold a short
distance and then check for water loss before it's warmed up. If you
put neat anti-freeze in the car you can sometimes smell it in the
exhaust and/or it'll come out a different colour to regular steam if
there is a head gasket or head problem.
Thanks to everyone who replied. It appears that it is not losing coolant
but is bubbling and losing it through very high pressure out of the
expansion tank cap. If the car is operated for short distances or left
overnight etc. no coolant is lost. I've now replaced the thermostat and its
housing. The originals were still in situ.
I drove it 15 miles and everything wasa fine. Fingers crossed.
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