Logo
FULL SITE MENU

Diesel 6v92 bubbles in heat exchange unit

P

petesh

New member
I have a Chriscraft constellation 500 with twin Detroit 6V92 motors. Over the past few days I have discovered bubbles in my water heat transfer box. They are small frothy bubbles rather than big bubbles and are slowly pushing the fluid out.

I have dissolved and put seven seal lock tablets into the system. Thy are supposed to seal any leaks in the head or motor. I have then run the motor for 30 mins at 1000revs for 30 minutes, left it to cool totally. I have done this now three times but there does not appear to be any appreciable difference.

I have fitted a new recovery tank system with a further overflow tank complete with new recovery 7lb radiator cap. I burp the motor and fill the heat exchange to the top before starting. When running at 1000 revs for 30 minutes I am getting about 5 litres of fluid in the overflow tank.
The engine starts first push and does not miss, there is no apparent smoke from the exhaust on start up and the motor runs perfectly. I have used a thermo gun on both motors and there is no appreciable difference in heat between.
There was a suggestion that it could be the water pump impellor cavitating and pushing bubbles into the water. could this be the case? would the water pump cause bubbling in a fluid filled system and would this be enough to push the fluid out?
I live in a country town in Australia and not trust the local diesel mechanics in this town(I was quoted $40000 to repair the other motor when it blew a water hose which I fixed with a $5 hose - not a complete rebuild)
Can anyone offer any advice please
 
It's not the water pump. You are leaking exhaust/combustion gases into the cooling system. Seal lock Tablets will not stop this leak. May be time to tear her down and look for the leak.
 
x 2 on Chris's comments. I don't know that particular engine very well, but sounds like a blown head gasket or similar.
 
Yes, I would agree that it is probably combustion gas. I don't know about where you are but here in the states, they sell a little chemical kit that will tell you if that's what is causing the bubbles. It's not very expensive and will at least give you some information about where things might be heading to get it repaired. The link below explains:

http://www.blockchek.com/instructions.htm

If it is combustion gasses, on this engine it is more likely to be an injector tube than a seal because each cylinder has a compression gasket and the coolant flow is contained in the head by separate water jacket seals. There is no "head gasket" per se.

The other possibility is a crack in one of the fire decks of a head. The good news is that the 92 is less less likely to have this happen but it can occur.

I wish you good luck.
 
Jgmo is dead on. It could be an injector tube however it's most likely a crack in one of your heads . It's happened to me twice. Get a pressure tester or pull your exhaust manifold and look inside. I'd hold the stop button before firing them up. If coolant gets into a cylinder you'll snap a rod very easily. These marine detroits have to much horsepower. Detroit never meant for them to push out so many ponies. The cooling systems are marginal especially the oem Detroit heat exchanger. Those heads are shedding a lot of heat and are prone to cracking. What horsepower are yours? I have the Covington 550 horse models.
 
Back
Top