Heater matrix replacement

[Rich K]

Hi,

More work carried out on the 81 drophead, this time dismantling the heater unit and replacing the matrix. It didn’t appear to be leaking but as we had the thing out it made sense to do a complete refurb. After reading the various posts on using an alternative matrix and not wanting to pay the inflated price that the usual suspects are charging for what appears to be an inferior quality unit, I sourced the VW/Audi matrix from an eBay supplier. This is a Nissens 73950 and was fitted to most VW/Audi vehicles through the late 80’s and the 90’s. A nice modern aluminium and plastic unit. Price £21.28 with free delivery! That saved me about £100 plus postage compared to the one offered by the usual suspects. As you can see from the pictures this unit is virtually identical in size to the original and will connect via 16mm id coolant hose onto existing pipework. It looks like I will need to relieve the plastic heater casing slightly where the pipes exit but apart from that it will drop straight in.

[Howard722]

That looks a great solution. Are the pipes coming out straight/vertical or is there a slight angle/tilt to them?
H x W x D would also be good?

[Rich K]

Hi Howard,

The dimensions of the matrix as per the attached picture. The pipes are very slightly angled and as such it may be necessary to lightly remove a little material from the plastic heater casing in order to allow the matrix to seat into the housing. Also if you are reusing the original steel coolant flow and return pipes you will need to shorten them and use some 16mm id coolant hose to make the connection between the those pipes and the inlet/outlet pipes on the matrix. Hope that helps.

Cheers, Rich.

[busheytrader]

Hi Rich, some years back there were posts about fitting a VW matrix. I’d fitted stainless steel pipes heater pipes and probably the last normal priced rubber seals a year or two earlier.

I had to bypass the heater matrix again last summer as coolant appeared to be weeping from the seals. ( I think a pair sold for £50 on eBay a while back)

How easy have you found splitting apart and reassembling the heater box? I had trouble last time with the plastic melting when drilling out the rivets and used the best parts from 3 heater boxes .

[Rich K]

Hi Bushytrader,

This is actually the second time that I have taken apart a heater box, albeit the first time was probably 10 years ago. I didn’t have much trouble drilling out the rivets as long as long as the drill bit was nice and sharp. In my experience a worn bit tends to take longer to penetrate the rivets and hence more heat is generated leading to melting of the plastic. I took plenty of pictures so that I had a decent record of what goes where for the reassembly. This particularly helps with correctly positioning the various control levers and linkages. I also replaced all the foam with neoprene of an appropriate thickness after de-rusting and painting all the component metal parts. In my opinion It’s a time consuming job but not prohibitively difficult if you work methodically and follow the workshop manual procedure if you get stuck.

Cheers, Rich.

[tr7dan]

Did my heater a while back but repaired the original instead of replacing. I cleaned it out first with descaler (I might have filled it with vinegar - can't remember) then made up some copper connectors, which I soldered in place, using plumbing tube and a couple of brass fittings which I filed and ground to fit. I flushed it out with boiling water and then pressure tested it @ 2 bar for 24hrs - fortunately no drop . Lick of black paint and it looked fine.

I made up my own pipes, again in copper and pressure tested the whole thing again once it was assembled. Regarding the rivets - I re-assembled mine using small M3 or M4 (can't remember) button head socket screws and nylock nuts so it can all be taken to pieces again without drilling rivets.

Probably a bit easier for me to do it this way being in the plumbing trade and didn't cost anything as I already had all the stuff in my van / workshop.....

[Howard722]

Thanks for the details Rich.
I`d always fancied having a spare rebuilt `good to go` heater unit in my spares stash, so a project to work at now.
BTW, info picked up somewhere seemed to suggest that `shorting out`(by-passing) the heater matrix to combat leakages was not a good idea as this can cause overheating maladies-and its noteworthy that despite what seems all to `normal`- there is no hot water valve in the system so the matrix is always in circuit.-any thoughts peeps?

And TR7Dan,-yep good work there and I also felt this could be doable etc. but my concern was can soldered joints cope under presuure (15psi) at much higher temperatures than domestic hot water?

[FI Spyder]

The VW heater core is definitely the way to go, I haven't had to do that yet as the original A/C heater core doesn't use the seals so no leaks so far. I attribute the change to using a 1996 Saturn alternator when the original goes as a low cost alternative for a high power unit. An alternator is an alternator and they mostly look the same.

[Hasbeen]

Really nice work, BUT,

Have you ever thought of migrating to Queensland? I disconnected the water from the heater of my first 7, in 2000, & have not had water piped into the cabin of a Triumph since.

Hasbeen

[busheytrader]

Rich - At under £22 for a new item it’s worth a punt, so I’ve ordered one. Yes a super sharp drill bit before I start.

Dan - Kudos to you for a neat solution and using button head bolts and nylocs to reassemble. I’d probably go through 2M of pipe before I got the contours right. I’ve yet to meet someone who’s had the original matrix fail, it’s always been the seals. I’ve seen the effects of rad seal on the matrix in our group, instant clogging and no flow.

Howard - I’ve driven for extended periods on hot days with the heater bypassed in my V8 engine bay. It’s never been a problem. As you say the heater matrix is in 100% full flow the whole time. I can only guess that if the radiator has silted up and it’s cooling is marginal, there are underlying problems causing this.

[Howard722]

Howard - I’ve driven for extended periods on hot days with the heater bypassed in my V8 engine bay. It’s never been a problem. As you say the heater matrix is in 100% full flow the whole time. I can only guess that if the radiator has silted up and it’s cooling is marginal, there are underlying problems causing this.

The `non-bypassing` question relates to the standard 2L engine. Hasbeen says he`s not a problem in Queensland though, so ??-jury is out I guess.

[Rich K]

Hi Bushytrader,

If you still get problems with melting plastic and hence oversize holes, you could use small washers at the rear when you compress the rivets. When I was taking the latest heater unit apart, it was clear that the guy who had originally assembled it had made a mistake in a couple of places and had used washers to correct his riveting errors.

Great to see that there is still a group of people out there reading and using the forum. I had recently started to think that the lack of activity meant that most had now moved over like sheep to the FB dark side.

Cheers,
Rich.

[Hasbeen]

In both the 7 & 8 I bypassed the heater, not shut down the flow.

The 8 originally has a shut off system when I bought it, which I changed to a bypass, chasing overheating, which ultimately proved to be caused by lean mixture at small throttle openings at lo revs.

[seven]

I'm still here, not contributed much though now that Ruby is on the back burner once again
I fitted a VW Jetta heater matrix to Ruby some years ago, I believe they are pretty much the same as you have or fitting I am hoping to get back on the my TR7 soon, wiring needs addressing and the Rover SD1 exhaust mated to the TR8 system. Then she will be fairly close to booking her in for an MoT

[busheytrader]

Great to see that there is still a group of people out there reading and using the forum. I had recently started to think that the lack of activity meant that most had now moved over like sheep to the FB dark side.
Cheers,
Rich.

I totally agree with you Rich. There was and still is a whole breadth of knowledge shared by those who’ve faced and solved the same problems for everyone.

Adam