T6 150 - Coolant leak & Block test.

[seismic22]

Hi all,

My T6 150 is losing coolant. I have read all the threads on here and had two garages (one specialist) look at it but I have not been able to diagnose the cause and decide what the next steps are in solving the issue. The van has 107k on it and drives fine but loses approximately 500ml of coolant in 700 miles (min to max on the expansion tank). Its been doing this pretty much since I bought the van 9,000 miles ago. The van has no history of an egr/cooler replacement. No abnormal mayo around the oil filler cap. For a long time the expansion tank did seem to be pressurised even when the engine was cold but having changed the cap it seems to be slightly better now. I have undertaken a block test myself to see if there are hydrocarbons in the coolant but whilst the colour of the liquid changed it was only ever so slightly and therefore I am still struggling to conclude whether I have an EGR or Head issue..pictures of the block test below.

What do people think of the test results below in the pictures (2nd/3rd images are after a 15 min idle)? One of the garages pressure tested the system and said it was fine. What other ways are there to help me diagnose the issue? I am obviously hoping its the EGR but I really dont want to just go throwing money and replacing bits that may not be the problem.

Any help appreicated. Thanks.

 

[seismic22]

Anyone?

 

[DXX]

You could fit EGR pipe blanking plates on both pipes, you’d want to fit them at the exhaust manifold joint and the cylinder head joint to ensure the EGR does not get hot enough to generate steam from any leaked coolant.
The engine will operate with a low EGR flow fault code because of the blanking.
If the EGR is leaking coolant will accumulate in the EGR and not be ingested through the engine, after a few hundred miles it should show when you open up the lowest EGR pipe flange.

If no leakage from the EGR you could replace it anyway.
At 107K miles it would be in very poor condition, even if it’s the second one it won’t be in great condition.

Other than that you would probably need to strip the engine to check the head gasket and mating faces with a straight edge / feeler gauges. If head gasket sealing is good; dip the head to strip carbon and oil and then use dye penetrant crack detection.

 

[T6 Pilot]

Thread '2.0 Engine coolant leaks no visible coolant loss'

13 Aug 2025

Guys I've just carried out a repair to a van been loosing coolant for a while now. All tje info is in the video. I came across this tech bulletin online not sure if any of you were aware of this do thought id share it.

• T6 Pilot
• Replies: 0
• Forum: Engine, Gearbox, Exhaust, Drivetrain

• 

 

[T6 Pilot]

Just posted this today mate the service bulletin is worth a read

 

[Dellmassive]

Hi all,

My T6 150 is losing coolant. I have read all the threads on here and had two garages (one specialist) look at it but I have not been able to diagnose the cause and decide what the next steps are in solving the issue. The van has 107k on it and drives fine but loses approximately 500ml of coolant in 700 miles (min to max on the expansion tank). Its been doing this pretty much since I bought the van 9,000 miles ago. The van has no history of an egr/cooler replacement. No abnormal mayo around the oil filler cap. For a long time the expansion tank did seem to be pressurised even when the engine was cold but having changed the cap it seems to be slightly better now. I have undertaken a block test myself to see if there are hydrocarbons in the coolant but whilst the colour of the liquid changed it was only ever so slightly and therefore I am still struggling to conclude whether I have an EGR or Head issue..pictures of the block test below.

What do people think of the test results below in the pictures (2nd/3rd images are after a 15 min idle)? One of the garages pressure tested the system and said it was fine. What other ways are there to help me diagnose the issue? I am obviously hoping its the EGR but I really dont want to just go throwing money and replacing bits that may not be the problem.

Any help appreicated. Thanks.


View attachment 299096

View attachment 299097
View attachment 299098

most likely the EGR cooler leaking.

a very common job an the T6 across all the engine variants.


compare your coolant loss to mine on our CFCA engine.

