Coolant leak - Investigation ideas

[Crippso]

Hi all
I recently bought a 2016 61k miles T6 campervan (ad blue). Private sell. Runs well but the coolant light came on after a couple of weeks. Topped up and found the level had dropped again after a couple more weeks. I think I lost about 200ml over 250 miles. Then again I added a similar amount after another 250 miles. I checked with previous owner and they hadn't been needing to top up the coolant (which I believe as I know the seller). So probably a recent issue. Oil level a little high but oil looks black on dipstick. Some emulsified oil at filler cap/in tube but seen similar on other VWs of that age/miles.

Its in at a local garage now for investigation. Mechanic suspects EGR based on reading up on similar issues but is trying to prove that before moving to replace it.

He's not found signs of a leak. The only sign I spotted was coolant running down the tube at the base of the expansion tank. I optimistically thought it could be a simple leak causing that. But the mechanic showed me the over pressure relief hole near the threads for the cap. He suspects that either it's overpressurising and leaking out as a result. Or that perhaps I was just a bit sloppy filling up the coolant.

Anyhow I wondered if anyone on here has any experience of this issue and any helpful advice they might be able to share. I have read on some forums that it can be possible to analyse samples of the oil and coolant to look for signs of mixing. I mentioned it to the mechanic and he doesn't have any experience of this. He's said if I can tell him what samples to take (and under what conditions, engine cold/hot etc) then he can do that. But I'd then need to send them somewhere for analysis. If anyone has any guidance on that it would be really appreciated.

Many Thanks
Stuart

 

[Broadside]

I’ll be interested to see what pops up on this thread. My van has a slow coolant leak, most recent EGR was replaced 3000 miles ago which seemed to sort it but I’ve noticed the level dropping again.

200ml in 250 miles sounds like quite a lot, sometimes my van would lose that much and then go for 1000 miles and lose none. I’m still scratching my head trying to work out what to do. Best of luck with yours.

 

[BIgben]

Hi all
I recently bought a 2016 61k miles T6 campervan (ad blue). Private sell. Runs well but the coolant light came on after a couple of weeks. Topped up and found the level had dropped again after a couple more weeks. I think I lost about 200ml over 250 miles. Then again I added a similar amount after another 250 miles. I checked with previous owner and they hadn't been needing to top up the coolant (which I believe as I know the seller). So probably a recent issue. Oil level a little high but oil looks black on dipstick. Some emulsified oil at filler cap/in tube but seen similar on other VWs of that age/miles.

Its in at a local garage now for investigation. Mechanic suspects EGR based on reading up on similar issues but is trying to prove that before moving to replace it.

He's not found signs of a leak. The only sign I spotted was coolant running down the tube at the base of the expansion tank. I optimistically thought it could be a simple leak causing that. But the mechanic showed me the over pressure relief hole near the threads for the cap. He suspects that either it's overpressurising and leaking out as a result. Or that perhaps I was just a bit sloppy filling up the coolant.

Anyhow I wondered if anyone on here has any experience of this issue and any helpful advice they might be able to share. I have read on some forums that it can be possible to analyse samples of the oil and coolant to look for signs of mixing. I mentioned it to the mechanic and he doesn't have any experience of this. He's said if I can tell him what samples to take (and under what conditions, engine cold/hot etc) then he can do that. But I'd then need to send them somewhere for analysis. If anyone has any guidance on that it would be really appreciated.

Many Thanks
Stuart

Is it a biturbo? 204ps?

 

[DXX]

If you have 61K miles on the same EGR it’s pretty much fouled with carbon anyway.
I’d bite the bullet and renew it before it gets worse and potentially causes a hydro-locked engine and bent connecting rod.

 

[JLDD]

Had my EGR replaced last year on warranty ( VW approved used AND I paid for the “All-in” Service Plan).
The symptoms described here sound almost exactly the same as mine pre-EGR replacement, except mine had the added bonus of the adblue range changing randomly as well while driving through France. Not fun.

 

[BIgben]

Had my EGR replaced last year on warranty ( VW approved used AND I paid for the “All-in” Service Plan).
The symptoms described here sound almost exactly the same as mine pre-EGR replacement, except mine had the added bonus of the adblue range changing randomly as well while driving through France. Not fun.

Sounds the same as my old 2016 204ps biturbo.
Was mysteriously losing water, they changed the egr after a lot of grumbling.
Still lost water and they then changed the cylinder head, and the glow plugs. They then couldn’t get it to start, so changed the injectors.
After getting it back for 2 weeks the turbo failed.

 

[Crippso]

Is it a biturbo? 204ps?

I don't think so. 110kW I believe. So about 150ps ish

 

[Crippso]

Sounds the same as my old 2016 204ps biturbo.
Was mysteriously losing water, they changed the egr after a lot of grumbling.
Still lost water and they then changed the cylinder head, and the glow plugs. They then couldn’t get it to start, so changed the injectors.
After getting it back for 2 weeks the turbo failed.

Ouch!

 

[BIgben]

Ouch!

Yep. It was painful.
Hence this time I’ve gone for the 150ps.

