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Coolant loss from tank on motorway journeys or high speeds

Legojon

I only wanted a remap
Staff member
Moderator
Jul 7, 2015
5,130
2,594
But would you not see traces of that left on the engine or pump.
Yeah... but if it's leaking out the back of the engine, it can be really difficult to spot. Plus... if it's dripping onto something hot, it may leave no trace.
 

Seastormer

Cupra 280/CBF1000
Apr 25, 2014
4,033
279
64
Edinburgh (Scotland)
Yeah... but if it's leaking out the back of the engine, it can be really difficult to spot. Plus... if it's dripping onto something hot, it may leave no trace.
My 280 had the coolant level drop a bit several times when it was new for the first 6 months or so , no leaks could be found and passed the pressure tests also. Now it does not do it at all and it has passed its 5th year with no problems and still on same pump, very strange.
 

black_sheep

Active Member
Mar 10, 2013
496
208
My 280 had the coolant level drop a bit several times when it was new for the first 6 months or so , no leaks could be found and passed the pressure tests also. Now it does not do it at all and it has passed its 5th year with no problems and still on same pump, very strange.
This phenomenon is quite usual on the MQB platforms, and is usually attributable to an airlock in the coolant system that can take a little time to settle, work its way out of the system when the car leaves the factory.

The coolant loss the OP is suffering with is also very normal on the EA288 diesel, especially the 184 ps variant, and is sporadic in nature, and is not easily detectable via a pressure test.
 

Legojon

I only wanted a remap
Staff member
Moderator
Jul 7, 2015
5,130
2,594
My 280 had the coolant level drop a bit several times when it was new for the first 6 months or so , no leaks could be found and passed the pressure tests also. Now it does not do it at all and it has passed its 5th year with no problems and still on same pump, very strange.
Well, I'm really jumpy after having the headgasket done. Since I've had my car (2.5 years) it's never been able to hold coolant. If I fill it past the max, it disappears. If I top it to the max it disappears. I know that might be logical. After all it's an expansion tank. But I know of at least 3 MK2s that can be filled past the max and keep it. Mine's just picked a level it likes and has stayed there since October last year. Weird.
 

YKFR

Active Member
Jul 23, 2019
51
8
If it was the head gasket, would you not get that creamy gunge on the underside of the oil filler cap to confirm this?
All that looks fine. Car drives fine too. No perfomance issues, no smoke coming out, no oil color change etc...

Coolant has not been lost in over 16 days now. I even drove in higher speeds while in low gears to build up tension or pressure.

I really dont know what is going on but I am living with it atm...
 

YKFR

Active Member
Jul 23, 2019
51
8
This phenomenon is quite usual on the MQB platforms, and is usually attributable to an airlock in the coolant system that can take a little time to settle, work its way out of the system when the car leaves the factory.

The coolant loss the OP is suffering with is also very normal on the EA288 diesel, especially the 184 ps variant, and is sporadic in nature, and is not easily detectable via a pressure test.

By OP I assumed you meant myself? I had to look that up gosh... My friend told me to look up the engine of the car I was interested in buying and what issues that model might be giving others. I didn't not really listen much to that advice. Which I now know that I should have followed and done more research... Like on this forum.

About my 184 model. SEAT have already tested the car and they marked it down as no fault (because they couldn't find one from the amount of tests they did).
 

YKFR

Active Member
Jul 23, 2019
51
8
Why did they not test for combustion gases in the coolant? What kind of primates are working as Techs there?
The initial check was for £80 and that involved a pressure test and some of their checking. However once they could not find any leaks they called me up and said that they had to stop checking cause they couldn't find the issue.

However... They also said that If I want to take the car it was free of cost cause they couldn't not provide me with a solution or reason. But the two things they suspect are either the Head gasket or EGR (Cooler I'm assuming)... But to go that far they would need the car for 2 hours more and charge me £200 + £80.

So I just took the car back. I don't have so much to pay atm for just a check. I assume they would have carried out a combustion test or head gasket compression test at that stage.
 

phate101101

Active Member
Oct 6, 2015
33
18
i understand it may be too late now but an important point to highlight again - when buying anything, not just a car, you should always bring it straight back to the place you bought it from right away. I get the impression you felt you didn't have any recourse with the trader because it wasn't a banded garage etc, but you did.

I know this doesn't help you now, and I hope you get to the bottom of the issue before you get to the bottom of your wallet, but just keep it in mind for the future.
 

