I have a question about a 2003 u295 with isl Cummins engine. When the engine is running there are air bubbles in the plastic coolant bottle. It looks like boiling, but engine temperature 180 it overfills the recovery tank. The radiator cap has been replaced with 2 different caps and still does it. One new cap tested at 15 pounds and the other 13 pounds. Both are new 15 pound caps. Looking for ideas of what could be the cause.
Do the bubbles get worse when you rev the engine up?
Obviously, a leak from a cylinder/head gasket would result in bubbles in the coolant.
Any "smell" or sheen to indicate combustion gasses in the cooling system?
No, have talked with a diesel mechanic and he suggested that it could also be the engine air compressor. Just wondering if there are any old truckers that ran into this over the years.
I hate to say it but usually that is an indication of a blow head gasket or engine gases getting
in to cooling system.
That is kind of what I am thinking.
What does the engine oil look like? How about the exhaust?
Been trying to help on this also
coolant is clean and so is oil... no water from exhaust either... maybe stuck thermostat or radiator?
maybe trapped bubble in the system? needs pumped out?
I've seen head gaskets gone with no smell and everything clean but the bubbles was the
giveaway. The compressor idea from red tractor could have some validity as I believe they
are water cooled. Not sure how to check it.
Just bypass the compressor, some are easier than others though. My crane has 3/4 heater hoses in and out.
Keith, yes the bubbles seem to get worse when the engine is revved up.
Use this kit or drive to a radiator shop and have them check for products of combustion in the coolant. https://www.napaonline.com/en/p/BK_7001006 Works on gas, diesel, propane, etc. I solved the problem in a 327 Chevy by just re-torquing the heads. My FD used a block sealer on one of the apparatus with a badly leaking head gasket. This was a successful application that worked exactly as advertised and lasted.
Pierce
The coach was taken to a Cummins shop and found the head gasket had blown out on #1 cylinder. The head checked ok so only needed gaskets.