1970 Volvo MD1 cooling problem

" I have a circa 1970 Volvo MD

" I have a circa 1970 Volvo MD1, single cylinder raw water cooled marine engine. I recently pulled the head off and cleaned out tons of rust and junk from the lower part of the water jacket. I put it back together and beleive it or not it runs. In place of the water drain plug I put a temp sender, because it was the only hole in the block. After running it for a while, the meter was pegged at 240 degrees but the head and thermostat housing was still just luke warm. I am getting good water flow in and out of the engine. The area around the combustion chamber is too hot to touch while the top is relatively cool, cool enough so the thermostat isn't anywhere near opening temperature. Is it normal to have such a wide temperture difference in a diesel of this type? There is a bypass channel in the thermostat housing that lets the water flow out the exhaust before the thermostat opens. Is too much water flow out and not flowing through the engine. Maybe everything is OK and I don't know it. Please help if you can, Thanks "

How hot does the bottom of th

How hot does the bottom of the cylinder feel? Is it as hot as around the combustion chamber? If the only hot area (by feel) is around the combustion chamber and all else is cool or at an even temp I would suspect the temp guage accuracy. If the area around the sender is also hot is there a chance that there was a deflector of some type that coroded away and is not causing the water to flow completly through the cooling system or a restrictor in the head gasket that is not there. Also is the thermostat still in the engine? Most engines need it to be there as it is a bypass control valve when it isn't open. Feel free to contact me via email if this doesn't help. Ernie

" Glowell, Is your MD1 thermos

" Glowell, Is your MD1 thermostat assy. mounted on front of head or on manifold as in later models? Sounds like flow pattern is reversed by blockage. More info. is needed. Glad to try and help. Dick "