Coolant leak - HG replacement?

[wishful-fish519]

Hi guys,

Please excuse me, I know this is a commonly discussed topic but I'm struggling to find a plausible answer that doesn't lead to more questions.

My Seat Leon 2014 1.6 TDI is leaking coolant. Here are the facts:

1. Coolant leaked periodically and had to be topped up monthly.
2. Expansion tank cap flew off while driving ~90km/h and was replaced for a new cap - issue persists however the coolant doesn't leak periodically now but upon checking the reservoir prior to driving once; the entire coolant tank dropped all it's fluid and there was ~2cm of coolant left, way below minimum.
3. 184k km on the odometer.
4. Timing belt & pump changed at 173k km (-13k km).
5. EGR checked by mechanic, dry.
6. Intercooler checked by mechanic, dry.
7. Vehicle checked by mechanic for external leaks, dry.
8. Coolant system pressure-checked by mechanic and no pressure drop.
9. Driver vent doesn't blow hot for the 1st ~15min, proceeds to blow hot for 30min, then goes back to cold for the rest of the journey. Passenger and rear vents blow hot (after the coolant/temp gauge reaches 90 celsius.
   However...
   1. No sod on the windshield.
   2. Car doesn't fog up by itself mid-journey.
   3. No smell of coolant in the vehicle.
   4. No wet carpets.
10. No white fumes from the exhaust after running.
11. Car does not overheat, coolant maintains a stable 90 celsius and engine oil 90-108 celsius.
12. Engine oil checked ten-fold and revealed no signs of coolant leaking in.

Sum-sum my mechanic declared that based on the above; it is not the EGR, intercooler, thermostat, coolant reservoir, coolant hoses, or heater matrix.

I seen @SuperV8 post here that a DPF regen with a blocked heater matrix could cause coolant loss. I do recall driving 800-1000 km on a motorway with no leakage, followed by 2 days of city driving - which resulted in the 2nd time the entire coolant tank dropped all it's fluid in point 2 above. However, my mechanic stated it is not a heater matrix issue due to point 9 above.

I am out of ideas and my mechanic declared this an internal leak and therefore recommended we replace the head gasket. I spoke to multiple people that have mentioned this might be unlikely due to points 10 through 12 above.

Is there any alternatives anyone can recommend? Should I consult w/ a 2nd mechanic? Is it safe to drive on for the time being (I believe this issue has persisted since I purchased the car ~8k km ago)?

 

[wishful-fish519]

still no luck

 

[SuperV8]

Thought you we're AI or a BOT

Do you have coolant residue around the coolant tank? If yes this would be evidence that the cap over pressurised and dumped the excess coolant.

Heater matrix is very common to block up/restrict - which causes local over pressurisation of coolant which escapes out the coolant pressure relief cap, as the matrix is on the micro cooling circuit shared by the EGR cooler. After a DPF regen there is a load of heat the cooling system which needs to be pumped round to get rid of - which is can't due to the restriction. Blocked aux pump could also cause this.

I would get a head gasket test kit - to check for exhaust gasses in your coolant - to help rule out head gasket failure.

example:

Did if overheat when the 'coolant cap fell off'?

 

[wishful-fish519]

Thought you we're AI or a BOT

Do you have coolant residue around the coolant tank? If yes this would be evidence that the cap over pressurised and dumped the excess coolant.

Heater matrix is very common to block up/restrict - which causes local over pressurisation of coolant which escapes out the coolant pressure relief cap, as the matrix is on the micro cooling circuit shared by the EGR cooler. After a DPF regen there is a load of heat the cooling system which needs to be pumped round to get rid of - which is can't due to the restriction. Blocked aux pump could also cause this.

I would get a head gasket test kit - to check for exhaust gasses in your coolant - to help rule out head gasket failure.

example:
View attachment 52571

Did if overheat when the 'coolant cap fell off'?

Hi SuperV8, thanks for the reply & no worries

New driver so was not watching the temps when it fell off. All the information above is something I learned from my mechanic/others after this started happening. I assume there is warning on the car system if the car reaches a certain temperature - which did not go off. Just a low coolant fluid level warning.

I am trying to sort a head gasket test kit for tomorrow so I will report back when I'm able to get my hands on and do it on the car.

In terms of heater matrix/aux pump; where would the coolant go? The general, personal & uneducated hypothesis I have gotten from your comments on this forum, now, and from my mechanic is that it would be unlikely to completely boil out and even if it did, or remained inside the heater matrix - there would be sod from it on the inner side of the windshield, a sweet smell of coolant in the cabin, wet carpets, windows would fog up mid drive etc.

 

[nd-photo.nl]

It is a bit hard to spot at first, but the reservoir has a builtin "channel" for overspilling coolant. On the picture below, its the protruding part of the reservoir on the left.

In other words, it dumps the coolant in the engine bay

 

[wishful-fish519]

It is a bit hard to spot at first, but the reservoir has a builtin "channel" for overspilling coolant. On the picture below, its the protruding part of the reservoir on the left.

In other words, it dumps the coolant in the engine bay

I'm attaching photos of my coolant reservoir (apologies about the lighting). Since it does not look the same; possibly the reservoir has been replaced?

 

[SuperV8]

I'm attaching photos of my coolant reservoir (apologies about the lighting). Since it does not look the same; possibly the reservoir has been replaced?






View attachment 52581View attachment 52583View attachment 52584

On your version of coolant tank, the overflow is in the centre underneath, so if your coolant goes above the max pressure of your cap - coolant with be expelled through this hole, so you may see coolant under and around your tank.

Your engine mount bolt is looking very rusty - maybe your coolant has been pooling here.

 

[SuperV8]

Hi SuperV8, thanks for the reply & no worries

New driver so was not watching the temps when it fell off. All the information above is something I learned from my mechanic/others after this started happening. I assume there is warning on the car system if the car reaches a certain temperature - which did not go off. Just a low coolant fluid level warning.

I am trying to sort a head gasket test kit for tomorrow so I will report back when I'm able to get my hands on and do it on the car.

In terms of heater matrix/aux pump; where would the coolant go? The general, personal & uneducated hypothesis I have gotten from your comments on this forum, now, and from my mechanic is that it would be unlikely to completely boil out and even if it did, or remained inside the heater matrix - there would be sod from it on the inner side of the windshield, a sweet smell of coolant in the cabin, wet carpets, windows would fog up mid drive etc.

To clarify on how the heater matrix can cause external coolant loss.
Our cooling systems are quite complex and have three district circuits.
The heater matrix is in the mirco-circuit and is in series with the EGR cooler. When the engine is cold - or just switched off there is a small electric support pump to circulate coolant around this mirco-circuit. When the engine is upto temp - the main switchable coolant pump takes over and this small pump switches off.
During a DPF regen - the exhaust gasses get really hot, above 500+ deg C - and a lot of that heat gets dumped into the coolant via the EGR cooler. If the heater matrix or the support pump has a restriction, then that also restricts coolant flow through the EGR cooler - meaning the coolant temperature in the egr cooler increases too high - which increases its pressure above the 23psi pressure release rating of your coolant tank cap - which means your coolant gets dumped out your tank overflow into the inner wing in your engine bay.

When this happened to me, it would empty the contents of the tank in one go - so go from full to empty and put on my low coolant warning light.
It was not a slow gradual coolant loss.