Repeat Coolant O-Ring Failure

Mekanik · September 28, 2010

Okay diesel gods, we’ve got a weird one in the shop. We've got a 2005 F450 with a 6.0L that has a coolant leak from the big O-ring that goes between the intake and front cover. About 4,000 miles ago we replaced the EGR and oil coolers in the truck because it had a leaking EGR cooler. The front cover gasket was replaced two weeks before the EGR/oil cooler repair at a different dealer, and supposedly the engine was overheated. When the tech took the engine apart to replace the coolers, he noticed that the big O-ring was all chewed up on the inside part of the O-ring. We thought this was weird because the part is only two weeks old.

Well here we are again. The truck has an external leak from the O-ring. It is chewed up on the inside again and is now split too.

Has anyone run into this, or have any recommendations?

Keith Browning · September 28, 2010

Is there any evidence of fuel or oil contamination of the engine coolant?

Mekanik · September 28, 2010

No coolant contamination.

GregKneupper · September 29, 2010

The only time I have seen that is when the coolant had diesel fuel in it.

Bruce Amacker · September 29, 2010

The only time I have seen that is when the coolant had diesel fuel in it.

Ditto. Check it again for fuel contamination.

Good Luck!

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Mekanik · September 29, 2010

Really? It looks as if someone has been cutting at the center of that O-ring with a razor.

Bruce Amacker · September 29, 2010

That's exactly how it will look when fuel has entered the coolant. The o-ring in question is rubber, not neoprene, and has zero tolerance for petroleum substances.

Most o-rings are neoprene, Viton, or another oil-resistant material. Rubber (a common rubber is EPDM, used in coolant hoses) is visually identical to neoprene but degrades in the presence of oil very quickly, usually within hours. Try putting one end of a piece of heater hose into a pan of diesel fuel overnight- it will swell up 2-3 times it's original size where the diesel fuel is absorbed.

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Keith Browning · September 29, 2010

Well the reply I scratched out was quite dummed down from Mr Amackers post... which I also believe is the answer to your dilemma.

mchan68 · September 29, 2010

That's exactly how it will look when fuel has entered the coolant. The o-ring in question is rubber, not neoprene, and has zero tolerance for petroleum substances.

Most o-rings are neoprene, Viton, or another oil-resistant material. Rubber (a common rubber is EPDM, used in coolant hoses) is visually identical to neoprene but degrades in the presence of oil very quickly, usually within hours. Try putting one end of a piece of heater hose into a pan of diesel fuel overnight- it will swell up 2-3 times it's original size where the diesel fuel is absorbed.

....which is also why I always quote EVERY rubber hose that coolant passes through whenever any vehicle comes in with oil into coolant contamination. Most of these rubber gaskets don't like varosol as well. How many times do you notice old rubber gaskets swelling up to almost twice its size, when it's been left in the varosol tank?

Brad Clayton · September 30, 2010

Quote:

fuel has entered the coolant

I don't recall seeing a F-Series with fuel in the coolant, only E-Series. How many you fellas seen?

Keith Browning · September 30, 2010

I think we have had three F-Series and no E-Series. There was a time a year to two years ago it seemed "we" saw some cylinder heads being replaced for this. I know I read of several besides the one's we saw.

Jeff_ · September 30, 2010

I've had one F series 6.0 for this that got new heads, and a bunch of 7.3's which got new cups.

GregKneupper · October 1, 2010

I have seen at least 7 f series with fuel in the coolant but have never seen an e series.

Mekanik · October 2, 2010

Thanks for the input, I let the tech working on the truck know this info. Our manager just wanted to service part the O-ring and get the truck back on the road, but I'm sure it will be returning soon enough.