shaunje 10 Posted November 5, 2013 Hi all, My Corrado 16V KR is confusing me... The heater is working perfectly fine until after an indicated 90 degrees where it just blows stone cold. I have fitted a new water pump and thermostat today and the issue is still there. I cant work out what is causing this issue. I have noticed there is what looks like a small valve body in the pipes near the bulkhead going to the heater matrix. Is there a chance this component is somehow at fault? Cheers, Shaun Quote Share this post Link to post Share on other sites
davidwort 0 Posted November 5, 2013 Yes, there should be two valves, one in and one out and a small linking hose, this makes up the pressure relief or by-pass valve to prevent a blockage in the matrix causing a build up of pressure and explosion of hot water into the cabin. the valves do stick with age, you could remove them and soak in lemon juice or kettle descaler or just remove them from the system, but to do the latter ideally you want a new matrix as these are stronger than the originals Quote Share this post Link to post Share on other sites
shaunje 10 Posted November 6, 2013 Thank you very much mate! Very helpful. I'll remove said valves later. How do I go about getting a replacement pair of valves? No idea what they're called! Quote Share this post Link to post Share on other sites
davidwort 0 Posted November 6, 2013 they're heater matrix by-pass valves, but I think they're discontinued, if you can't free yours off or find any second hand then ideally you want to fit a new matrix (which is a pain) or risk running it without, the problem with the early matrix seems to be where the matrix itself joins it's in/out pipes it rots there basically, so any blockage forming inside the matrix can cause a pressure build up and water/steam leak into the car in the direction of your feet and steam to the windscreen, so you can see why vw fitted the valves as a recall. The mk3 golf/later part number of (valeo) matrix is stronger AFAIK and later cars didn't need the by-pass. Running without is a gamble, if your cooling system is clean and has had regular coolant additive changes then you could be fine for years, on the other side there's a few people on the forum that have had them pop. Quote Share this post Link to post Share on other sites
shaunje 10 Posted November 7, 2013 I've taken them off and cleaned them out thoroughly as well as a light bit of pillar drill modification which seems to have made a nice difference :) Quote Share this post Link to post Share on other sites
