MOT prep checks and Heater Matrix problem

adamskibx · Post by **adamskibx** » Thu Mar 30, 2006 1:31 am

I have now got the GT to a stage where it has a good working engine, and it drives around etc. Im going to take it a long way round to the MOT station and give it a good workout first, but first I must replace the damn heater matrix!! Couldnt work out why my carpets were wet as the headlining is dry, then I noticed a trickling water sound when the heater is turned on. So tomorrow I must replace the heater matrix. I only have the Haynes for the Mk1 and it looks like a reasonably quick job: Remove lower facia panel etc, undo tap to matrix pipes and so on. However im told its a sod to do? If I cant get it done in time for the MOT, is it safe to just link up the suply and return hoses to the bulkhead? I have a second fan installed now as im paranoid about overheating, and I can just turn this on or off on the dash with a manual switch, so I dont suppose cooling would be a problem if I did this. Anyway, fingers crossed I can get it swapped over for the other one fairly quickly. Then I plan to spend the rest of the day checking the car over and making sure the rear brakes are not seized (my old 14 did this as it had been sat at the dealer for about 8 months and the pads rusted to the caliper and wouldnt budge). Ideally I would buy new HT leads as they are now as old as the car (20 years!), but it seems imposible to get the right ones. I cant use the TRS ones as the dizzy cap for the GT has female connectors for the HT leads, and not one set of leads in Halfords has male ended leads. I tried finding the lead set for the older BX's, and I could see that the set they refered me too were female connector leads and so wouldnt work.

AlanS · Post by **AlanS** » Thu Mar 30, 2006 1:42 am

Just by-pass it. We have done this on two of our cars with no evil side effects.
A word of warning though; be extremely careful working with the plastic fittings where they come through the firewall as they are unobtainable as a seperate entity and if you ever break one (often caused due to hoses hardening with age) you need to buy an entire matrix to get a set.
If anyone has a set to sell, they usually want an arm and a leg for them too.

Alan S

adamskibx · Post by **adamskibx** » Thu Mar 30, 2006 1:59 am

Cheers Alan. Thinking about it, I did have to be quite agressive with the pipes connecting to that plastic thing, but as the tap is after that point, and the leak is 10 times as bad with the heating on, I suspect it is the matrix itself. Fingers crossed I didnt split that thing anyway! Sounds like a night mare trying to get hold of one, and I cant afford a brand new matrix at the moment. Have to admit, heating is always nice to have over here lol! Ill see how hard it will be to swap them over and if its going to eat into time I could eb spending on other jobs too much, then ill leave it till another day.

AlanS · Post by **AlanS** » Thu Mar 30, 2006 2:17 am

If you've cracked a pipe you won't be the first.
It won't leak until it's switched on as if it's the return line there's little pressure on there until the valve is opened and the coolant starts to circulate. Either way, it's a $#!+ of a job, but if it's the pipe, it may save you the cost of the matrix.

Alan S

DLM · Post by **DLM** » Thu Mar 30, 2006 11:59 am

I've been in a similar situation before now, Adam, and used a "known good" matrix from a spares car to replace the old one. I guess you may have such a thing around, or at least remember what it's like to get the aircon heater assembly out. It gives a good feel for what is and isn't possible. When taking the old one out, I didn't take the dashboard out, and ended up more or less dismantling the whole steering column assembly to make room. When replacing, I went the dashboard-out route for easier access.

I may be in the same situation that Alan alludes to though (cracked plastic tap assembly), as I seem to have a persistent damp stain on the driver's-side carpet. How you work out which it is, is another matter....

Oscar · Post by **Oscar** » Thu Mar 30, 2006 2:44 pm

This is a tricky but not impossible job. It can be done with the steering assembly moved out of the way - you don't need to take the dash out.

When you get the old one out, do a couple of dry runs on re-fitting it and manouevring it back into position before you start with the new one. This will make it a lot easier.

Be aware that the union plates from the matrix and the inlet pipes overlap as you are pushing the matrix in (this will make sense when you are doing it). You can gently use a long slim screwdriver between the two plates to lever the matrix over the inlet pipes and into place.

Time - 3 - 3.5 hours.