Volvo MD2B Not Warming Up.

whiteshythe

whiteshythe

Well-Known Member
Joined
14 Dec 2009
Messages
173
Location
Hythe Marina Village
Visit site
Hi All
Have noticed today that my raw water cooled Volvo MD2B is not getting above 50deg/C even after extensive running. I have removed and checked that the thermostat is not stuck open, also that it opens correctly at the advertised figure of 64deg/C. Have also checked the temperature gauge for correct reading.
Putting my hand on the engine confirms that it is not getting up to normal (Mid 60'sdeg/C) temperature. The Heat Exchanger and Cylinder Heads stay quite cool, and the block only luke warm. The ambient air temperature here in Southampton today is about 9 deg/C.

I have never really understood how the MD2B cooling system works, despite having a diagram to look at. There appears to be a continuous bypass for the cooling water even when the thermostat is closed. Ideas anyone, the engine seems to defy the laws of physics!
Regards,
Steve.
 
whiteshythe said:
Hi All
Have noticed today that my raw water cooled Volvo MD2B is not getting above 50deg/C even after extensive running. I have removed and checked that the thermostat is not stuck open, also that it opens correctly at the advertised figure of 64deg/C. Have also checked the temperature gauge for correct reading.
Putting my hand on the engine confirms that it is not getting up to normal (Mid 60'sdeg/C) temperature. The Heat Exchanger and Cylinder Heads stay quite cool, and the block only luke warm. The ambient air temperature here in Southampton today is about 9 deg/C.

I have never really understood how the MD2B cooling system works, despite having a diagram to look at. There appears to be a continuous bypass for the cooling water even when the thermostat is closed. Ideas anyone, the engine seems to defy the laws of physics!
Regards,
Steve.
Click to expand...

Have another look at the thermostat.......Closely!!!!!! I had this a few months ago. Removed the thermostat and put in a saucepan. It functioned perfectly. I then looked more closely and realised that Volvo had once more done unnecessary redesigning and the thermostat valve is now a circular plate. In my case the plate was not fully seating. There was something trapped. I stuck it back in the saucepan to open it and found a minute piece of scale trapped on the seat and stuck there as the thermostat could not get hot enough to open and free it. It is surprising how little water these need to cool them.

The bypass goes through a restrictor under the thermostat housing which allows just enough cold water to keep the exhaust system cool when the thermostat is closed. When the thermostat opens then water is pumped around the heads and exhaust manifold and hot water exits via the thermostat.

The water in the blocks circulates so long as there is no mud or scale build up in the base of the blocks and the wee drilled port via the head gasket near the exhaust manifold is clear. Scale in the blocks can be removed by opening the drain cocks with the engine running. Best done before the engine warms up.You will feel the crud if you put your hand in the water flow.
 
whiteshythe said:
Hi All
Have noticed today that my raw water cooled Volvo MD2B is not getting above 50deg/C even after extensive running. I have removed and checked that the thermostat is not stuck open, also that it opens correctly at the advertised figure of 64deg/C. Have also checked the temperature gauge for correct reading.
Putting my hand on the engine confirms that it is not getting up to normal (Mid 60'sdeg/C) temperature. The Heat Exchanger and Cylinder Heads stay quite cool, and the block only luke warm. The ambient air temperature here in Southampton today is about 9 deg/C.

I have never really understood how the MD2B cooling system works, despite having a diagram to look at. There appears to be a continuous bypass for the cooling water even when the thermostat is closed. Ideas anyone, the engine seems to defy the laws of physics!
Regards,
Steve.
Click to expand...

Cooling system as Bilgediver describes it.
Easy to overlook the Tee piece in the hose running under the manifold. That's where cooling water enters the engine flowing via passages in the manifold to the heads, around the heads and blocks and back out again to another passage in the manifold and finally leaving via the thermostat.

The thermostat should only just begin to open at the specified temperature.

Seal around the thermostat flange OK?

BUT you say raw water cooled but then you mention a heat exchanger! :confused:
 
Last edited:
Thank you Gentlemen for your advice.

I will do as Bilgediver has sugested and reinspect my thermostat. Logically this has to be the cause of my cool running problem. Will advise of outcome.
Well done VicS for spotting my 'deliberate mistake', I should have said 'Manifold' not Heat Exchanger!

Kind regards,

Steve.
 
whiteshythe said:
Thank you Gentlemen for your advice.

I will do as Bilgediver has sugested and reinspect my thermostat. Logically this has to be the cause of my cool running problem. Will advise of outcome.
Well done VicS for spotting my 'deliberate mistake', I should have said 'Manifold' not Heat Exchanger!

Kind regards,

Steve.
Click to expand...

You did not give any history for this engine..... WHen you remove the thermostat housing it has two cavities. The big one covering the thermostat and a lower space which covers a depression in the manifold casting. Some people see this as being a blocked cooling duct and drill it clear. This will also give your symptoms as usually this port is only drilled in fresh water cooled engines. In your engine there should be no hole there.
 
Bilgediver said:
You did not give any history for this engine..... WHen you remove the thermostat housing it has two cavities. The big one covering the thermostat and a lower space which covers a depression in the manifold casting. Some people see this as being a blocked cooling duct and drill it clear. This will also give your symptoms as usually this port is only drilled in fresh water cooled engines. In your engine there should be no hole there.
Click to expand...

Hi Bilgediver,
My MD2B fitted in a Trintella 1A is 42years old (hours unknown).I have owned it for the last 6 years. The engine has been very reliable and relatively smoke free. It has only recently exhibited the 'Cool Running Problem' prior this the temperature used to get up to about 65deg/C and I could see the temperature gently fluctuating as the thermostat opened and closed. I intend to have another look at the thermostat tomorrow.
Kind Regards,

Steve.
 
Last edited:
whiteshythe said:
Hi Bilgediver,
My MD2B fitted in a Trintella 1A is 42years old (hours unknown).I have owned it for the last 6 years. The engine has been very reliable and relatively smoke free. It has only recently exhibited the 'Cool Running Problem' prior this the temperature used to get up to about 65deg/C and I could see the temperature gently fluctuating as the thermostat opened and closed. I intend to have another look at the thermostat tomorrow.
Kind Regards,

Steve.
Click to expand...

This sounds like the problem I described. The thermostat I had was a disk which sat on a flat surface and so it was easy for
a piece of scale to get trapped between the rather flimsy disk and flat seat and allow water through. The older thermostats had a cone valve and I never had a problem with these till total failure of element. They usually lasted some years.
 
You must log in or register to reply here.

Share this page

Top