Overheating inboard symptoms.

[jamie N]

My engine's a Renault Couach RC8D, 8hp/6kW, and over the winter I've altered the cooling system from 'Raw Water', to a raw water heat exchanger, with 'glycol' engine coolant. I've put a thermometer in line with the glycol coolant, and it's giving me a reading which varies appropriately, so far as I can see. The engine coolant is around about 500cc including the heat exchanger, pumped by a 2 litre/min electric 'Universal Fuel Pump', hopefully giving a circulation of the coolant 4 times a minute. The raw water coolant is engine belt driven, in the usual way, pumping through the 22 kW heat exchanger and out through the exhaust. The engine's been run at load for an hour or so over several occasions, and I've 'inadvertently/ daftly' had it running without the raw water coolant through the heat exchanger, due to a memory and checking malfunction, where the indicated temperature rose accordingly, then decreased swiftly once the seawater cock was opened.
My question is this, that without any instrumentation, what are the symptoms of a diesel engine beginning to overheat? Is it misfring, loss of power, 'smokiness'?

 

[jamie N]

I'm genuinely surprised that there were no responses to this query, given the amount of comment concerning Diesel engines on these fora. I asked the owner of our local garage, a very experienced mechanic, with his immediate response being "Smell; you'd smell it on a boat, and you'd 'maybe' sense that something's not right as the sound 'might' change, and it 'might' feel a bit different".
Seriously, I really was expecting something more 'definite'!

 

[earlybird]

Didn't notice your earlier post, but I would say that you might not notice anything until some damage is likely, e.g. head gasket failure. Smell of a hot engine might just be noticeable, but I wouldn't bank on it providing a timely warning. If the engine started misfiring or smoking then I'd be seriously concerned. Much better to provide some instrumentation on the water jacket and also perhaps the exhaust. Externally mounted alarms and switches are plentiful and cheap on Ebay.

 

[DownWest]

I didn't see this either. Overheating on a single donk might be labouring and black smoke, just before it siezes. Doubt you would notice the smell from heating, but it might sound a bit loud..

Best put in some sort of heat sensor on the primary side. Or, one just after the injection point on the exhaust to tell you if there is no raw cooling water going through.
Not many of those Renault engines about now. Same as the BMW versions of the Hatz base industrial engine.
How do you generate 12v power? The iffy internal coils, or a belt driven alternator?

 

[CAPTAIN FANTASTIC]

The engine will smell burning oil and eventually will seize up. LCD Temperature gauge instruments cost only a few pounds on ebay, can be installed on manifold /cylinder head/inlet/outlet to give you early warning.
https://www.ebay.co.uk/itm/Digital-...868222&hash=item33eb593946:g:db0AAOSwenlbB-mI

 

[KenMcCulloch]

We had a problem with a Bukh DV36 overheating. One of the hoses in the (freshwater) coolant circuit had partially collapsed. That caused restricted flow, such that at low revs, up to about 1200 rpm, nothing much happened out of the ordinary. After 20 minutes or so at 2000 rpm the temperature gauge started to creep up and, weirdest of all, the calorofiier prv started to discharge fresh water.
The point really is that the signs of overheating in a marine diesel, generally lightly loaded and running at constant speed, are quite different from what you might expect in a vehicle engine. I think if your engine was overheating due to lack of raw water, before long you would smell the exhaust starting to heat up. I don’t know if a rubber exhaust hose will actually catch fire but I do know they start to smell pretty horrible without water cooling the gases.

 

[Biggles Wader]

I'm genuinely surprised that there were no responses to this query, given the amount of comment concerning Diesel engines on these fora. I asked the owner of our local garage, a very experienced mechanic, with his immediate response being "Smell; you'd smell it on a boat, and you'd 'maybe' sense that something's not right as the sound 'might' change, and it 'might' feel a bit different".
Seriously, I really was expecting something more 'definite'!

In the absense of any alarms or guages I think your mechanic has it right. The engine will smell "hot" lose a bit of power and develop a bit of a louder noise or even a rattle. If you dont notice that happening it will boil up and stop.

 

[VicS]

I'm genuinely surprised that there were no responses to this query, given the amount of comment concerning Diesel engines on these fora. I asked the owner of our local garage, a very experienced mechanic, with his immediate response being "Smell; you'd smell it on a boat, and you'd 'maybe' sense that something's not right as the sound 'might' change, and it 'might' feel a bit different".
Seriously, I really was expecting something more 'definite'!

The first symptom you might notice is that the coolant will boil , lifting the pressure cap and being ejected into the bilges . Disconnect yours car's cooling fan(s) and you should be able to simulate the effect while stationary, except that all the coolant will end up on the ground

If there is no raw water flow you will also notice at some stage that the uncooled exhaust gases burn the exhaust hoses and any plastic components in the exhaust system

 

[jamie N]

I didn't see this either. Overheating on a single donk might be labouring and black smoke, just before it siezes. Doubt you would notice the smell from heating, but it might sound a bit loud..

Best put in some sort of heat sensor on the primary side. Or, one just after the injection point on the exhaust to tell you if there is no raw cooling water going through.
Not many of those Renault engines about now. Same as the BMW versions of the Hatz base industrial engine.
How do you generate 12v power? The iffy internal coils, or a belt driven alternator?

There's a cheap little LCD gauge on the 'Glycol' liquid side of things, which does 'seem' to show the appropriate temps. You're quite right about there not being that many RC8D's around, despite there being plentiful spares, such as rings available from Hatz suppliers, but the design was extremely prone to internal corrosion, thus the 'waterless' primary cooling fitted this winter.. The engine that I've got has an alternator, which works well, but isn't connected until the engine's running, such is the power output!