Hi all,

This is my first post and hopefully you'll bear with me for a slightly long story. For about 6 months our 2007 diesel auto has used some coolant, about 1 litre over perhaps 5000 miles. The coolant remained clean, although I probably didn't look that closely. In the last 2 months though it has used about 1 litre a month approx 1000 miles but the coolant has a dirty look to it and a black scrum is lining the sides of the expansion tank.

Coincidentally a few weeks ago I broke down. Whilst driving at around 50mph a horrendous clatter came from the engine so I pulled into a layby and switched off quickly. To cut a long story short, a piece of swirl flap had broken,rattled through the engine and stuck open the EGR valve! This made the engine difficult to start and gave the reduced engine performance message. Anyway our local brilliant mechanic removed the offending plastic from the EGR and as a precaution removed all the swirl flaps and put it back together. Luckily no engine damage seems to have occurred and the car is running fine, mileage is 93K.

Whilst the EGR cooler was off I filled the coolant part with water, plugged the outlets and waited to see if there was a leak. No leak was found. When everything was back together a pressure test at 15psi was still held after an hour.

Now (at long last I expect you're saying) the crux :

The coolant,if it's not leaking externally, is disappearing via one of the following, the EGR, the oil cooler, the transmission fluid cooler, the head gasket or via a porous head/block.

The gearbox is changing gear as well as ever so I don't think the transmission fluid cooler is the cause and the deposits are black rather than reddish. Issues with the head, gasket and block seem unlikely. If the oil cooler was leaking I'd expect to see more deposits in the coolant and the level to increase due to oil pressure pressurising the coolant. The oil was changed recently and didn't appear to have any contamination I.e. no mayonnaise.

I'm tending towards thinking it's the EGR cooler/valve but it would be interesting to hear other members opinions before I commit a few hundred pounds on replacing the EGR cooler/valve.

Get your mechanic to do a gas test to see if there are any combustion gases in the coolant and work back from there. You may well be on the right track Td4 XS manual, Orkney Grey, MY2014

As your car is before MY2010, before changing EGR, plug it at exhaust manifold place - there will be no error on the ECU because of the "abnormal" gases' flow -, leave it in position with the electrical connector in place in order to seem all OK to the ECU and "short circuit" the EGR cooling hoses in order for the coolant to not pass anymore through it.
See if the coolant is remaining stable.

Thanks for the replies,

Hi DAC364, my mechanic doesn't have a gas test kit but I could buy one myself for about £40 which compared to the EGR cost is minor.

Hi Alex, bypassing the EGR would definitely isolate the cause, is the exhaust blanked before the EGR to prevent damage to the EGR assembly from uncooled exhaust? What do you think of the simpler idea of looking for combustion products in the coolant?

A picture makes a 1000 words. Below is the EGR system. You can click on the picture to enlarge it.
You can't damage the EGR if you blank the exhaust exit from the exhaust manifold.
I've pointed out with red arrow where you can blank it.
And then directly connect the hose from (5) to the hose from (7).

Click image to enlarge

I had this exact same experience in my FL1V6 and ended up being the water/oil transmission cooler. When my mechanic drained transmission fluid it was full of water, amazingly the auto trams was fine. I'd drain the AT fluid to confirm,
Doesn't hurt! MY15
Tyre Pressure Monitoring System (TPMS)
Surround Camera System
InControl Apps soon to be replaced with CarPlay (WIP)
Meridian Premium Surround Sound
Digital Audio Broadcast
Timed Climate
Cruise ECO Data
Follow Me Home Reverse
Extra Features Menu
Picture In Motion
4x4i screen (WIP)
Digital Broadcast TV
Meridian Rear Media with WIFI
Factory Powered Tailgate
Blind Spot Monitoring (BSM)
Reverse Cross Traffic Alert (RCTA)
Electrochromatic Wing Mirrors (WIP)

I made my own pressure tester with a spare coolant cap with a tyre valve fitted to the top
Bicycle pump to add 10-12 psi check with type pressure gauge then look for leaks, this method has identified leaks on various kids cars and even identified a blown head gasket on a rover k series as the air could be heard escaping through the oil filler cap.

Ok I'm going to order a combustion gas test kit. If gas is present then I'll ask my mechanic to bypass the EGR as per Alex's suggestion.

The idea that coolant could be in the transmission fluid is worrying, I could drain some fluid since I still have a litre left from when I changed it a year ago. Hopefully water would be present in the first litre drained, if it's contaminated.

The homemade pressure tester sounds like a useful thing to add to the toolkit.

Thanks for the help.

