20th June 2016 - Heater matrix leak

On our return from the Bullet Run I noticed a few drips of something on the passenger side rubber mat and a finger /sniff test proved it to be coolant. So it could only come from the heater which meant the whole dash would have to come out. Bugger!

Water on the carpet means a heater leak!

Removing the dash assembly and heater from a TR7 is not too difficult but it is just fiddly. There are lots of fixings in places you might not expect but the factory workshop manual took me through it step by step with numbered pictures of where all those hidden screws are located. It also gives you the confidence you haven't forgotten something and without it the job would certainly have taken much longer.  I also took lots of pictures along the way to help me remember where all the wires etc were positioned.

Dash and heater unit removed.

With the heater unit out it was clear to see that it had been leaking from the matrix seals.   These are well known to cause trouble in TR7's, they were fine when it was new but after 40 years its not surprising that they can fail. The problem is that they are one of the few TR7 parts that are no longer available. New old stock ones do appear for sale occasionally at inflated prices but they are also 30/40 years old so I would not trust them anyway. The other issue is the metal pipes that go from the matrix to the engine compartment also go rusty and cause problems. There is an expensive modern stainless steel option to fix this as well and luckily my car already had the stainless pipes so a previous owner had obviously been there before me.

The infamous heater matrix seals.

 I ordered a replacement modified heater matrix from Steve Wilcox at S&S Preparations which has normal outlets and does away with the seals and comes complete with hoses, jubilee clips and even the self adhesive foam to go round the outside.

S&S Preparations heater matrix kit.

The only problem was that I had to shorten my nice shiny stainless pipes to go with the new matrix and hoses which felt a bit like sacrilege. They are also expensive so I didn't want to get it wrong and have to buy some more.

Stainless heater pipes had to be shortened.

 The heater unit itself is mostly held together with lots of pop rivets which have to be drilled out. Again the workshop manual was very helpful with step-by-step instructions to follow because its quite a complicated item with lots of levers and flaps to disconnect. Once it was all apart I also took the chance to renew all of the rubber foam seals on the various flaps, most of which had long since disintegrated.

Old foam rubber debris inside the heater.

 Re-assembly was another case of following the steps in the manual and lots of pop rivets to do.  I had plenty of rivets in stock but they turned out to be mostly too long so I had to buy some more short ones, 3.2mm by 6mm long.   Best deal I could find at short notice was a box for £4.99 - but it had 1000 rivets!  I must have enough left over to fix all the TR7 heaters in the UK.

Before and after matrix replacement

These pictures show the stages in replacing the matrix, 1 original, 2 those troublesome seals, 3 new matrix fitted, 4 completed job.

Following advice from Steve Wilcox I connected up the heater pipes before fitting the dash and ran the engine up to temperature so I could check for leaks. Fingers crossed and it was all good to go. 

Putting it all back was just a reversal of taking it all apart, but I also took the opportunity to fit some wire mesh over the main air intake to prevent that experience of dead leaves etc being drawn into the heater and shot out of the air vents into your face.  I also tidied up some of the wiring harness which appeared to have been left to just float about.

Wire mesh on main air intake.

So after all that work it looked like it did before, but without the wet spots on the mat. I also had a heater that all the flaps worked properly and sent hot or cold air where you asked it to.

Job finished.