Heater pipe work issue May 07, 2026, 04:50:58 PM Hello, I am just trying to sort out my 1986 golf gti which I rally on HRCR events. There is a water leak under the bonnet from the heater return pipe. I note there is a second pipe linking the hot water in pipe to the hot water out pipe into the heater matrix ( I renewed this last year) which uses a smaller 6mm diameter hose. Does anyone know what this is for if I eliminate this pipe I get rid of my leak, I may just by pass the heater matrix for the summer. The problem part is a 3 way metal union I can’t see them listed anywhere …. Any suggestions appreciated. David
Re: Heater pipe work issue Reply #1 – May 07, 2026, 08:02:14 PM I think the pipe you are asking about was fitted by vw years ago on a vehicle recall. The reason for it was that the heater matrix was prone to failing and hot water entered the footwell. There is a fix by fitting a mk3 matrix which is a direct replacement. Alternately just remove it and either fill the gap with a piece of pipe or replace the pipes altogether. On rereading it i note you have replaced the matrix so i would just remove the valve and either bodge the joint or replace the heater pipes. Last Edit: May 07, 2026, 08:06:50 PM by scs 1 Likes