Mmmmm, the sweet smell of hot coolant in the HVAC vents.

Am I looking at a leaking heater matrix?? Carpets not wet (there anyway!) yet.

Take the drivers side panel off the centre console and have a look. If it's coming from the O rings, a relativity simple and quick job, if it's coming from the bottom of the vent, it's a dash out job.

Will do, got a long trip to do first so hope it holds up.

j_rov wrote:

Will do, got a long trip to do first so hope it holds up.

I would take some suitable bits with you to do a roadside matrix bypass just incase.

and wear wellies!

Ho Hum… I was prepping my car for it’s overdue MOT. Parked in the sunshine, opened the driver’s side door, and noticed some little ruby-red drops glistening on the carpet….. After all I’ve been through recently I wasn’t a happy bunny.

How “robust” are the matrices really? This car is 22 years old, but only 78k miles. Is this liable to be a simple O ring job, or is it usually 50/50 whether it’s the matrix too?

Contemplating cancelling the MOT test (Wednesday) because I won’t get the parts in time. I’d hate to ‘chance it’ and then find the car stranded and needing recovery. Guessing the ‘matrix bypass’ is just a U bend of 19 or 21mm pipe, and that this gets done in the engine bay?

How long would a ‘drippy’ situation last? For all the use I’ve given this in the last few months (or year) it might have been leaking for ages, and it’s just that it caught my eye this time in the sunlight.

Off to research O ring and matrix changes.

At the age it's almost certainly time for a new pair of O rings. Only get the genuine LR ones, for the sake of the minimal extra cost it isn't worth saving a couple of quid. You'll need a long (300mm) number 2 pozidrive screwdriver. It isn't difficult just fiddly, see https://web.archive.org/web/20180530141620/http://www.rangerovers.net/repairdetails/heateroring.html.

Heater cores tend to only fail after someone has changed the O rings and got brutal with the screw and cracked the matrix. Yes, matrix bypass is just linking the in and out under the bonnet and leaving the pipes through the bulkhead open.

Biggest problem with leaving it dripping is the inch of foam under the carpets. That soaks up the coolant and it just stays there, taking the carpet out to dry it out isn't a fun job.

Thanks Gd,
Lots of good reading on those links. I’ve already made an order for the genuine O rings.

Reading that, and other stuff it occurs to me that the O ring seal was probably disturbed when I was fighting with the heater pipes in the engine bay, doing the head gaskets - and it’s barely done 10 miles since then…..

Another consideration is that I am planning a carpets and seats swap but I really wanted just a few months where I could drive the thing before getting stuck into the next job…. so O ring change is definitely the first step and see if that can get me the couple of months of fun/reward that I think I need right now.

Absolutely correct, heaving on the hoses under the bonnet will almost certainly cause the, already hardened, O rings to crack and start to leak. The clamp doesn't clamp them tight but holds them in place while allowing a small amount of movement so the flexibility of the O rings keeps the seal. I changed mine when I first got the car and they aren't leaking nearly 12 years later so you'll get more than a couple of months.

This is a link for replacing the o rings not long put up. Is done on a Lhd model but hope it helps.
https://youtu.be/MQ6NJ7F9ths

On that video he puts gloop on the O rings but RAVE says to just dip them in antifreeze. I don't suppose it makes much difference until someone comes to try to change them in a few years time.

Useful video, thanks - particularly as it’s some nice ‘high res’ images of the pipes and matrix.

Whatever you might put on the O rings would have two purposes surely - 1 not to degrade the O ring compound and 2 - allowing that little degree of necessary flex and movement.

Does RAVE say that a dab or red HOAT coolant is OK? Would a dab of silicone grease not do the same thing?

I can’t say I’m looking forward to it, but it’s obviously the access problems rather than the technicality of the job itself.

in the event that the screw dosen't come undone you can drill the head of it with an extra long drill bit , its usually the back of the screw that goes rusty and will not come undone , you will have to remove the pipes then to extract the screw from the plate

A thin smear of silicon grease is probably OK although I just dipped my o-rings in coolant as per RAVE when I did mine a few weeks ago. Do not be tempted to use any other gloop unless it’s the type that never dries and remains flexible for years as it a sure fire way to get leaks in the short term - those pipes need a little bit of flex during their life time.

Soak the back end of the screw with plenty of penetrating oil and leave it to do its work. Use the correct screwdriver - this is an absolute must. Crack the screw by tightening it very, very slightly before undoing (too much tightening risks cracking the plastic matrix). Once the screw is moving unscrew a turn then screw up half a turn and continue doing this until it becomes easy to unscrew or is completely unscrewed - this out in action allows the threads to clear themselves of any built up crud on the back of the screw rather than drawing it right into the threads and risks seizing everything up. Be patient about removing the screw - half an hour of patient work here can save hours of heartache later! I have not seen anyone say they have successfully drilled out the screw without removing the dash!

I was lucky and got the screw out without damaging anything. I replaced it with an allen head stainless steel screw.
I used silicone grease on the (LR genuine) o-rings. Must be 10 years + now and its been OK since.

Some comments on the video posted above:

1. It’s a LHD vehicle so for a RHD vehicle the steering column is rather a large impediment to getting a good view and access.

2. When the centre console side panel was removed it is clear that someone had been in there previously and removed a huge portion of the plastic dash underneath. Without that removal cutting of the ducting as he did is not possible although it did offer good access to the screw head. Most of us just drilled some holes in the appropriate places.

3. The use and amount of sealant he utilised may well prove to be counterproductive! Not something I would do or recommend. It’ll be a bugger of a job if he has do do it again at some time!

Also, dip the tip of the screwdriver in valve grinding paste so there is much less chance of it riding out and damaging the screw head.

As a plumber I used a little silicone grease on the o rings same as I would some boiler parts.

Well, my O rings aren’t supposed to be here until Thursday or Friday, but I thought I’d just get on with it. If nothing else, the sooner I can get some plus-gas on the screw head the better, and the more likely it will behave itself.

I didn’t quite get that far, but I did get to the point where I now need to drill the hole to access the ‘secret screw’. As it’s my first time at this, and wanting to make it as stress free as possible for myself, I removed more of the stuff in the centre console to get some visibility in there (HEVAC, radio, and switch/surround). Only a few more screws and multi plugs, and I feel that I have a much better idea what’s ahead.

Tomorrow I’ll hopefully get the heating ducting removed and some plus-gas on the screw. I’ll leave that to do it’s stuff until the O rings are here.

I have at least got a glimpse of the matrix where the pipes and O rings are, so it’s no longer some hidden, mythical thing. Lots of red coolant around there too. Before I clean that off I’m going to see if there’s any evidence of it having come from the matrix itself, as opposed to the O rings - but I am banking on the O rings themselves.

Thanks for all the help.

Wet vac is useful and a dust sheet