Perkins MC 42 not getting up to temperature

[rgriffiths]

We have a Perkins MC42 and the engine does not get much above 40 degrees. I have checked the thermostat in a pan of water and it only opens when the water is very hot so appears to be ok. Back in the engine the pipes to the calirofier and skin tank do not get much more than luke warm. The set up is slightly different to what I am used to - see pics - with the thermostat located behind the square block in the heat exchanger. 

Any suggestions as to what might be the problem? 

[Tony Brooks]

Is that 40 degrees from a temperature gauge or thermometer direct on the engine?

If its the former then I would suspect a cockup when the sender was changed so you now have mismatched Us and European gauge and sender. Depending upon which is wrong they tend to either read rough;y twice or half what they should. I could be a faulty gauge or sender but at present I favour a mismatch.

Test the hot engine with an infra-red thermometer to confirm the true temperature.

[OldGoat]

Could it be something daft,  as in - the calorifier and skin tank both being fed off the bypass circuit?

If so, the thermostat never comes into play and the engine is overcooled? 

[rgriffiths]

The sender is new and was matched by the Perkins guys with the guage I have. I am going to change both sender and guage to see if that is something to do with the reading at least. 

But the water through the taps is not hot at all. It could be an airlock but it is strange that the water in the heat exchanger does not get that hot (to the touch) either. I could test with a thermometer.

I don't quite understand the thermostat position. And I wondered if it is not coming into play. 

[Tony Brooks]

13 minutes ago, rgriffiths said:

The sender is new and was matched by the Perkins guys with the guage I have. I am going to change both sender and guage to see if that is something to do with the reading at least. 

But the water through the taps is not hot at all. It could be an airlock but it is strange that the water in the heat exchanger does not get that hot (to the touch) either. I could test with a thermometer.

I don't quite understand the thermostat position. And I wondered if it is not coming into play. 

I expect there is an internal drilling from the cylinder head into the manifold that the thermostat sits in and then vents into the heat exchanger.

An air lock is very unlikely to cause under cooling but if one is in the calorifier coil it could cause cool/cold domestic hot water.

As you have confirmed the engine temperature then you can rule out a gauge/sender problem but I think Old Goat may be onto something.

There is a thinner braided hose that runs form the water pump body, turns  through a right angle and looks as if it may enter the thermostat housing. If it does than I suspect this is a bypass hose and it could indicate that this engine requires a bypass thermostat instead of a normal one. Typically bypass stats either have a band around the body about 1" deep (old type) or a sort of penny washer hanging down underneath them. This blocks up the bypass when the engine is hot so on the face of it the wrong design of thermostat should cause overheating rather than over cooling but who knows. Check the type of stat required with Perkins.

Do not spend money until you absolutely confirm the engine running temperature. I assume that you are running at 1200 rpm + and in gear  to make the engine work. This weather it could take some time to get the engine hot.

 

 

[WotEver]

31 minutes ago, Tony Brooks said:

This weather it could take some time to get the engine hot.

I’m finding that with my car. The drawback of only having to drive 12 minutes to work is that the heater just starts blowing hot as I pull up and turn off. 

[rgriffiths]

It has actually been like this for a long time. I know .... I should have looked at it when it wasn't freezing outside.  

I will definitely check out the type of thermostat needed. Could well be that. The one I took out looked perfectly normal. 

[rgriffiths]

Interesting thread with a reply from the guy that designed the heat exchanger. Similar problem but not a solution it seems. 

http://the-norfolk-broads.co.uk/printthread.cfm?Forum=38&Topic=32339

 

 

[Tony Brooks]

54 minutes ago, rgriffiths said:

Interesting thread with a reply from the guy that designed the heat exchanger. Similar problem but not a solution it seems. 

http://the-norfolk-broads.co.uk/printthread.cfm?Forum=38&Topic=32339

That link kind of implied that the thermostats were not well located and held in position in that heat exchager so if its loose and tater can leak around it in any quantity it would run cool.

[The Bagdad Boatman (waits)]

Two pipes run from the engine. one before the thermostat usually runs to the heater, in a car or lorry the cab heater in a boat the calorifier. One after the thermostat  (which only opens if the engine is running hot) runs to the heat exchanger (radiator or skin tank)  from the top of the engine and the return piped to the bottom. If the engine is not working hard then it can stay cool. 

[rgriffiths]

That makes sense. Would it therefore follow then that the calirofier pipe should be hot before the thermostat opens and the heat exchanger gets hot. I wouldn't say that happens. Maybe there is a leak around the thermostat. I will take another look. 

[The Bagdad Boatman (waits)]

Check the flow through the calorifier pipe it may have degraded over time worth connecting a hose pipe and seeing if there is a through flow wet and messy I know but that is what boating is about. 

[Tony Brooks]

14 hours ago, rgriffiths said:

That makes sense. Would it therefore follow then that the calirofier pipe should be hot before the thermostat opens and the heat exchanger gets hot. I wouldn't say that happens. Maybe there is a leak around the thermostat. I will take another look. 

In general and by the look of it on your engine yes. There are a few engines that pipe the system so the calorifier is not fed until the thermostat opens. Yet others have a separate thermostat that opens preform the main stat so the engine gets hot before the calorifier  is supplied.

[Webafloat]

On 02/12/2017 at 19:08, Tony Brooks said:

That link kind of implied that the thermostats were not well located and held in position in that heat exchager so if its loose and tater can leak around it in any quantity it would run cool.

I know back in 2017 Tony, but this sounds like my issue?

Edited February 2, 2022 by Webafloat