Heating ... again!

Discussion in 'Mk2' started by PhilRyder, Jan 8, 2021.

  1. PhilRyder

    PhilRyder Paid Member Paid Member

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    I know, I know, this has been done to death and I have read a great many threads on the subject but I do have a couple of questions.
    Today I set about trying to make the car warm up a little better. The issue is that the car doesn't seem to warm up very quickly with the gauge barely getting out of the first white section unless driving in traffic or stationary. I thought this would be linked to the lack of warm air coming out of the vents.
    I started by taking the matrix bypass valves off and popped them in an ultrasonic cleaner. They were apparently free and I could blow through them easily.
    While all the pipes were off I stuck a hose through the matrix which seemed to be free flowing.
    I was also going to change the thermostat but I ordered the wrong one so stuck the original back in.
    Re-fitted the bypass valves and filled it with water and Wynns. I let the car idle for a good twenty minutes until it seemed the thermostat was open, hot water was running through the lower radiator hose and eventually the fan kicked in. However, there was no hot water getting past the alloy bypass valve and as a result no hot air out the vents.
    So, I took the alloy valve off and replaced with copper pipe as per the conventional wisdom. This time no hot water getting past the plastic valve. Next I replaced that one too with copper pipe.
    Now I have hot water flowing in and out of the matrix. The air coming out of the vents is definitely warmer but certainly not at a level I would expect.
    I have now drained the coolant (it was deffo dirty) and refilled with antifreeze and water.

    So my questions are, can the matrix still not function properly even though water is flowing through it or is my problem the diverter flaps? They have definitely lost their foam as a lot has come out through the vents.

    Also, am I asking for trouble with an unknown age of matrix and the risk of it bursting, having removed the bypass valves?

    Thank you in anticipation.
     
  2. costel1969

    costel1969 Paid Member Paid Member

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    I'm pretty sure you're in "replacing the matrix and foam" territory Phil
     
  3. PhilRyder

    PhilRyder Paid Member Paid Member

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    This is what I feared and trying to avoid :cry:
     
  4. costel1969

    costel1969 Paid Member Paid Member

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    You can do it Phil - I have the utmost faith in you..
     
  5. PhilRyder

    PhilRyder Paid Member Paid Member

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    Thanks Mate. I've just put in an order with Heritage, l'll have to do another now [:[]......
     
  6. costel1969

    costel1969 Paid Member Paid Member

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    Well you have probably read all the threads - 2 factions (Remove the dash completely or keep it in place) I would be in the first camp, gives you a chance to check everything over (inspect wiring, replace dash bulbs etc.)
     
  7. PhilRyder

    PhilRyder Paid Member Paid Member

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    I will need to do the quickest version at the moment as it's a daily driver. I can revisit it in the summer. I'm sure the distribution channels to the windscreen need some attention too. After all what else am I going to do with my annual leave - not likely to be going on hols.
     
  8. costel1969

    costel1969 Paid Member Paid Member

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    Fair point re: holidays in fairness. If you keep the dash in I believe (and may stand corrected on this) things can get a bit fiddly/awkward and what you may gain in not removing the dash may be lost in trying to get in/out/aligned etc. but I will leave it to bigger VW brains to confirm or contradict this
     
  9. Tristan Forum Junkie

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    I've only ever done them with the dash left in, just removed the lower sections. It's not as bad as you'd think tbh. I open the bolts holding the top section so it can move, which help.

    Also, re the matrix bypass valves, you don't need them. Straight in the bin. They were only for older, weaker heater matrixes (matrices?). I have NOS ones you're welcome to if you're looking for the OEM appearance, but I wouldn't bother. The pipes to dump them are available off the shelf, or you can use 16mm OD tubes.

    One tip re the new matrix, lots of them come coated with an oily substance, wash it well before fitting, as it'll stink otherwise and keep fogging the screen.

    And re the stat.. I had a mk2 once that I couldn't get up to temp in cold weather, I tried 3 stats, 2 genuine VW, before I realised the seat where it sat against overhead, in the water pump housing, was corroded, and coolant was bypassing around the stat.


    If you could source spare heater flaps from Brendon Moss or similar, you could have them recovered and ready for the heater box rebuild. So it'd be a one night job. The last few I did I used lightweight carpet, like what you would see on the walls of a camper van or nice crew cab conversion, and glued it to the flaps, each squashed between some planks, overnight.

    A mk2 with a properly working heater is a pleasure on a winter's day.
     
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  10. Simon Peter Dodgson Forum Member

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    Mine worked well until I cracked resoirvoir sensor. Never worked properly afterwards
     
  11. Savagesam

    Savagesam Moderator Staff Member Moderator

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    I never took the dash out either, wasn’t too difficult.
    I also took out those valves in the engine bay.
     
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  12. Tristan Forum Junkie

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    I always knew you were wise beyond your tender years.
     
  13. PhilRyder

    PhilRyder Paid Member Paid Member

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    Thanks All, very helpful. I'll order a new matrix and thermostat today and maybe we can get it done next weekend. I think someone has been in the thermostat before and there are two seals where I think there should only be one which could easily mean the stat is not seated properly. The top hose to the radiator gets hot quickly which I also don't think it's correct and would indicate a faulty or non sealing stat? Thank goodness the parts are cheap :)
     
  14. rubjonny

    rubjonny Administrator Staff Member Admin

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  15. PhilRyder

    PhilRyder Paid Member Paid Member

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    Thank you. I had a read of your guide, very helpful. While warming up the bottom rad hose stayed cold for quite some time. The top one got hot quite quickly though. Does that sound right?
     
  16. rubjonny

    rubjonny Administrator Staff Member Admin

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    it should stay cold till the gauge gets close to or just past 1/2, it may be the dash is under-reading though if the hose does stay stone cold. if its the original heater matrix its going to be well past due for a change though especially if the coolant servicing hasnt been kept up
     
  17. Tristan Forum Junkie

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    Jon, I wouldn't be shocked if VW had a recommendation on a service interval even on them?
    When I was a boy mechanic, the guidebooks back then recommended a full coolant change every 2 years, and a new rad every 10!
     
  18. PhilRyder

    PhilRyder Paid Member Paid Member

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    Quick update. 8 miles to work - next to no warm air :( 10 miles home with a stop on the way and there was warm air for the last 2 miles.
    New thermostat and matrix ordered, as well as the thermostat cover.

    Question - how many seals should be in there? Just one between the stat and the cover or one either side of stat?
     
  19. costel1969

    costel1969 Paid Member Paid Member

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    Just one Phil - never come across a double seal on any vehicle I've owned.
     
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  20. PhilRyder

    PhilRyder Paid Member Paid Member

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    Thank you :thumbup:
     

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