You could also bypass, for testing purposes - not permanently, the transmission oil cooler and short circuit its water connections if you think about it.
Don't worry, the transmission fluid is warming up veeeery slowly, of course, if you don't tow or climb some very steep hills. And for the peace of mind shift it in sport when you bypass the transmission oil cooler, because in sport the TCC will be locked as soon as possible eliminating in this way the unnecessary slip that will rise the transmission oil temperature.

Otherwise try and pressure check the AT oil cooler, it's easy to get to and disconnect as coolant/oil connections are right there!
I had no malfunction of the AT, it just continued uninterrupted!
Sounds identical to my experience, was a very gradual coolant drop.
Good luck  MY15
Tyre Pressure Monitoring System (TPMS)
Surround Camera System
InControl Apps soon to be replaced with CarPlay (WIP)
Meridian Premium Surround Sound
Digital Audio Broadcast
Timed Climate
Cruise ECO Data
Follow Me Home Reverse
Extra Features Menu
Picture In Motion
4x4i screen (WIP)
Digital Broadcast TV
Meridian Rear Media with WIFI
Factory Powered Tailgate
Blind Spot Monitoring (BSM)
Reverse Cross Traffic Alert (RCTA)
Electrochromatic Wing Mirrors (WIP)

Pressure tests don't always work - for example the leak may only be present when engine is hot. Just for peace of mind, with engine hot, let it idle a bit, get someone to watch the exhaust and rev the engine. If there is any WHITE smoke (actually steam) then it's head gasket or cracked head. Had several of these (last one on a TD5 - common problem), but never heard of one on this engine, so you're probably fine, but best to be sure. Ex AA Series III LWB Safari - Gone
300TDi Disco (bought new - terrible car) sent back after 18 months
Freelander 1 Estate - leased, given back at end of lease
200TDi Disco (bought from a mate with 100,000 on the clock) - Gone
Disco 2 TD5 - sold and exported to France
FR2 TD4 GS - Gone
FR2 SD4 HSE - Now changed for a DS
New model ex-demo Evoque S 180 in white
Unable to order a new DS, so gave up. Now have a Volvo S90 Recharge.

Plenty of things to try, I'll try the white smoke when hot test this weekend, I'll probably wait for the combustion gas test before trying anything else though. In any case I'll post updates when I know more, in the meantime thanks again.

Just to add to that, if you DO get white smoke out of the exhaust it will smell of anti-freeze. As I wrote before, I think it's very unlikely to be the problem on this engine, but an easy test to do. Ex AA Series III LWB Safari - Gone
300TDi Disco (bought new - terrible car) sent back after 18 months
Freelander 1 Estate - leased, given back at end of lease
200TDi Disco (bought from a mate with 100,000 on the clock) - Gone
Disco 2 TD5 - sold and exported to France
FR2 TD4 GS - Gone
FR2 SD4 HSE - Now changed for a DS
New model ex-demo Evoque S 180 in white
Unable to order a new DS, so gave up. Now have a Volvo S90 Recharge.

Thinking.....

If it was the head gasket then as combustion gasses leak at the head gasket fail point, bubbles would occur at the header tank. Equally with the engine stopped , coolant under pressure would leak into the offending cylinder and seep down into the sump. Oil floats on water. So... If you go to the sump drain plug and drain out 2 litres of oil into a clean container , then carefully pour the removed oil into another clean container any oil would be evident at the end of your pouring. If no water then it cannot be the engine or egr, so it must be the auto cooler.
.
If water is found in the oil, do a full oils change and follow Alex's egr blank and bypass before starting the engine. Do the same test a week later for water in sump oil, if no water it's the egr, if water then it's the engine.
.
Do be aware that to change the engine oil 100% is tricky because the threaded bung for the plug is higher than the bottom of the sump. The car needs to be hot, elevated at the front then use a pipe cleaner bent into a hook and threaded up the sump plug hole. It's amazing how much oil comes out by capillary action.
.
I wonder if with the engine running and the header tank cap off if you could bung a potato up the exhaust? If bubbles appeared at the header it would prove it was the engine / egr?.
.
Kind regards from Fred.
. 2010GS Auto ex Celeb, Santorini Black, 2011 facelift , spoiler, spats, mudflaps, LED footwell lamps, Witter detach,
Other cars:-
1958 & 1959 Austin J40 Pedal Cars under restoration (I make many J40 parts)
If you have an Austin J40 or Pathfinder Pedal Car looking for a new home pls PM me.
2009 Meriva

Well the oil was changed 2 weeks ago when the broken swirl flap was removed from the EGR valve and all the remaining flaps removed from the inlet manifold and there wasn't any water present then. I didn't try the pipe cleaner trick though. The potato theory is a good one, I'll try that tomorrow and report back. Leak is getting worse, took 1 litre today for 2 weeks / 500 miles which at least means it should be easier to find.