TDV6 head gasket or air pockets in coolant system?

[jwaterhouse]

Hi all, long time lurker but first time poster...

My 2006 disco 3 TDV6 with 245k kms has been having coolant issues and I'm hoping someone can enlighten me as to the cause.

First noticed the low coolant warning light on my way home from work, pulled over and found a coolant leak out the top of the expansion tank. Not a lot but enough for a small pool to form under the car, passenger side right under the expansion tank.

Topped it off and got it home. Have ended up replacing the expansion tank, new genuine coolant cap and water pump in an effort to solve it, however I still get coolant overflow from the expansion tank. I've followed the official LR guide to bleed the system (twice) and the return hose flows strongly back into the tank, coolant looks a little bit airated/bubbly though. Do I just need to bleed it some more?

I'm concerned it might be a HG issue but have no other symptoms. No white smoke, exhaust smells normal, oil looks normal (no chocolate milk/mayonnaise) and importantly no overheating. Temp gauge always shows normal (about 50%) and no other warning lights. Only concern is maybe its leaking exhaust gases into the coolant system and over pressurising? Haven't been able to do a block test or pressure test yet but its booked in to the mechanic this week so will get them to check. Engine sounds a bit grumbly after a cold start but quietens down after it warms up (couple minutes), related?

Anyone run into similar issues or have any ideas what it could be? Many thanks in advance!

[DieselLSE]

Sorry jwaterhouse, but every symptom you've mentioned points to a head gasket or cracked/warped head. The good news is that your mechanic will be able to diagnose it quite quickly as there will be exhaust gasses in the coolant and/or the coolant will be being pressurised above normal. Best of luck with this.

[Tins]

Hope for the best, plan for the worst.

[justinc]

There is a minor possibility that one of the EGR coolers has failed, excessive pressure in the cooling system is not usually a symptom if that though...😮

[Dagilmo]

Hi johntins,

I had similar symptoms. Rough start and idle until warm and gas detected in the coolant. Initially, head gasket or cracked head diagnosis form Rovertech. However, with further investigation (by Rovertech) the gas in coolant turned out to be rusted and leaking EGR valves and rough idle was fixed with three new injectors.

[jwaterhouse]

Thanks for the input everyone, really appreciate the insight.

Dagilmo may be on the money. Just got off the phone with the mechanic who said he's run just about every test he can think of and believes he's narrowed it down to the EGR coolers. Asked him if he thought the head gasket was involved at all and he was adamant it wasn't.

Two new coolers are on order and should be installed next week. Expensive pieces of kit but I hear it's common they fail so was just a matter of time I guess. Will have to follow up on the injectors too.

justinc is right, it's hard to find information about EGR cooler faults manifesting as gas in the coolant system, only reference I could find here: http://diesel.org/nozzle/ford-6-0-head-gaskets-vs-egr-cooler-failure-diagnostic-question

I've had the EGRs blanked a couple years ago but seems there is no way to bypass the coolers on these engines? Or if that's even a good idea?

[BobD]

My coolers have been removed and the coolant pipes blanked off. However, the software needs to be changed and an emulator installed to allow for no valves , rather than just blanking them off.