Engine intermittent overheating problem

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Gerry

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www.gerryantics.blogspot.com
Hi folks

We have a Perkins M50 Diesel (aka Mitsubishi, Detroit Diesel, Northern Lights and a few other re-brands). It is overheating intermittently after about forty minutes running. This is probably not the impeller or heat exchanger or thermostat. I have checked these. We are not seeing any loss of coolant. We ran without the thermostat and it stayed cool.

The antifreeze did look a bit mucky... could this be dirt in the cooling water (not raw water). It diverts to a calorifier, could there be some kind of problem with this? Could dirt mess up the thermostat and would this show up in flicking of a temperature gauge?

The way the temperature gauge flicks up and down (much faster than the temperature could possibly change) might mean this is a temperature sender problem. The sender seems to have two spade connections.

Does anyone have any other thoughts/suggestions?

If it is a sender problem, is there anything uniquely Perkins or "marine" about a temperature sender and would a lower-cost car part do just as well? If so, does anyone know what the generic equivalent part might be and what I should ask for?

We are currently in Central America and marine parts are not easy to find.
 
"dirt in the cooling water"--how long since the fresh water coolant was last renewed? If it looks mucky it is worth renewing anyway. You can do that when you renew the thermostat as if it stayed cool when it runs without one that suggests a thermostat fault.

The most likely cause of the flicking of the gauge would be a loose contact.

Many marine engines these days are automotive or industrial conversions. If you see one in a truck or van that looks like yours, then it is probably the same base engine. I have had lots of cooling problems on cars and vans over the years. At one time thermostats failed open and the engine ran cold. Now they tend to fail closed and the engine boils. I have had limited success in getting temperature senders to work, so much so that I designed my own based on a small platinum film sensor (you want a PtR100 sensor available from a good electronics supplier) and a few resistors arranged as an unbalanced bridge. Reading the imbalance voltage gives an indication of temperature of the engine block or anything else that you clamp the sensor onto.
 
Gerry said:
Hi folks

We have a Perkins M50 Diesel (aka Mitsubishi, Detroit Diesel, Northern Lights and a few other re-brands). It is overheating intermittently after about forty minutes running. This is probably not the impeller or heat exchanger or thermostat. I have checked these. We are not seeing any loss of coolant. We ran without the thermostat and it stayed cool.

The antifreeze did look a bit mucky... could this be dirt in the cooling water (not raw water). It diverts to a calorifier, could there be some kind of problem with this? Could dirt mess up the thermostat and would this show up in flicking of a temperature gauge?

The way the temperature gauge flicks up and down (much faster than the temperature could possibly change) might mean this is a temperature sender problem. The sender seems to have two spade connections.

Does anyone have any other thoughts/suggestions?

If it is a sender problem, is there anything uniquely Perkins or "marine" about a temperature sender and would a lower-cost car part do just as well? If so, does anyone know what the generic equivalent part might be and what I should ask for?

We are currently in Central America and marine parts are not easy to find.
Click to expand...
The Perkins M50 is rebadged as the Volvo Penta MD22 and was used in the Maestro/Montego cars in the UK. It was developed from the Maestro/Montego petrol engine and is a lo compression (17ish to 1) diesel engine. It certainly had nothing to do with Detroit Diesel (they were two stroke engines) or Mitsubishi.
It sounds as if you have several issues here, the temp gauge will be one and is probably an electrical prob. The second one is a blockage in the fresh water system, you proved that by taking the thermostat out and it ran ok. The coolant shouldnt be cruddy, and so you need to flush and clean the system. Be careful, use a recommended flush liquid because the head is aluminium. No harsh acids!
Stu
 
If the gauge is flicking over suddenly, faster than the temprature could change then its definitely an electrical fault of some kind. Often the sender. If the sender is earthed it will have a single terminal connected to the guage. When the gauge has flicked over - if it stays long enough, pull the wire off the sender. Chances are the gauge will stay at hot. if so theres a short in the wire, or a fault in the gauge itself. You might find just moving the wire causes the gauge to give erratic readings, if the wire is shorting. If the gauge consistently drops to zero when you disconnect the sender, then the sender is duff. I can not remember what the Perk sender spec was, but there are usually only two or three types on older engines, and an auto spares stockist out to be able to match it for you.