Post in thread 'Dellmassive`s Camper Van Adventure'

19 Jul 2025

Loosing Coolant . . . . . !!!

did i mention, that after the Euro trip the low-coolant light com on. . .,

that's odd i thought, so i topped it up and carried on.

well imaging my surprise when a tank of diesel latter the same thing happened.

couldn't see a leak,
couldn't small a leak (coolant leak has a very distinctive sweet smell.

my instant gut feeling - EGR COOLER.

the van is still under ALL-IN warranty, so i started making my case & building evidence.


T6Forum - window sticker (reverse) in the sun


View attachment 290539


oooosh.

View attachment 290542






here you can see the...

• Dellmassive

• 

.

 

[seismic22]

You could fit EGR pipe blanking plates on both pipes, you’d want to fit them at the exhaust manifold joint and the cylinder head joint to ensure the EGR does not get hot enough to generate steam from any leaked coolant.
The engine will operate with a low EGR flow fault code because of the blanking.
If the EGR is leaking coolant will accumulate in the EGR and not be ingested through the engine, after a few hundred miles it should show when you open up the lowest EGR pipe flange.

If no leakage from the EGR you could replace it anyway.
At 107K miles it would be in very poor condition, even if it’s the second one it won’t be in great condition.

Other than that you would probably need to strip the engine to check the head gasket and mating faces with a straight edge / feeler gauges. If head gasket sealing is good; dip the head to strip carbon and oil and then use dye penetrant crack detection.

Thank you for this suggestion

Just posted this today mate the service bulletin is worth a read

Interesting, thanks

most likely the EGR cooler leaking.

a very common job an the T6 across all the engine variants.


compare your coolant loss to mine on our CFCA engine.

Post in thread 'Dellmassive`s Camper Van Adventure'

19 Jul 2025

Loosing Coolant . . . . . !!!

did i mention, that after the Euro trip the low-coolant light com on. . .,

that's odd i thought, so i topped it up and carried on.

well imaging my surprise when a tank of diesel latter the same thing happened.

couldn't see a leak,
couldn't small a leak (coolant leak has a very distinctive sweet smell.

my instant gut feeling - EGR COOLER.

the van is still under ALL-IN warranty, so i started making my case & building evidence.


T6Forum - window sticker (reverse) in the sun


View attachment 290539


oooosh.

View attachment 290542






here you can see the...

• Dellmassive

• 

.

I have seen the thread concerning yours and it helped give me a little more confidence that it might be more likely to the the egr than anything more sinister... Thanks for your thoughts.

 

[DXX]

Thank you for this suggestion


Interesting, thanks


I have seen the thread concerning yours and it helped give me a little more confidence that it might be more likely to the the egr than anything more sinister... Thanks for your thoughts.

Don’t hang about, vapourising coolant through your engine, turbocharger and DPF is doing ongoing damage.

 

[seismic22]

Is

Don’t hang about, vapourising coolant through your engine, turbocharger and DPF is doing ongoing damage.

Do you know if there is the possibility of leaving the egr in place but disconnecting then inlet and outlet coolant pipes and connecting them together, blanking the egr and mapping it out of the ECU whilst leaving the actually unit installed?

 

[DXX]

Is

Do you know if there is the possibility of leaving the egr in place but disconnecting then inlet and outlet coolant pipes and connecting them together, blanking the egr and mapping it out of the ECU whilst leaving the actually unit installed?

If you can’t guarantee the EGR valve is closed and sealed it would overheat and almost certainly be damaged through buckling. Buckling would almost certainly increase the coolant leakage and risk a hydro-locked cylinder which is big £.
There are companies that offer an EGR ‘delete’. This is not a UK road legal option.
In that case you may as well just replace the EGR unit, EGRs should be regarded as consumables like brakes, clutches and batteries.

 

[Camper_Chris]

Check the cap on the expansion tank, i had one on a VW that had similar symptoms, I chased: headgasket, coolant system leaks and EGR. Turned out to be a £12 expansion tank cap was leaking/not holding pressure.