LouG

Active Member
Dec 1, 2017
1,328
477
Nelson, New Zealand
I am really surprised at the attitude of your dealers. All that I've dealt with here consider diagnosis as part of the warranty cost on them. They treat it as good customer relations. My Toyota dealer spend around three hours trying to resolve a problem with the head unit and didn't charge.
Even when I was in the trade, we did initial diagnosis free. But charged when we actually had to start removing parts. Even then we cut back the cost if nothing was found.
 

YKFR

Active Member
Jul 23, 2019
51
8
Update:

After 19 days of no coolant drop I finally got the coolant to drop...

I thought to my self lets try taking the car to high speed and checking for leaks right away. So I did exactly that, drove the car to 90+ mph and parked it up right away... And not really to my surprise the coolant bottle/tank was more than half empty.

Water/coolant was all around the bottle and under it. It was fresh and it was from the bottle...

Anyone can give me a better guess as to what this is caused by? There was no leak under the car I checked that too.

20190821_233801.jpg


The metal part circled was really wet with coolant...
 
Last edited:

bgb

Active Member
Jan 22, 2019
576
293
Update:

After 19 days of no coolant drop I finally got the coolant to drop...

I thought to my self lets try taking the car to high speed and checking for leaks right away. So I did exactly that, drove the car to 90+ mph and parked it up right away... And not really to my surprise the coolant bottle/tank was more than half empty.

Water/coolant was all around the bottle and under it. It was fresh and it was from the bottle...

Anyone can give me a better guess as to what this is caused by? There was no leak under the car I checked that too.

View attachment 9465

The metal part circled was really wet with coolant...
I’m more than certain to have a block somewhere. And I’m still hedging my bets on heater matrix! You’re 100% sure your heaters get up to roasting heat and are unified across all vents?
 

KoNG

Active Member
Jul 27, 2016
234
13
Kent / Barking
ykfr i had similar issue replaced heater matrix and done complete coolant flush and problem is gone

The coolant is leaking from bottle there is pressure valve
 

YKFR

Active Member
Jul 23, 2019
51
8
I’m more than certain to have a block somewhere. And I’m still hedging my bets on heater matrix! You’re 100% sure your heaters get up to roasting heat and are unified across all vents?
Ill have to take it back to SEAT? And tell them about this issue? Maybe now they will have a better idea of what's going on now...

And yeah the pipes are hot but I am not an expert so I can't guarantee that it isn't the heating matrix
 

YKFR

Active Member
Jul 23, 2019
51
8
ykfr i had similar issue replaced heater matrix and done complete coolant flush and problem is gone

The coolant is leaking from bottle there is pressure valve
How did you end up making that deduction about the heating matrix, did your garage check it and tell you? And how much did it all cost to fix the issue?

Yes if the coolant is leaking from the bottle then its pressure building up somewhere
 

bgb

Active Member
Jan 22, 2019
576
293
Ill have to take it back to SEAT? And tell them about this issue? Maybe now they will have a better idea of what's going on now...

And yeah the pipes are hot but I am not an expert so I can't guarantee that it isn't the heating matrix

does the air come into the cabin at full heat hot? From passenger and drivers side? As if not uniformed this points at un-even coolant flow in matrix fins, ie blocked capillaries :)
 

YKFR

Active Member
Jul 23, 2019
51
8
I had a car like this once

changed everything and spent a fortune trying to get it right.
My advice to you, sell it to someone else, I don't think you'll find a real solution.
I have been told to do that but I don't want to lie to someone and say that it's perfect when its not. I know how much trouble I'm having so I don't want to put someone in same bother... And if I tell them the truth no one will buy at good pice
 

YKFR

Active Member
Jul 23, 2019
51
8
does the air come into the cabin at full heat hot? From passenger and drivers side? As if not uniformed this points at un-even coolant flow in matrix fins, ie blocked capillaries :)
It is same level of heat when the air is coming to your faces (both dials have to be on high temp) however when the setting is on air going to windshield drive side half of windshield take a little longer to clear up but passenger side clears up almost immediately... I checked the air coming under drive side windshield and it wasn't anywhere hot as the left side. But after switching the settings from face back to windshield the air takes a little while but also gets hotter on driver side windshield...

Hope that made sense to you
 

bgb

Active Member
Jan 22, 2019
576
293
It does and was the same as my Golf GTD, (same engine and problems).

Have you gone to a reputable independent VAG group specialist? As much as dealers like you to think it, the tech guys are reading problems and possible solutions from a tick sheet. Sometimes a good independent will be more in depth.

It took me a few months and back and forth with VW UK to strip and find the issue, which eventually was casting sand as I've said before. Even after they 'fixed' it, it reappeared and the car was sold to a franchise shortly after...

Luckily, mine was under warranty so didn't pay out.
 
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