Thread: 2005 D3 TDV6 loosing coolant on long trips

I'd be removing the radiator and having it thoroughly cleaned. Cross flow radiators are notorious for blocking the lower approx 3rd of the radiator. The fact that it tends to only happen on longish trips tends to back this up as short trips would not get the entire cooling system up to its normal running temp for long enough periods and the cleanish 2/3rds section would handle the cooling reasonably well. You haven't mentioned vehicle klms however if they are "up" then the radiator would be due for a thorough clean out.

While reading your enquiry it reminded me quite quickly of a similar problem I had including all the possibilities, tests, checks , replacement radiator & expansion tank cap & the problem remained. My car was fine unloaded but after a couple of hours driving with the caravan attached I could smell coolant & sure enough when I stopped & checked there was expelled coolant around the top of the expansion tank & flowing down from there. I was suspicious as each time I checked & topped up the coolant the cap was slightly loose leading to replacing a couple of caps.

A suggestion from MR Automotive at Redcliffe in Queensland led me to resolution of the problem. I had previously fitted an aftermarket coolant tank due to a faulty temperature sensor.
They pointed out that they had the experience once of this same problem & traced it back to the expansion tank they had fitted, and no longer use. It seems that the economically priced tank was made of a plastic material that would lose it's shape or shrink or not expand at the same rate as the cap, whichever cap was used. When this occurred the cap would loosen slightly & allow coolant to escape.
Rather than replace the motor, which I was about to do, I replaced the expansion tank with a quality OE equivalent tank, Mahle in this case, and my problem was resolved.
I took the car with caravan on for a drive as hard as I could up the Dorrigo mountain & beyond to test it & was relieved to find no coolant leaks, but still guarded regarding success.
I have since done a few trips with the van on including recently out to Birdsville/ Bedourie etc & have not had any problem whatsoever with the coolant system or anything else.

My suggestion from what you have described would be to replace the expansion tank & cap with good quality items before spending any more big money on many of the good suggestions that people have made.

Thanks immensely MR Automotive.

Regards,
Wayne. Retired & tired mechanic that still does no know it all .

Originally Posted by Journeytower

due to a faulty temperature sensor.

Faulty level sensor I believe

Originally Posted by Journeytower

My suggestion from what you have described would be to replace the expansion tank & cap with good quality items before spending any more big money on many of the good suggestions that people have made.

+1 to that. We had a replacement fitted after the level sensor failed and it took 4 return visits to diagnose a duff coolant bottle. Replaced with a quality part and it hasn't been an issue since.

Looked fine and held a static pressure test, but when hot it sprayed a fine jet of coolant out that got entrained in the air through the fan, spraying it over the front of the motor making it look like the leak was somewhere expensive.

MR auto replace the coolant reservoir and float assembly every time they do a coolant flush,and the plastic piece on the engine,using only OEM parts.

Cheap compared to continual issues that can result in engine damage.