Diesel in coolant - cause?

[towe0609]

Had a hole in top radiator hose (99 td5 defender), spotted coolant dripping after a short run, drove straight to nearby 4wd specialist mechanic. Found small hole at join.

Mechanic sources top radiator hose from stealer, and replaces same day. parts + 1/2 hour labour charged.

10 days later, I smell coolant, and look over and see coolant spraying out from under bonnet. Pull over, immediately check temp guage still just left of centre as normal.

Another small hole in top radiator hose, different location, but also in a 'join'.

Get towed to Independent land rover specialist.

Mechanic amazed at amount of diesel in coolant, asks if other mechanic checked coolant. I don't know, but obviously not. Asks politely if I've done something stupid like put diesel in expansion tank (btw no, I hadn't). Final diagnosis, diesel leaking from fuel side to coolant side in fuel cooler/heat exchanger.

After multiple flushes, fuel cooler replaced with reco unit, all hoses replaced, parts (ouch) + 3 hours labour. Returned suggesting all working as it should.

Less than a week later after a 10km run, I return to car and notice slick in water on ground (after rain). Inspect, can't see any leak, a bit wet around expansion tank cap. Drive home with eyes glued to temp guage which doesn't move from normal position.

Leave to cool for a bit, open expansion tank, use syringe to drain from top. Darkish brown liquid - smells like diesel. Get hose, siphon over a litre of what I assume is diesel from top of tank. Diesel sitting on top of coolant - if you stick the hose down lower you can find bright red coolant.

Vehicle will be delivered back to Independent Land Rover Mechanic Monday.
So assuming they didn't get the fuel coolers mixed up, and put back on the one that was faulty, what else could be going on here?

[goingbush]

How many klms has the truck done ?
If diesel was still in the cooling system I'd have thought it would emulsify.

I'd try filling it up with water & adding some solubile oil to help the emulsification, overflow it with the engine running to 'bleed' any left over fuel out at the highest point. might need to flush a few times, test run using water, dont waste any more glycol until you know its good.

[towe0609]

How many klms has the truck done ?


35,000km - yep that's all.


If diesel was still in the cooling system I'd have thought it would emulsify.

I'd try filling it up with water & adding some solubile oil to help the emulsification, overflow it with the engine running to 'bleed' any left over fuel out at the highest point. might need to flush a few times, test run using water, dont waste any more glycol until you know its good.

The cooling system was flushed numerous times before refit of fuel cooler and replacement of hoses. I don't think the issue is 'left over' diesel - I think the issue is diesel still making its way to the cooling system somehow.

[Blknight.aus]

assuming its the td5, its a fracture in the cooling jacked of the fuel cooler.

[towe0609]

assuming its the td5, its a fracture in the cooling jacked of the fuel cooler.

But the fuel cooler was replaced with reco unit. What is the likihood of same fault again, and what would cause it? I thought heat exchangers were generally simple devices with no moving parts.

Assuming the reco unit was sound, all I can think of that somehow they got them mixed up and put the 'leaking' one back on?????

[Blknight.aus]

OR they never fully flushed out the cooling system.

getting a full flush on a td5 is a cast Iron bitch of a job, to di it properly I pull all the hoses and flush every sub assembly seperately theres a lot of nooks and crannies that contaminant can collect.

disregard, if its filling with diesel you want it to be a mechanics stuff up and theyve put the same fuel cooler back on...

if its not it will be an internal head stress or construction failure.

if it turns out that you have had the luck of 2 failed items in a row at least you'll be entitled to a freebie. you may have to pay labour if you provided the parts. The unwanted down time and extra labour usually makes buying genuine first off a much better proposition.

as to what causes is.. **** poor quality control.

[uninformed]

on another note......never trust the LR oem temp gauge....they will only let you know what you have already figured out 10min before it tells you.

[Sitec]

If the fuel cooler HAS been replaced, and you HAVE flushed the system, the only thing left that I can think of (having had the head off mine and seen inside most of it) is that the early 99 to 01 engines have the fuel running thru the head supplying the injectors internally... If one of these drillings has gone porus that would also cause the same problem you are describing... Just an idea.. Prob not one you want to have to look into. Good luck!

[towe0609]

Well the answer was both a buggered fuel cooler, and a buggered head. Yey.