Overheating Volvo MD3 Engine

[Guest]

My MD3 engine is overheating in a cyclical way. Have checked water inlets, new thermostat and new impeller. Engine warms up and then guage goes quickly to very hot (in the red). After five seconds a lot of steam comes out the exhaust and the temperature drops down before slowly going up staying at normla before suddenly gettingonto the red again, and then goes thorugh the whole cycle again every five minutes. The alrm does not go off at all. Water sems to come out the exhaust and there is no change in the engine note. HELP I can think of nothing else. Any suggestions welcome. Is there a Volvo helpline for techncal support?
THanks

 

[chippie]

I would check that there is no internal collapsing of the exhaust hoses. Check the impeller again as occasionally the central boss will strip away from the rubber even on a newly fitted one. You could try running it wthout the thermostat for a short period to see if it made any difference.

Good luck


<P ID="edit"><FONT SIZE=-1>Edited by chippie on Sun Jun 2 23:27:36 2002 (server time).</FONT></P>

 

[ccscott49]

I get the distinct impression of a thermostat fault, but could be a lump of blockage, moving about??

 

[Strathglass]

Have you had previous impeller problems ?
Bits of rubber from broken impellers can cause all sort of funny cooling problems.
Iain

 

[Guest]

Thanks everybody - its sorted. Not had the boat long and previous owner said he had some trouble. Unbelievable! I noticed that the main inlet through the heat exchanger on the block did not have a hole to correspond with the one in the cover to the thermostat. It appears that it must have been corroded and someone has very neatly welded it up but left no apperture. I drilled through to the chamber behind and put the thermostat back and SORTED. The number one cylinder has obviously not been receiving any cooling for some time. The engine has always run hot. But now it is running at the right temperature and no cyclical overheating at all. Lesson is always to believe there is someone more stupid than yourself out there!!!

Thanks again for your help.

 

[bedouin]

I had similar problems on an MD2 - fixed by fitting a new thermostat (though the temperature still wanders a bit).

Like you, I noticed that there was no hole in the block corresponding to one in the thermostat housing, but I think that that is how it's meant to be. I'll check the manual next time I get to the boat.

 

[scottie]

early volvo cooling system was through the manifold to thermostat housing but later engines had an external hose with a tee piece underneath the manifold
the original hole was not used and left blocked but still needs an o ring as both housing and manifold have a recess