Surprise surprise, it's a heater matrix leak
 

Just finished the 1200km trip to Portugal without any significant issues, but at one of the stops I realised my partner's white sneeker was yellow/green. Went to check the passenger foot area and there it is, a leak. There were just a few drops of coolant on the duct ends and the carpet wasn't that wet, but something is leaking for sure.

I've read a few threads on this, both just now and way before buying the car. I'm aware that it is an involved job, but maybe not really how involved/difficult it is.
A few questions:

1 - Is this mainly a time consuming related thing? Or are there parts that are difficult to take of etc?

2 - Given I live in a hot country and it's summer, can I just bypass the matrix from the side of the engine bay and does this interfere with the AC making cold air?

3 - Besides time (I would do it myself), is this an expensive job in terms of parts? matrix, hoses, etc

To answer your questions:
1 - Is this mainly a time consuming related thing? Or are there parts that are difficult to take of etc?
Not difficult, just time consuming. Should be no problem for someone who managed to change his turbo out on the street... It took me one and a half day. There is only one bolt that is difficult to get to. I bought a simple 1/4" ratchet set and got it out with the extension pieces in the set.

2 - Given I live in a hot country and it's summer, can I just bypass the matrix from the side of the engine bay and does this interfere with the AC making cold air?
No problem to bypass the matrix. I believe you have the version with the heater connections sticking through the bulkhead and a vacuum controlled heater control valve. I just took off the hoses from the bulkhead connection and shortcut the matrix by connecting both hoses, using a piece of I believe 12 mm copper pipe. No problem for the cooling system or AC at all as no warm water will be flowing through the heater, just as if the heater valve was closed.

3 - Besides time (I would do it myself), is this an expensive job in terms of parts? matrix, hoses, etc
No, you just need a new matrix (preferably a Volvo OEM one, as the heat capacity of a Nissens is 30% lower. Might be less of an issue in the region where you live). There are no hoses underneath the dashboard, they are all located in the engine bay.


This description https://www.volvoclub.org.uk/faq/Hea...eplacement.pdf was quite helpful when I replaced my matrix.

Rob

Not difficult, just time consuming.

I replaced the entire heater box in my 740 when converting to ACC from manual non-AC.

The new heater box has a vibration/rattle from one of the internal flaps when the engine is idling.

I live with it, rather than pulling it back out and trying to resolve the issue!

You did this from the engine bay right? Where the hoses connect to the firewall.

QUOTE=Rversteeg;2896892]3 - . There are no hoses underneath the dashboard, they are all located in the engine bay.[/QUOTE]
Not sure if I'm understanding correctly. You mean the pipes from the matrix stick through the firewall, so the only hoses are in the engine bay? Does this mean that my leak must positively be on the heater core itself? No possibility of a cracked or untight hose!?

Its highly likely to be the heater matrix.

Others may confirm this , but if you dont need the heater simply Drain and pull off the two hoses in the engine bay.Connect the ends together with a piece of pipe, bypassing the matrix. At least that way you can be certain that it is, indeed, the matrix.

Matrix
 

On my '98 940 LPT / AC the rigid pipes of the heater matrix stick through the bulkhead. So the pipes you see when you remove the rubber hoses, are actually the pipes of the heater matrix itself. You can be sure that it is the matrix itself that is leaking.

Attached picture of the matrix, encircled pipes stick through the firewall. A new OEM matrix is about 210 / 250 Euro, a Nissens imitation about 50 Euro.

ok, that's what I thought you meant, but I wanted to be sure. Thanks for clarifying.
For now, given it's summer and all, just for the sake of practicality I'll just bypass the matrix, but I might replace it in the winter. I very very rarely turn the heater on. Not only because there is no need, but also my partner hates all sorts of ambient/air heating for some reason. So realistically, I probably would be better not even replacing it at all, since it would be one less part that could fail and no risk of damaging plastics on the dash.

Does the Nissens have fitment issues? I've read of some people having trouble with fitting aftermarket.

The aftermarket are a poor replacement.

Having gone this route a while back I wish I had gone for an original. Depends how cold your winters are there as the heat output is greatly reduced compared to the original,thus,in my opinion, lowering the Volvo standards

There must be something that can be poured into the matrix to seal it without clogging it up.That way you could possibly 'repair' it without spending hours dismantling the front of the interior.

There is another thread that people given several option of these sort of liquids to fix small holes. I might try one, but for now I will just bypass the matrix and although I'm all for taking on big jobs, I kinda know that I probably won't ever replace it. Because I trully never turn the heater on. It's never that cold in central coastal portugal. So once the leak is "fixed" I'll probably just forget about it to be honest.

put a bottle of K seal in the header tank run with heater on for a few miles to circulate and the leak will stop .I did mine 10 years ago and it is still ok.