HElP NEED - Engine overheating

[RobertMartin]

I have a old Nanni 20 hp raw water diesel, which seem to be overheating. It warms up ok, but when revs are increased , the temp gauge goes as high as it can. I have cleaned out the water strainer and water flows through the seacock ok, the water is getting through, as I disconneted the pipe to check for flow, there is water coming out of the exhast, but not huge amounts. It seems to be just not ciculating through the engine... Any ideas????

 

[jfkal]

OLD seems to be the keyword. I assume it is seawater cooled as well?! What happens is, over time the internal cavities get constricted by slowly building up of deposits. This is restricting the water flow through cylinder head and along the cylinders as well. That could well mean disassembly of the engine and thorough cleaning. However before you do that get the thermostat checked it might be clogged and not opening allowing the right flow of water through the engine.

 

[vyv_cox]

I can't add to that, either the thermostat or the internal passages. You might find it successful to run the engine for some time whilst circulating fresh water, perhaps with some flushing fluid obtainable from your local car parts centre. Unfortunately, these fluids are not formulated for salt removal, so they may be only partially successful. If not then it's the mechanical methods as suggested by jfkal.

 

[longjohnsilver]

I have read of a product from Shell called Dromus B which is supposed to brek down salt deposits although I haven't used it myself. Maybe worth speaking to Shell.

 

[gunnarsilins]

Thermostate???

I´m wondering....can it really be the thermostate as mentioned here? A thermostate is basically a temperature controlled bypass valve and should not restrict the total amount of water flowing through the engine even if it´s binding. It just directs the water either way....or am I wrong?
When stating there is not too much water coming out from the exhaust I would rather think that the there are deposits restricting the flow. Not only salt, can also be rust if the engine is old and raw water cooled.

 

[Col]

As you mention poor water flow out of the exhaust,that is the first part I would check,these tend to get blocked by shale.You can check water pump and exhaust by feeing the hose coming out of thermo stat,if you can feel it" balloon" excessivelywhen revs increased, you are looking for a blockage in the exhaust,if not check pump impellors and engine cooling passages.Let us know what you find.

 

[Solwaycruiser]

Having had similar problems on two different volvo engines I found my problems both times to be a build up of hard deposits in the exhast bend/manifold where the water was introduced to the exhast system. The problem was therefore cured by chipping away these very solid deposits.

 

[johnt]

Dear oh dear ..salt is soluble in fresh water!

the deposits are LIMESCALE..and I described how to get rid of them in PBO October issue.

 

[vyv_cox]

Not always or exclusively

I deliberately did not say that fresh water either would or would not remove deposits. For instance, the "gas poker" water injector on Bukh engines frequently clogs with salt, not limescale. Washing it in fresh water will always clear it. A small passage in the cylinder head of my old Yanmar 12 used to clog frequently with a mixture of salt and carbon, again, a fresh water wash would always clear it. Sodium chloride is not highly soluble in fresh water and clearing deposits can take some time.

I didn't read your article, but it sounds as though there were some omissions and oversights.

 

[johnt]

Re: Not always or exclusively

thats what happens when half of what you write gets printed lol..

what oversights and omissions did you have in mind Vyv

and I didn't say HIGHLY soluble did I?