Thread: Diesel in cooling system

Had a good look and it is definitely not coming from the fuel cooler itself,they love to leak?
Usually at the hoses.

The overflow from the coolant bottle is on right side of engine around the fuel cooler area.

Although i may be thinking of the later D2,fuel cooler was a bit different on the later model,but the earlier one was still on the right side of the engine.

Originally Posted by fabdon

Hi there,

First time poster looking for some of your thoughts.

Recently purchased a discovery 2 2000 model td5, the car has a diesel leak coming from the front of the engine. I have traced it down to the cooling system reservoir over flow hose. It appears that the reservoir has a healthy amount of diesel in there.

My question is has anyone experienced this before, as I see it there are two potential possibilities

1 the diesel cooler is allowing the higher pressure fuel system to leak fuel into the water. Has anyone experienced one of these failing in this way before??

2 crack in the head allowing fuel to travel into the cooling system.

The engine starts and runs fine.

Haven't heard of this scenario before. Your 2 theories sound pretty on the money. Hope its just the fuel cooler.

Could you drain the cooling system and pull the hoses from the fuel cooler. Turn on ignition and prime fuel system to see if diesel comes out of coolant hose spigots on cooler. Won't help if only happening on expansion when hot..

Alternately could bypass fuel lines from cooler.....or..... remove fuel Ines from cooler and use cooling system pressure tester to pressurise cooling system and see if coolant comes out of fuel line fittings on cooler.

Hope this helps

Cheers, Dave.

I had diesel in coolant, initially diagnosed as fuel cooler, which was replaced, but did not fix problem and ended up with a new head. Fingers crossed it's just the cooler. Have yours pressure tested.

Can you definitely identify fuel in the coolant? The reason I ask is the fuel pressure regulator is the usual culprit for diesel leakage in that area. Are you losing coolant from the expansion tank? Hope it is something simple, Bob

Thanks for the replies,

Diesel is definantly coming from the expansion tank overflow.

i disconnected the water lines from the cooler yesterday and ran a bypass eliminating the cooler. I ran the car for a short time at idle but i am a bit reluctant to drive it without the cooler connected. I was hoping to see some fuel flow out of the cooler whilst disconnected but no such luck.

Looks like there is still diesel in the water but I can't be sure if its just residue or not without running it this way for a while.

Will I do any damage to the engine if I drive it for a few days without the fuel cooler conected?

Also looks to me like the cooling system is being pressurized but I would have expected that if the fuel is leaking in.

Almost certainly a cracked head, 3 months ago I went through exactly the same scenario posted on this site. I ended up replacing the head with an AMC Turner head from the UK. The symptoms on mine were:
1. Traces of Diesel in header tank verified by dipping a strip of newspaper in and seeing if it would burn (yes)
2. Progressive pressurising of hoses and eventual rupturing.
3. Coolant loss out of overflow.
4. Engine still ran well.
5. Luckily I was able to try another cooler at no cost to eliminate that.
I cost my self a fair bit replacing hoses and coolant until I accepted the inevitable. Now my engine runs like new and no regrets at the cost of the head.
Nick

diesel in the expansion tank is in most cases that I have seen is the cooler failing internally. (my personal belief is that this is caused by contaminants in the coolant abrading the core or in the case of higher KM engines the cooler not being replaced when the cooling system is overhauled)

there are some cases where an internal failure of the head is at fault.

Its easy to tell which is which,

Partially drain the cooling system, remove the hoses from the cooler then bypass the relay for the fuel pump and run the pump manually.

let it go for a while, if you get no diesel coming from the coolant barbs on the cooler pull the lower radiator hose, if its leaking out of there then its the head gallery.

Don't

• try to save the coolant,
• Try running the pump with less than about 3/4 of a tank of fuel

Do

• a full flush of the cooling system starting with a mild detergent to get rid of the residual diesel
• replace the FPR, cooling system cap and the hoses (remember the secret hidden one between #4+5 under the exhaust manifold)
• Drain and flush the fuel tank, when the engine is shut down hot once the fuel pressure drops off the cooling system pressure will be higher and coolant will have made its way into the tank. Diesel snot grows at the boundry of water and diesel.

Budget for

Replacing the water pump in the near future.