Fountaining header tank

[ditchcrawler]

The new pressure tank is about 2 pts.

 

The Bukh workshop manual says 4lb header tank top pressure (and specifies a certain Delco pressure cap). However, my mechanic says that this is unnecessary and that with the hydrostatic pressure from a header tank about 9" above the water jacket things are about right.

4 psi = about 9 feet not inches water gauge

Edited March 27, 2010 by ditchcrawler

[ditchcrawler]

After all that, water persisted in the lubricating oil. So the engine had to come out. The double O ring system at the bottom of the wet liners of both cylinders was flattened, presumably from heat damage, thus allowing coolant to leak into the sump. I took the opportunity to replace the crankshaft shells, which showed early wear, and to renew all gaskets. Cost of parts £900, I await Blackhand's bill.

Insuficent pressuer of the cooling system can allow local hot spots to boil and then you have steam,not water which could lead to local heat damage.

[Giggetty]

My Bukh 20hp diesel has always overheated at provocation-rope round prop, etc. So when the skin tank sprang a leak at the base I took the opportunty to have welded in a new section (with internal baffle). This increased the surface area from 4.175 to 5 sq ft. At the same time I flushed the coolant circuit, replaced the impeller and changed the antifreeze.

 

Imagine my chagrin. After all this when taking it out there was again overheating. This was after only 1mile 5 furlongs at 3000 rpm (full grunt) continuous.

 

No rope round prop this time

Fabricator stated skin tank internally OK on inspection

Normal coolant level in header tank (unpressurised system), 50% MEG/IDT (Blue Star)/rainwater 49l total). Tech specs say this mixture has unchanged specific heat vs pure water

Thermostat opens at ~65 deg C

Oil OK

Water pump OK as judged by header tank input

No problems starting, exhaust colourless.

No airlocks (airbleed screw in skin tank)

No oil in coolant or water in oil

 

I'm running out of ideas

Edited October 8, 2013 by Giggetty

[smileypete]

Try to get an IR thermometer to check the temp. drop across the tank, failing that a Mk1 hand.

 

If it's hot going in and cool going out, while the engine is overheating, it's likely to be a flow problem, thermostat not fully opening, problem with pump, kinked hose, airlock etc.

 

If it's more or less equally hot both ends then the tank isn't rejecting heat fast enough from the engine, could be too much thickness of hull coatings and/or foulings on the outside, maybe a slim chance the engine is really out of tune.

 

Basically first the heat has to get into the tank fast enough, then be rejected out though the side of the skin tank fast enough

 

cheers, Pete.

~smpt~

[Bod]

Have you got all the old impeller bits out?

None left lurking, blocking the water flow?

 

Bod