Thermostat and thermostat housing

[rognvald]

Originally Posted by 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.

Always use the recommended thermostat for your engine. It is designed to function for the maximum operating efficiency of your engine. Good luck and safe sailing.

[pbmaise]

I actually don't have a thermometer on board to test the thermostat. However, if I assume my guage is correct and engine normally runs at 155 F then my 76.5 C (170 F) thermostat is not working well.

I absolutely must replace the very worn gasket and suspect buying the gasket separately would be near the price of the thermostat. I find the exact 82 C thermostat for my engine on ebay for under $30. Hopefully a local supplier sells them for under $60.

[Valmika]

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.

You have a fresh water cooled system. I had an aluminum thermostat cover that did the same thing. It cost me 200 US but had a new one fabricated out of steel and never had the problem again. The extra 12 ounces may have slowed me down a bit but I'm not too concerned.

[Barney21]

I agree with the comment about welding to cast, it does not work.
Dont do the plastic buildup thing unless you have no option.
Take the housing down to your local plumbers supply, scratch around in the brass pipe fittings . Find a Brass / Bronz reducer with the same diameter as your thermostat housing, have a guy with a lathe machine the mating surface to fit the head , now you can grow whatever hoses you need off the top in brass, will probably last longer than the engine. And be 1/3 the price of anything marked "Marine Use".
I have used this method and it works better than original .

[pbmaise]

Originally Posted by Barney21

I agree with the comment about welding to cast, it does not work.
Dont do the plastic buildup thing unless you have no option.
Take the housing down to your local plumbers supply, scratch around in the brass pipe fittings . Find a Brass / Bronz reducer with the same diameter as your thermostat housing, have a guy with a lathe machine the mating surface to fit the head , now you can grow whatever hoses you need off the top in brass, will probably last longer than the engine. And be 1/3 the price of anything marked "Marine Use".
I have used this method and it works better than original .

I have been using the wrong term. It is the Thermostat COVER which has a two inch hose connection which in turn bolts to the Thermostat Housing.

The cover is bolted in six places and four bolts are very long because they go through the housing.

The thermostat housing appears to be made from aluminum too. It has several connections including a temperature sensor.

There is a connection of concern. A smaller line about 3/4 inches also appears to have some corrosion so now I am debating removing the housing.

However, likely I would need a new gasket if I do to out it back on. That gasket I want to confirm availability first.

I may end up using a high temp sealant in case this line has corrosion on it.

[Barney21]

Originally Posted by Barney21

I agree with the comment about welding to cast, it does not work.
Dont do the plastic buildup thing unless you have no option.
Take the housing down to your local plumbers supply, scratch around in the brass pipe fittings . Find a Brass / Bronz reducer with the same diameter as your thermostat housing, have a guy with a lathe machine the mating surface to fit the head , now you can grow whatever hoses you need off the top in brass, will probably last longer than the engine. And be 1/3 the price of anything marked "Marine Use".
I have used this method and it works better than original .

Sorry but forgot to mention you obviously just drill some holes in the brass reducer drill some brass rod to suit original bolts fit those into the holes made in the reducer and braze the tubes in place. If you want "
bling" polish the brass. It will give you something to do when the wind stops!

,

[pbmaise]

Originally Posted by Barney21

Sorry but forgot to mention you obviously just drill some holes in the brass reducer drill some brass rod to suit original bolts fit those into the holes made in the reducer and braze the tubes in place. If you want "
bling" polish the brass. It will give you something to do when the wind stops!

,

Barney the part with the aluminum corrosion is actually the thermostat cover. The flange surface is 3.25 inches in diameter. That flange is held in place by six bolts. Four bolts are very long and go through the thermostat housing.

The housing does have a much smaller water port which appears to be a bypass that could be changed out because it screws into housing. This bypass does not go into the heat exchanger.

Owing to custom nature of cover it looks like repairing the area is best.

I have several options

#1 Machine new coverplate from billet.

#2 Clean, prime etch epoxy, build up with glass epoxy.

#2a Build up with aluminum filled epoxy or JB Weld.

#2b Attach hose then back fill with Permatex Form A Gasket

#2b-1 Hard setting Permetex

#2b-2 Non-hardening

#3 Machine shop attempt to build up area with aluminum

[Barney21]

I was aware it was the thermostat cover.

Ok you need to get to a Plumbing supply outlet and buy a 3 1/2 " reducer, made of Bronze/Brass with a female thread in both ends the reduced end to fit your radiator hose ,maybe 2" . When you have that take it to your machine shop and match the fixing bolts holes, this will require brazing some solid bar onto the reducer, then drill the bar to suit your fixing bolts. Any other "take off" fittings will be attached to the 2" hose barb you are fitting.
All this is assuming you cant get a new Thermostat housing for a Isuzu BD engine , which I would find difficult to believe, there were millions of these engines in Trucks world wide, but it depends where you are.
Just dont try and weld to crystallizing aluminum.
You could cut a ring off the original of say 1/4" and make up a new 1/4" ring and have that welded, I would be getting it replaced with a new one first opportunity