Heater matrix replacement

[stig414]

Over the Christmas period I will be replacing the heater core (denso) on the wife's Golf.
If I flush the system before replacing the core, am I not moving the issue somewhere else? I will totally drain the coolant and replace with G12 evo but I'm sceptical about causing issues to thermostats and egr coolers by using acid to clean it. There is no sign of oil in the coolant, just the faulty heater core.
If I don't use the flush kit and just replace the core, how long before I'd see any problems further down the line do you think?
The had a new reservoir and lid in the summer btw.

Darren

[Crasher]

We reverse blast the system trough with a pressure wash and then compressed air to get the tap water out, we do this with the heater feed pipes disconnected and bridged. In the absence of compressed air I would fill and run with distilled water for an hour or so. Then change the matrix. Make sure you have the fitting kit 5Q0 898 500 and take great care with the awkward ******* little clamps, they are a PITA and the feed pipe alloy is very soft and easy to damage.

[stig414]

I will run the flush as you describe, but how will that work with the thermostats, as I only have cold water pressure washer? I have a compressor, how much psi do you put through ?
I have the coolant on its way tomorrow, so hopefully, I will get it done before Christmas

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[Crasher]

We disconnect the top hose and take the cap off, then pump water through and this does the none radiator side which we do separately. I carefully blow the system out with water and then let full rip to finish it off, you can't develop enough back pressure to cause any damage.

[stig414]

Well I've swapped out the old for new and noticed a massive difference to the heat output. Although I have a lack of blower from the driver's side. I've checked with VCDS, and you can also hear the flaps move but I'm guessing now the ducting is dislocated from the heater box. At least it's not freezing....... oh wait

In other news, the earth pin has burnt on the inner n/s tail lamp. The joys of vw ownership 🫣

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[Crasher]

The earth pin burning out on the left rear is a problem right across the VAG range, especially Mk2 TT, why the left only I have no idea. The poor flow from the drivers vent is due to the **** design of the Golf 7 upper side vent ducting. It is moulded to the back of the dash as just a U section and it leaks like a sieve and looses all its heat into the dash. The only cure we have found is to remove the entire dash and use rubber/tar/aluminium sound deadening to lag and seal the duct. We tend to use Dyna Matt as we use a lot of it on custom jobs.

[stig414]

Parts ordered for the tail light. At least it won't be a long job. Ordered a new plug, too, as the earth pin is melted inside it and it couldn't release it.

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