 

[RobertO2023]

Coolant loss can be tricky to identify but using a process of elimination you will find the issue
Check for any excess creamy sludge under oil filler cap
A through visual inspection with the under tray removed may be a leak from a hose or water pump
Look for dampness under the heater - less likely but worth checking
Pressure test the cooling system from cold and at normal operating temperature is the pressure steady or dropping
Use a Block Test to determine if hydrocarbons are present in the coolant points to EGR or cylinder head
Check if any pressure remains in the system when the engine is cold. - points towards cylinder head gasket or crack
Bypass the coolant hoses from the EGR and pressure test if pressure is steady - points towards EGR
My experience is that the level of coolant loss you are experiencing needs speedy attention to avoid more serious problems
Good Luck

 

[DXX]

I’ve proven coolant leaks through the engine by holding a clean sheet of paper very close to the exhaust open end for approx’ one minute.
Obviously combustion produces water so the paper will get damp but the smell of coolant (glycol) is of often traceable with a sensitive hooter.

 

[Crippso]

Coolant loss can be tricky to identify but using a process of elimination you will find the issue
Check for any excess creamy sludge under oil filler cap
A through visual inspection with the under tray removed may be a leak from a hose or water pump
Look for dampness under the heater - less likely but worth checking
Pressure test the cooling system from cold and at normal operating temperature is the pressure steady or dropping
Use a Block Test to determine if hydrocarbons are present in the coolant points to EGR or cylinder head
Check if any pressure remains in the system when the engine is cold. - points towards cylinder head gasket or crack
Bypass the coolant hoses from the EGR and pressure test if pressure is steady - points towards EGR
My experience is that the level of coolant loss you are experiencing needs speedy attention to avoid more serious problems
Good Luck

Thank you. Very helpful. I'll share that with the mechanic. What's a block test by the way?

 

[DXX]

If the mechanic hasn’t already checked the coolant for hydrocarbons I suggest you find a different garage, absolute basics for coolant loss diagnosis.

 

[RobertO2023]

Thank you. Very helpful. I'll share that with the mechanic. What's a block test by the way?

“Block Test” is a chemical mixture put into the coolant which basically changes colour if hydro carbons are present - most decent garages have will the kit

 

[Crippso]

So I've got the van back now to monitor coolant and oil levels for a few weeks. No pressure loss after 15psi pressure test (after 1hr). Cap on the expansion tank replaced. I'd seen coolant leaking down the pipe at the bottom of the tank. And the mechanic noticed it was always wet in the area under the cap where the weep hole is. Fingers crossed.

 

[DXX]

So I've got the van back now to monitor coolant and oil levels for a few weeks. No pressure loss after 15psi pressure test (after 1hr). Cap on the expansion tank replaced. I'd seen coolant leaking down the pipe at the bottom of the tank. And the mechanic noticed it was always wet in the area under the cap where the weep hole is. Fingers crossed.

Wish you luck but a 1 hour test is a very short test given all the rubber hoses in the system that expand and then contract possibly compensating for the small leak that you are looking for.
12 hours might be be a more realistic duration for a small leak.

 

[RobertO2023]

So I've got the van back now to monitor coolant and oil levels for a few weeks. No pressure loss after 15psi pressure test (after 1hr). Cap on the expansion tank replaced. I'd seen coolant leaking down the pipe at the bottom of the tank. And the mechanic noticed it was always wet in the area under the cap where the weep hole is. Fingers crossed.

I am pleased for you that is was only the coolant pressure cap - the least cost repair !
As an aside I remember a few years ago there was an issue with VW expansion tanks splitting both OEM and non genuine parts - they were all made by the same manufacturer.

 

[Crippso]

Thanks, yes the tank itself is possibly the next thing to check if the new cap doesn't resolve it.

 

[Fasty-123]

Hi everyone, just thought i would add my story to the thread as it may help some. Also looking for advice on what to do next with it.

I bought a 69 plate 2.0 tdi (102 bhp) with 100k on full vw service history. After about a month I noticed it didn’t require any Ad blue. Then after a bit of investigation I discovered the guy I bought it from has deleted it. Try to contact him, but has disappeared off the face of the earth.

Then the problems started… it started running rough for about 5 mins in the morning on a cold start. If you hold the revs above 1500rpm it smooths out. But it’s like it’s running on three cylinders with an occasional metallic knock. Then for the rest of the day it will run fine, no matter how many times you start it. I then noticed the coolant was dropping on a regular basis.

First local garage diagnosed coolant loss as the Egr cooler, this was replaced but no change.

Then I did a combustion test on the coolant which failed. Took it to a VW specialist who confirmed the head gasket had gone between cylinder three and the coolant. Head was pressure tested and Head gasket replaced. It’s now passing combustion test. However still running rough on cold start on first start of the day.

Specialist now suspects injectors and wants to put a new set in. I’m reluctant due to the cost and them not being a 100% confident it’s that. Given that it runs perfect after it’s warm.

So far about £3500 down and still no fix. T6 ownership is turning into a nightmare.

I have scanned for codes with Carista. The faults that come up related to the charge cooler temperature sensor which I have replaced…still no difference. And the other fault being to a parasitic draw on the battery.

I’ve tried vw injector cleaner and new filters…still no difference.

Other things I’m thinking it could be are; Glow plugs

Dual mass flywheel

Fuel rail sensor

Blocked DPF

Or perhaps the battery needs replacing.


Anyone suggestions on where to go next with it would be appreciated.

 

[DXX]

Sounds like you having a bad time.
Adblue removal has nothing to do with the other issues.
Running an engine with a known or suspected coolant leak is going to wreck it beyond economical repair. If it’s your only means of transport it would still be cheaper to buy a runabout while you get it repaired.
Given the symptoms you have mentioned I’d get an oil analysis done before you spend anymore money.