There is a second type of temprature gauge, where the sender has two terminals, one of which goes to the ign switch + on, the other goes to the gauge, and often these have 3 terminal meters. These will usually show zero if the wire is shorted, and can show full scale or zero when a fault develops, depending on the circuit used.

Great fun wiring faults, have fun, and good luck!
 
Fascinating! It has an overhead cam shaft which made me always suspect that it was a converted petrol engine.

When I flew in to Trinidad,from the UK, heat exchanger rubber end caps from Perkins I discovered they were identical to the Detroit Diesel and northern Lights parts and that they were all the same engine, originally Mitsubishi.
Another yachtie told me he saw the engines coming off the Perkins assembly line in the UK in various colours including Caterpillar, Rolls Royce and I think Cummins! The thermostat seems to be a standard automotive part although the workshop manual says it should run 10 degrees F cooler in the marine than in the automotive diesel form.

I will test the senders, they have two connections, if anyone knows what a suitable part number or descriptions I'd be pleased to know!!

Thanks for your help.
 
Gerry

I am in the Rio Dulce and have a Temperature gun if it of any use (I am at Brunos, the boat is at Abels). The gun is at Texan Bay but I am sure I can arrange to get it up river if you are interested

Phone me on 4584 3961 or leave a message for Triumphant at Brunos if you are interested
 
From the information given in the OP I would make an educated guess that the problem lies with the temperature sender.
My reasoning is that if the gauge flickers at normal running temperatures but shows "cool" when the thermostat is removed it is only indicating a fault at higher coolant temperatures, to me this implies that is being sent an intermittent/faulty signal by the sender unit, and this is not happening when it is not being heated up by the non-thermostat regulated coolant.

Good luck!
 
Gerry said:
Fascinating! It has an overhead cam shaft which made me always suspect that it was a converted petrol engine.

When I flew in to Trinidad,from the UK, heat exchanger rubber end caps from Perkins I discovered they were identical to the Detroit Diesel and northern Lights parts and that they were all the same engine, originally Mitsubishi.
Another yachtie told me he saw the engines coming off the Perkins assembly line in the UK in various colours including Caterpillar, Rolls Royce and I think Cummins! The thermostat seems to be a standard automotive part although the workshop manual says it should run 10 degrees F cooler in the marine than in the automotive diesel form.

I will test the senders, they have two connections, if anyone knows what a suitable part number or descriptions I'd be pleased to know!!

Thanks for your help.
Click to expand...
OK I stand by my original statements, forget about DD, Cummins etc, your mate was full of kaka.
The original Perkins/VP had an intercooler with rubber caps on the end, they were a std intercooler used by others.
Stu
 
OK chaps this gets curiouser and curiouser!

Changed the thermostat to a caterpillar one, ran fine for 40 minutes then soared to the right...

Drained and changed coolant fluid. No loss there at all. Old stuff pretty mucky though.

Cleaned and reattached all connectors to the temp sender.Ran fine then overheated after 40 minutes- again!

Today changed fuel filter, cleaned out some water and fuel looked a bit mucky so took off bottom gallon or so. ran for 20 minutes then showed overheat AGAIN!

There is no sense that the engine block is hotter than it should be. No smell of burning oil. No loss of oil or coolant. Small amount of white smoke on initial engine start-up but soon clears.

The gauge moves slowly to running temperature holds there and then swings very quickly to the right, but not to the extreme right. Ends up about 3/4 way over. AAAggghhh.

Any ideas? The husband is getting a little despondent!
 
I'm still suspicious of the sender unit as it could be "breaking down" after a certain time, but I suppose that you could have a blocked waterway somewhere, although this is fairly unlikely on a secondarily cooled engine.

I don't know if they are still available, but various outboard manufacturers used to sell temperature sensitive crayons which would change colour as the temperature rose, when applied to various parts of the engine they would give a pretty reasonable idea of where the coolant was flowing - or not as the case may be. They were available in several different temperature ranges.

I'm clutching at straws here, but have you got the correct type of thermostat, ie "normally open/closed"? Or, bearing in mind that I'm not familiar with these actual engines, is there any way it could have been fitted wrongly?
 
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