mj81
Active Member
My MD5A is overheating? When I take out the thermostat there is no problem. What are the risks of running without a thermostat? I have tried replacing the thermostat but same problem!
Volvo MD5A OverHeating
- Thread starter mj81
- Start date
William_H
Well-Known Member
The thermostat is designed to bring the engine up to optimum working temperature as quickly as possible and then open to keep the temperature down to the optimum. So it won't overheat without a thermostat but will take a longer time to warm up and may run too cool. This results in excessive wear of the cylinders. You may never notice the difference or wear out the cylinders but on the other hand in cold climate it is more critical than the tropics.
So check the thermostat in a pot of boiling water you should see it open by about 3 mm then close again in cold water. If it doesn't have a new one.
olewill
So check the thermostat in a pot of boiling water you should see it open by about 3 mm then close again in cold water. If it doesn't have a new one.
olewill
VicS
Well-Known Member
The problem will be that the engine will run too cold, not only affecting performance but allowing condensation to accumulate in the oil and in the coldest parts of the engine. In extremes this can cause rusting, cracking and ultimately failure of valve springs.
It is sometimes said that running without a thermostat can affect the water distribution around the engine leading to local overheating. Not a concept that I understand i must say!
Have you checked your thermostat. It should just, only just, begin to open at the specified (marked) temperature if heated slowly in a pan of water. It may also be marked with the temperature at which it should be fully open.
I am not familiar with that engine but assuming it is raw water cooled then scaled or other wise restricted water passages are a likely cause. even if indirectly cooled restriction of the raw water circuit could be the problem.
Have you replaced the pump impeller and checked all the external pipework from inlet skin fitting, strainer, gearbox cooler etc right through to and including the exhaust injection point for restrictions.
It is sometimes said that running without a thermostat can affect the water distribution around the engine leading to local overheating. Not a concept that I understand i must say!
Have you checked your thermostat. It should just, only just, begin to open at the specified (marked) temperature if heated slowly in a pan of water. It may also be marked with the temperature at which it should be fully open.
I am not familiar with that engine but assuming it is raw water cooled then scaled or other wise restricted water passages are a likely cause. even if indirectly cooled restriction of the raw water circuit could be the problem.
Have you replaced the pump impeller and checked all the external pipework from inlet skin fitting, strainer, gearbox cooler etc right through to and including the exhaust injection point for restrictions.
VicS
Well-Known Member
As the question has been duplicated why not delete the other one
Mudhook
Well-Known Member
I had an identical problem recently with my MD7A. It turned out that there was a big blob of sealant in the joint between the cooling water pipe from the pump to the thermostat. There's another way for cooling water to get into the manifold so it was working sort of ok until the thermostat failed to open. This may not be directly translatable to the MD5 but it might help. Check the amount of water coming out of the exhaust. In my case it was noticeably lower than usual.
Regards, Mudhook
Regards, Mudhook