Coolant Loss

[Wheelyscott]

Hello everyone. Desperate for some help here. Leon FR 64 Reg 184. Coolant Loss last 8 months. Changed header tank and cap, no difference. System pressure checked by local SEAT Dealer both running and non running engine, all ok. Initially, coolant liquid seemed to be blowing out of header tank ( via lid) but since keep level at minimum and that does not happen. Heater system flushed out and heating working fine, hot and cold, so seemingly not a matrix problem.

Son recently started driving lessons in vehicle and with engine getting hotter and under more pressure, coolant level reduces by time of next use, next day. Timing belt and pump replaced by SEAT dealer 6 months ago but problem existed prior to that. Could be leak or problem around EGR or Head Gasket but both expensive jobs.

Any help and guidance greatly appreciated, thanks.

 

[300bhpdaily]

Hi I’d recommend getting a garage to do a leak down test on it to diagnose the problem regarding the excess pressure in the header tank. The coolant maybe be leaking into the combustion chamber while the car is shut off. Does it ever smoke on start up first thing?

 

[Wheelyscott]

Thanks for that. it doesn't smoke on starting. I did have that problem on a previous Toledo and that was a coolant temp sensor issue.

 

[300bhpdaily]

Strange. Out of interest the new header cap you fitted was it a genuine VW item?

 

[Wheelyscott]

Thanks, here goes. All of this done by the local SEAT dealer, referred to as garage.

They changed the header tank initially as they said the silicone bag was damaged and felt this would deal with the issue. I noticed that the existing, pale blue cap then did not appear to lock shut properly, with a click so it went back into the garage. This time they ran pressure tests, did a visual check for leaks and said they only thing they could try was to renew the cap. This time they used a black coloured, original part but a slightly different and newer design ( we also have a Tarraco and its the same cap on that coolant bottle).

This newer cap is a really tight fit and very difficult to get on and off, almost impossible. The coolant level still drops but not perhaps as quick. This week i ordered a febi bilstein part ref Seat 3B0 121 321 which is pale blue with double grooves in the middle and this is much easier to get on and off, it looks like the original cap that came with the vehicle. I put this on two days ago and the coolant level was on the minimum but today its dropped again, even with just 2 x 30 mile trips. If anything, this cap appears as though it might not hold the pressure quite as well. Hope this helps, a huge pain in the backside. I don't mind having to top it up every week or two but any more than that and its a pain.

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[kimimaru]

its the Matrix heater, its blocked, when car gets hot, coolant doesn't flow on the circuit because its blocked so the heat creates pressure and forces it out.
inside the expansion tank there is salt in small bag, when it blows these salts flow to the matrix and blcok it.
its a common fault in vw range car.
Matrix heater is a small radiator inside the car, under the Centre console front of the gear stick down,
Replace the Matrix heater. DIY job 3.5 hours / Garage £300/£500
our FR 184 had same issue.

Empty the Coolant of car
unscrew matrix coolant flow from outside
Remove the centre console side cover both sides, remove bracket and you can see it, then just remove everything until you can slide it out.

 

[Wheelyscott]

Thanks very much for this, you are absolutely correct and this is one that SEAT locally told me about. That said, I believe that this is only the issue if your internal cab heating doesn't work properly. My small local garage cleaned out the system for me to ensure that the internal heating worked well across the full range of temperatures and it does so they ruled it out as the matrix heater. The car is going back in this week though so could mention it again.

Obviously the cost builds up in getting garages to check!

 

[kimimaru]

Matrix heater cannot be cleaned without removing it, the salt stays on entrance, and the system only flows in one direction, and its impossible to flush it in opposite direction due to thermostat closed.
to flush the matrix you'd have to disconnect its aluminum pipe and pressurize it from the out to in, this salt don't dissolve, and that's where they stay, coolant still flow but like 10% only due to blockage it can worn the interior heating but not enough flow to the system so its boiling somewhere and creating pressure so it expand and go out to the expansion tank.
saving money on cleaning is not solution here .
The heater matrix needs new one, or pressurized opposite in opposite direction and pray so it does not get damaged in the process and pray that all salt get out so you can carry on using same old one, or just replace with new one

 

[Wheelyscott]

Thanks again, have printed off your comments so will share with the garage this week.

 

[SuperV8]

My bet would be on heater matrix, I flushed mine several times, would work ok (with heat in the cabin) for some weeks/months but then it would expel coolant out the header tank overflow.

Since fitting a new heater matrix mine been great.

Loads of threads on heater matrix & blocking:

2.0 TDI EA288 184 Timing Belt, Coolant flush & new Thermostat

Did my timing belt, coolant flush/change & thermostat before Christmas and though i'd share a couple pics a comments. Not meant to be a how-to as you can see that in the official maintenance manuals shared elsewhere. I spent the whole morning trying to work out how to undo the exhaust temp...

www.seatcupra.net

 

[SuperV8]

its the Matrix heater, its blocked, when car gets hot, coolant doesn't flow on the circuit because its blocked so the heat creates pressure and forces it out.
inside the expansion tank there is salt in small bag, when it blows these salts flow to the matrix and blcok it.
its a common fault in vw range car.
Matrix heater is a small radiator inside the car, under the Centre console front of the gear stick down,
Replace the Matrix heater. DIY job 3.5 hours / Garage £300/£500
our FR 184 had same issue.

Empty the Coolant of car
unscrew matrix coolant flow from outside
Remove the centre console side cover both sides, remove bracket and you can see it, then just remove everything until you can slide it out.

You don't need to empty coolant system to remove heater matrix. Though you should probably have a full coolant flush/replace/bleed if you have heater matrix blocking issue.
When you pull out the matrix only a small qty of coolant needs to be caught in a small container. Also you don't need to remove any drivers side (RHD UK vehicle) panels. Just remove; glove box, foot well upper panel (panel below blower motor), passenger side panel & blower motor. (if you unplug the glove box connectors you'll need to reset the airbag warning light with a diagnostic interface - so best to disconnect the battery negative terminal before)
Heater matrix slides out toward passenger footwell.

Mine didn't have the separate 'tea bag' type silicate bag in the header tank like you see in the you tube vid's about removing the silicate bag - they (VAG) revised the tank design several times and mine (2015) had a self contained 'receptacle' deep inside the tank - you couldn't see it from the inlet and couldn't remove it. I'm not sure this is the cause for my blockage. I think just general junk/detritus/corrosion in the cooling system blocked mine. Either way I changed my header tank to one without silicate.

 

[Tonythepony]

I'm not a mechanic but I have done a number of jobs on my Seat leon 2013 - I had this problem. I have a 2013 1.6 tdi. It so happened that one day I had the EML come on with a code showing a glow plus was out. I changed the glow plug on cylinder 1 and found that after a dpf regen the loss was less than it was previously . I then replaced the other 3 plugs and now I do not lose any coolant after a DPF. I dont know whether this is a coincidence but i do know that a faulty glow plug will not allow that cylinder to heat up to the required temp to aid a dpf regen so it may be worth a go - My Leon was over 100,00 miles so glow plugs needed changing anyway !!