one problem after another

[heliosuk]

Viscous fans usually seize so overcool, so they were wrong there.

QUOTE]

 

Sorry Conniff, have to disagree there. The explanation further on is correct however as you correctly point out but bilt in is a failsafe so this shouldn't happen. If it does happen that the clutch so to speak binds or seizes this is very apparent as sounds like a jet engine and the consequential drag pulls down fuel consumption like no tomorrow so to speak. If it had failed in this mode it would have been blatantly apparent to not only the owner but the garage itself.

 

I think out of the countless cases of viscous couplings I have changed and come across I can only recall two that have locked and one of those had a self tapper through it!!!

 

The cat will affect running especially if it has collapsed but will not cause an overheating problem. As you know and point out, the lambda sensor is purely a measuring device so is nebulous to actual mechanical issues.

 

This is a very odd one indeed.

 

Perhaps the op could give a few more details as I'm not aware that mercs put engine and transmission control units under the rear seat. Body control etc yes.

 

Smoke could be new parts of exhaust paint burnig off.

 

All seems a bit odd to me at the moment me thinks.

[heliosuk]

True Connif it does happen and the other instance I came across just happened to be an XJ12 where it locked and went through the radiator. Perfect hole though!! Interestingly it must have been of the same era as your SD1.

 

The smoke problem does mystify me ( which is expected with smoke I suppose) as even if appeared before the exhaust system had changed does not tie up with normal (thermal incidents).

 

Too vauge at the moment perhaps?

[heliosuk]

Thanks for that suf as it confirms my statement on the coupling. If the mechanic was brave enough to stick his hand in there then the coupling is shot and is perhaps might have been the cause of the original overheating. If the fan was locked or working normally and he put his hand in there then he would be pretty "armless by now"

 

It's not unusual to have a coupling failure in conjunction with a head gasket and the garage should have isolated the fan fault first though this is not easy to do at idle depending on speed. I've seen it time and time again. Generally one would go with this type of fan first.

 

The problem I'm trying to get my head around is the smoke as I can't see how it is related. Can you give an indication of the smell? There are very disticnt differences in them.

[heliosuk]

Just had a thought, is it an automatic by any chance??

[heliosuk]

As regards looking up the coupling, wiki conniff has explained it well in the operation only emitting that they are designed to fail as yours has done. But as we know there are times when it goes the other way and will lock up but believe me you'd know it. In fact, when locked the noise is incredible!

 

Heat shields from a car of that era would be expected over the silencers/expansion chambers but not necessarily over the pipes.

 

The smell from electrical items burning is quite disticntive as is that of clutches/brakes etc. It's as such that you can tell it on a motorway with lorries etc. As also is rubber.

 

The fact that it smelt like a bonfire does start to point me towards a gearbox failure and you vibration faults along with overheating.

 

When you have been able to enjoy the car so to speak have you noticed any change in the way it shifts gear?

 

The symptoms are starting to tie up now and do link in with overheating of the engine as well believe it or not. Can you confirm if the wiring to the units under the seat showed signs of wiring melting etc and if they do is the melting consistent all around the wire or just underneath?