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Overheating again

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Like many others, I have had overheating problems in the Eclat, I have two fans, ok thermostat and well flushed system, I rang Mike Taylor and he was full of gloom talking about cracked liners and blown gaskets, I had no gas bubbling out of the rad filler cap and no mayonnaise in the sump or gas coming from the oil filler.

I found that I had a vapour lock in the top hose leading to the thermostat housing so loosening the jubilee clip and pulling the hose off and filling both the casting and hose. This solved the problem but after a long run I suddenly had overheating again. 

Much head scratching revealed that the fuse was overheating at its terminals, this caused the fuse body to soften and collapse slightly so the fans stopped, on cooling down the contact was restored. I cleaned the terminals to reduce the volt drop however there was still overheating so I temporarily put in a solid link , £1 coin, and this solved the problem so I need to rethink the fusing.

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The fuse is overheating but not blowing?

Poor connections in the fuse box perhaps.

Can you measure resistance of the fans, and current?

I'd try an unswitched separate fused feed to the fans, see if it behaves,  to try to eliminate the wiring or the motors.

Also though I thought the fans are only necessary when standing or crawling,  so if it overheats on a run  the engine is producing too much heat?

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I am running at just to the right of centre on the gauge in the recent hot weather. The fans come on and off when standing idle and at a fast tick over,I think this is OK.

The problem is with the contact between the fuse and the holder but I have cleaned and polished the surface but still the holder (the actual brass spring clip) is hot to the touch when the fans have been running a while.

I think that I will explore a separate fuse arrangement for the fan supply, I am pretty happy that the fan motors are not drawing to much current as the fuse doesn't blow.

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Overheating fuse but not blowing is the typical symptom of a sustained overload.

I wonder are the fans just running for too long a period.

Where I am going with this is that the fans might be over worked due to another issue in the cooling circuit.

I remember I once had an issue with overheating on my Eclat and after much head scratching I eventually found the the boss that is pressed onto the pump shaft that the pulley wheel is connected to was turning while the pump shaft was not. The tolerance between the impeller and its housing is very small and when the boss moved, the impeller would jam and so stop pumping, then it would move and pump again. Because I had an overheating problem, my runs were short, so it took fooking ages to see this issue. A replacement pump soon after sorted that issue.

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12 hours ago, black eclat said:

Overheating fuse but not blowing is the typical symptom of a sustained overload.

I wonder are the fans just running for too long a period.

Where I am going with this is that the fans might be over worked due to another issue in the cooling circuit.

I remember I once had an issue with overheating on my Eclat and after much head scratching I eventually found the the boss that is pressed onto the pump shaft that the pulley wheel is connected to was turning while the pump shaft was not. The tolerance between the impeller and its housing is very small and when the boss moved, the impeller would jam and so stop pumping, then it would move and pump again. Because I had an overheating problem, my runs were short, so it took fooking ages to see this issue. A replacement pump soon after sorted that issue.

I'm not sure that it is necessarily overload. I have the problem intermittently on my car on more than one fuse. The glass fuses and holders do not seem to make a sufficiently good connection, which gets hot when load is applied. I have applied Tim Engels' suggestion of a cleaning fluid that supposedly works very well on model railways. It needs to sit on the surface for a few hours; I applied it last weekend and will find out if there is any difference next time I take the car out.

Ultimately, the solution is probably to replace the fuse box with a blade fuse box.

Richard

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Thanks Mike.

My testing has been with the car stationary, the car gets up to 'fan' temperature , i.e. Just over 90 degrees on the gauge and the fans come on,. Quite quickly they go off again, when things settle down, they run for no more than half the time, the fuse holder gets hot while this is going on but only at one end. I have cleaned the holder as best I can with wire wool contact cleaner etc. The fans turn freely and the water pump is in good order, it was rebuilt by Lotusbits recently and checked when refitted to my rebuilt block.

My next experiment is to to solder a wire to each side of the fuse holder and run these wires to a separate new fuse holder and try that.

Peter

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If the wires connecting to the fusebox are the originals then they could easily be so old and crusty,  with breaks in the copper strands, and might be the source of the heat?

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Hi Peter, I have seen fuse holders where the part that holds the fuse has loosened where it is riveted through the Bakalite to the terminals where the wires attach, I would be checking this as it  could be causing the resistance that is causing the holder to get hot. You could try disconnecting the wires at the rear and fitting a blade fuse behind as a test to see if you get the same symptoms.

regards Dan

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Thanks Dan

I have soldered a wire to each blade of the fuseholder and run them to a floating fuseholder to see if this solves the problem, when it stops raining I will do some more tests.

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