Heater Core Matrix - a baptism of fire!

[TheBadger]

Hi,
I'm new to the forum and have recently acquired a 1998 940 Celebration auto estate after 25 years since my last Volvo. The crunch is on close inspection it appears to have the archetypal heater matrix issue - the drivers side footwell is soaked in coolant... Having stripped out the carpet and pulled up the felt underlay the leak seems to have been a long standing problem and having seen the work involved in stripping out the matrix I can understand why the previous owner didn't get it fixed.
I have a number of questions, the first is, is there a way of diagnosing whether the the matrix has failed or is there a more simple series of possible issues to look at in the first instance that may save a strip out.
Secondly, if I have to strip it out, which is the best quality matrix and where do I find one - I hope to keep the car for some time and have some fun with it so its a job I only want to do once!
The felt underlay is ruined, as is the vinyl/foam firewall covering - is an OEM replacement available?
Not directly related, but as I have the centre console in bits and the auto selector back light is not working I thought I'd replace the bulb - how the heck do you get to it? I've got the shroud unclipped but I can't seem to manoeuvre it so I can get to the bulb.
And lastly - I've disconnected the heated seat switches which are colour coded so easily recognised, but there is a connector that is not attached with blue and grey wires - what should this be connected to?
Thanks in advance.

[loki_the_glt]

Welcome to the Forum.

There's a thread detailing heater matrix replacement in the 7/900-series articles section and, yes, it is a PITN that will take at least a full day once you've sourced a replacement.

The first thing to do before ordering a replacement is to measure the distance between the two connectors where they go through the bulkhead: there are several different matrixes(matrices?) for A/C and non-A/C cars. A temporary fix is to by-pass the matrix by joining the two hoses together which will at least stop any more coolant dumping into the passenger compartment.

The fault may lie with the heater control valve rather than the matrix itself but you're still going to have to pull apart the interior.

Clive Brook Volvo in Huddersfield (I'm not an employee, just a visitor to their premises) have a "Heritage Club" that meets on the second Saturday morning of every month; they might be able to help with the underlay and firewall covering, as might Rybrook in Warrington or Chester.

[Rversteeg]

Don't be tempted to buy a Nissens aftermarket matrix, but go for OEM. Almost triple the price, but you will not get nearly as much heat out of the Nissens one. If it weren't that time consuming, I would redo the work with an OEM one. Another option is refurbishing the original matrix, but that is only feasible if you can afford not using your car some several days.
A 1998 940 will probably have a vacuum operated heater control valve located in the engine bay, in that case coolant in the interior is certainly a defective matrix. To postpone the operation it is quite easy to bypass the matrix with a piece of 12 mm (?) copper pipe, bent in a U shape.

[lnparry]

Hi Badger and welcome to the forum.

I have the same problem with my matrix. If you haven't found it yet a link to my thread is below.

https://www.volvoforums.org.uk/showthread.php?t=302008

There is lots of helpfull advise on the heater matrix from the guys on the forum within the thread. There are also a couple of super detailed descriptions (with photos) of how to replace the matrix on the forum. I think the links are in my earlier thread but if not let me know and I will provide.

If you get a torch and mirror you can peer up under the heater matrix casing from the driver's side and see drips from the low point if it is leaking. I also placed a couple of sheets of kitchen towel on top of the transmission tunnel (push in from the drivers side). If it is leaking you will see antifreeze coloured drips.

I have to admit that I cheated in the end as I ran out of time and added K-Seal to the coolant which sealed the leak within a day and it has been dry for the last 3 weeks. There are differences of opinion on the forum about the use of K-Seal and I may live to regret it but I used it as delicately as I could (see my thread).

Would be keen to hear how you get on as I may bite the bullet myself.

Good luck,
LeeP

[bgarston]

Originally Posted by TheBadger

I have a number of questions, the first is, is there a way of diagnosing whether the the matrix has failed or is there a more simple series of possible issues to look at in the first instance that may save a strip out.

Hello Badger. Welcome to the forum and 940 ownership!

I know from experience the coolant level in the expansion tank will drop over time and you will have had very wet carpets too.

It is as you suggest very likely to be the matrix at fault however it's worth double and triple checking as it's a lot of work to take a matrix out (don't be put off, it is still very much a DIY job) only to find the problem is elsewhere. Take the carpets/sound deadening out and make sure the footwell(s) are dry. Next lightly coat the transmission tunnel with talc. Then go for drive. The coolant on the talc should show up really very well and confirm your thoughts.

In terms of sourcing and changing the matrix good units can be found here: http://www.vehicleheaters.co.uk/ The job of changing the matrix took me ~5-6 hours over an entire weekend to strip out, replace and put back much of the dash and many weeks after trying to wash and dry everything out thereafter! There is a very useful thread here: https://www.volvoforums.org.uk/showthread.php?t=43621 which takes you through the process.

Hope this helps? Best of luck. Let us know how you get on.

Ben

[nutco]

I have to admit that I cheated in the end as I ran out of time and added K-Seal to the coolant which sealed the leak within a day and it has been dry for the last 3 weeks. There are differences of opinion on the forum about the use of K-Seal and I may live to regret it but I used it as delicately as I could (see my thread).

Would be keen to hear how you get on as I may bite the bullet myself.

Good luck,
LeeP[/QUOTE]

Lee, I used K-seal on my 98 940 at 170K, its now on 229K and all still good,