Thermostat and thermostat housing

[pbmaise]

While replacing all hoses on my engine, I worked my way around to the thermostat housing on my marinized Isuzu 6BD1.

It appears someone at one point attempted to use a hose too big for the job and I found the pipe connection of my thermostat housing had a crumbling powder all the way around. I suspect something like Permetex create a gasket was used.

I removed the housing and will take to the machine shop so the pipe connection can be built up with welding rods and then remachined.

It is obvious to me the thermostat gasket needs to be replaced.

My question is should I replace the thermostat at the same time?

Or if the thermostat is working why bother replacing?

However, this leads me to the question how do I know my current thermostat is working?

I can report my engine maintains a very steady temperature of around 155 F.

[pbmaise]

Note: I was able to find many thermostats for my engine described as being 82 C thermostats. That is about 180 F.

My engine never runs near this temperature hence I am concluding perhaps I should change the thermostat.

[brianlara 3]

An ancient mechanics advice : If you can afford to have your thermo housing welded/machined, then you can afford to renew the thermostat.
Thermostats are as important as oil pumps. Oil pumps can be examined for wear but thermos can be tested today as opening at the rated temp.....and tomorrow they can seize in any position from fully open to fully closed. They know no rationale.
Your new thermostat, providing it isn't a cheap import, is bloody cheap insurance.

[boatbod]

Welding a cast part is a challenging and not always successful process. You didn't say what base metal, but I'd guess aluminum from the white powder residue? Might be cheaper to buy a new housing, gasket and stat all at the same time.

[pbmaise]

Thanks for advice will replace thermostat.

I also am a bit slow and finally noticed the housing is aluminum. That crumbling whitish powder may be aluminum oxide.

Yes! Replacing the housing sounds wise too, however the housing appears customized for the marinized engine. Housing in manual and online are different.

Now it looks like I am faced with best way to rebuild area where aluminum is missing.

Will take to same machine shop and ask questions.

[pbmaise]

boatbod,

Instead of trying to weld aluminum to cast aluminum how about the following:

1 Wire brush hose connection area down to bare metal.

2. International two part epoxy Prime Etch

3. Build up area with wraps of fiberglass impregnated with epoxy

4. Machine round on lathe

Would this be a safer repair then building up with aluminum?

[boatbod]

Pbmaise, in a pinch you might try Marine Tex or a similar high-temp epoxy putty. I don't think regular epoxy or fiberglass would be much use as it cannot take long term exposure to heat.

I don't know the shape of the part, but maybe a machinist could mill a new one from a piece of billet stock?

[shakey doug]

Has any one asked if you have a raw or freshwater cooled engine prior to advicing suitable thermostat?

[pbmaise]

Originally Posted by shakey doug

Has any one asked if you have a raw or freshwater cooled engine prior to advicing suitable thermostat?

I have a raw water cooled "system" . Salt water goes into a heat exhanger to cool the radiator fluid that goes into the engine.

My manual confirms I should use a thermostat that opens between 80-84 C so I gather a 82 C thermostat is good.

[shakey doug]

If you 100% sure 155f is the true temperature of your Freshwater based coolant the circuit requires a 180f Thermo. Saltwater [Raw] cooled engines use a much lower value Thermo to alleviate water jacket salt based restricting deposits.

[boatbod]

Originally Posted by pbmaise

I have a raw water cooled "system" . Salt water goes into a heat exhanger to cool the radiator fluid that goes into the engine.

My manual confirms I should use a thermostat that opens between 80-84 C so I gather a 82 C thermostat is good.

82C is right around 180F, which would be correct for a fresh water cooled diesel engine.

[pbmaise]

Originally Posted by shakey doug

If you 100% sure 155f is the true temperature of your Freshwater based coolant the circuit requires a 180f Thermo. Saltwater [Raw] cooled engines use a much lower value Thermo to alleviate water jacket salt based restricting deposits.

I found a 2010 by Doug (same Doug? ):

Join Date: Nov 2009
Location: Between Block Island and Bahamas
Boat: Marine Trader 40' Sedan Trawler, 1978. WATER TORTURE
Posts: 715
A: call it "raw water cooled" (instead of salt water cooled), to distinguish it from a "closed loop/heat exchanger" system. You see, if you are in a fresh water lake, your "salt water" system would be using fresh water. So, to say "raw water" means that everyone understands you are referring to a system that uses cooling water that comes from outside the boat, be it salt of fresh. The water that surrounds a the engine block in a closed loop/heat exchanger system is commonly referred to as "fresh water".
The main problem with raw water cooling in a salt water environment is that the salt will begin to leach out of the water at about 160deg F. Most
marine motors, especially diesel ones, want to run up around 180-190deg F. If you try and use salt water as a coolant at that temp the water channels inside the motor will eventually get clogged with salt/mineral deposits. The other choice is to run the motor at a lower temp, but with diesels, you invite all manner of other issues related to running too cold.
There are thousands of boats that are sailed in fresh water and are using raw water as a coolant without problems, except one: You will not be able to add any anti-freeze to your block, which these days has lots of other good additives that help keep things lubricated etc inside the water jacket of the motor. Not to mention what happens if you live in a cold climate.
Doug

[rwidman]

Checking an engine thermostat is about as simple as it gets. Take it out of the engine and put it in a pot of water on a stove. Heat the water and using a thermometer, measure the temperature of the water. You will see it begin to open. Check the temperature of the water to see if it is opening at the correct temperature.


With a boat that you didn't buy new and service yourself, you have no way of knowing if the thermostat you have is the correct one for your engine. A raw water cooled engine should run at about 150 degrees F. A fresh water cooled engine should run at about 180 degrees F.

[pbmaise]

Your questions prompted me to look closely at my thermostat. It is stamped 76.5 C.

Now I have to debate whether to replace it with same or go up to the 82 C one.

Since I have a fresh water cooled engine I am leaning towards going up.

I did some google searching on the 76.5 C thermostat and car companies have termed it the "tropical" thermostat.

On the one hand I like the idea of lower temperature radiator fluids going to my heat exchanger.

On the other hand that higher operating temperature is supposedly where the engine is more efficient.

If it is more efficient, then the total BTU load on heat exchanger should be lower.

Consider to achieve the higher operating temperature means lower flow rate of coolant to engine block. So while it may be hotter, the flow is lower.

Unless I am missing something I think the proper thermostat should be the 82 C one as written in the Isuzu manual.

[pbmaise]

If you want a good laugh, I found an article guiding people to drill holes in 82 C thermostats so the engine would running cooler.

https://www.tsikot.com/forums/engine...rmostat-84258/

Here in Philippines the thermostat is being seen as the reason engines overheat instead of a device to keep engine at proper temperature.