Diesel in the Coolant !!!!

J

JWT

Member
I have a big problem - my 1.4TDI Sport has had a major rebuild of the engine since an emisions failure at its last CT (MOT).
This has incuded new big ends/rings/clutch etc etc. What was done cured the excessive fumes which was postive and the reason for doing the job.
Part of the rebuild has been a reconditioned cylinder head which was sourced in the UK form Excel Engine Services.
The car has been running - not on the road yet - but now diesel has appeared in the coolant - the thoughts are that the head may be cracked allowing the diesel and coolant to mix - has anyone experienced this before ??
 
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I'm struggling to see how you would get neat diesel in the coolant, unless it was either during the rebuild process somehow, or there was a large quantity of diesel in the cylinder AND you have a head gasket fault. You sure it's diesel? How much is there?
 
It's a new head gasket as part of the refit plus bolts etc. It certainly smells like and has the consistency of diesel - its difficult to estimate quantity as its mixed when viewed in the expansion tank.
 
I'g guess what is important is to determine whether more is getting in there. It should be floating on top of the coolant, so you could top that up with water until the diesel runs over the top then siphon out the coolant until it's back to the right level. Then run it more and see if more appears.
 
Pressure test the coolant system. The test should be over an hour or so, not a quick snap. Ideally with a hot engine.
Mac.
 
I suspect it is not a coolant issue but a problem with the "new" cylinder head. The fuel is at a very high pressure inside the fuel rail, so a small crack can easily allow the high pressure diesel into the cooling system. If it was an injector stuck open the diesel would end up in the engine oil.
 
Thought the injector body O ring seals could also be an issue but I can't find a diagram to show if the fuel could actually migrate into the cooling galleries

Cheers Spike.
 
spike said:
Thought the injector body O ring seals could also be an issue but I can't find a diagram to show if the fuel could actually migrate into the cooling galleries
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I doubt that there are any points where separation of fuel and coolant is by an O-ring; fuel and coolant should be completely separated. It does suggest that the head is cracked. It might be worth draining the coolant and refilling before you condemn the head. Is it possible that the fuel entered the cooling system during re-assembly?

RAB
 
The fuel distributor tube or fuel rail located inside the head has probably found a crack into a water cooling passage. A pressure check of the fuel in the cylinder head could reveal if it is cracked. The fuel system operates at about 160Bar so a specialist would be needed. How long ago did you get the head and is it under warranty? Would consider removing the head for either the supplying company or another specialist to inspect and test and if faulty refund or replace. Big difference between residual contamination and a defect causing a leak.


Also diesel in the coolant will start to melt the inside of all the rubber pipes so best to act sooner rather than later.
 
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