HOW TO: Check and Remove R75/MG ZT Heater Matrix - MG-Rover.org Forums
 
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post #1 of 18 (permalink) Old 01-02-2013, 19:24 Thread Starter
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HOW TO: Check and Remove R75/MG ZT Heater Matrix

Someone asked for a HOWTO/Walkthrough so thought I'd do one.

Firstly to check if your matrix is working as it should (sort of a flow check):

In the below image you will see red arrows indicating which screws to undo.



undo the screws that secure the under panel (black plastic) and remove the panel. the steering column under cover can be removed aswell to make access easier, this is done by simply pulling it out and upwards (clips hold it in place and are easily pulled out of their sockets).

Once you have removed those panels undo the screw that holds the black plastic footwell vent onto the side of the matrix housing. once removed you can simply slide the carpeted panel down and out.

you should now have good access to the matrix and pipework as below:



it's easy to check if you heater matrix is getting the flow and working correctly now.

We all know how a radiator works, hot water flows in, heats the radiator and heat comes from it by convection/radiation depending on the type. For hot water to flow in water must flow through and out the other end, otherwise the water backs up until it reaches the same pressure as the rest of the system but goes nowhere.

Now, with the engine at normal operating temperature and the heater fans SWITCHED OFF. BOTH pipes should be as hot as each other, because the fans aren't moving air through the fins to cool them so no heat (or very little) is lost through the matrix. In this case your matrix is highly likely to be working correctly (within reason).

If BOTH pipes are COLD then this could mean 1 of 2 things. 1. your heater may have an airlock (though it's unlikely by the design of the water system on the 75/ZT) but in any case it's worth checking it. 2. If it isn't an airlock your matrix is sufficiently blocked so that it allows NO FLOW whatsoever through the matrix and requires removal and specialist attention (see how to remove below).

If 1 of the pipes is HOT and the other is barely warm then there is a substantial obstruction in the matrix but it is allowing SOME flow through it (usually the passenger side is blocked but the driver's side is flowing as it should).

It is a waste of time putting a hose pipe onto the pipe to try and "flush" the blockage through. Why? Because water ALWAYS takes the route of least resistance. If 6 out of the many pipes are blocked the water will simply flow around the blockage (it CANNOT flow THROUGH it). You may dislodge some of the crud/scale that is in the matrix but it will ONLY be from the pipes that are still allowing flow through them.

Now to the HOW TO part:

Do as above & remove the panels to gain access to the matrix and pipes.

Make sure to remove all the coolant from your system before removing the matrix.

You will see in the image below an arrow next to a piece of black "sponge-like" insulation, this covers the air conditioning pipes from heat soak. Behind this black insulation is a bracket securing the aluminium pipes to the matrix, remove the screw and bracket. You can do so by going behind the clutch pedal with a phillips screwdriver (fiddly but easy enough).







Now you have done that it's time to remove the matrix. The image below shows the pipe collars that hold the main pipes to the matrix. Have something ready to catch the water that is left in them. Undo the screws and pull the collars to one side (you can leave them on the pipes). Pull the pipes apart enough to let the water drain out. once the water has drained and your ready to remove the matrix you can release the pipes completely by pulling the right hand side pipes further right - they will move and maybe even bend slightly but don't worry they'll go back together easily enough. You can turn the pipes that go into the matrix slightly to make it easier - you won't damage them unless your rough.



Now that the pipes are free you can simply get hold of the matrix and slide it out towards you, don't twist it as it will jam.

Once you have it removed take it to a radiator specialist and they will clean it properly.

Hope this helps

Last edited by shambo; 01-02-2013 at 19:37.
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post #2 of 18 (permalink) Old 02-02-2013, 10:02
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Acting the Devil's advocate here, a couple of questions:
Quote:
Originally Posted by shambo View Post
Now, with the engine at normal operating temperature and the heater fans SWITCHED OFF. BOTH pipes should be as hot as each other, because the fans aren't moving air through the fins to cool them so no heat (or very little) is lost through the matrix. In this case your matrix is highly likely to be working correctly (within reason).
If the passenger side is silted up, there will still be full flow through the rest of the matrix. So wouldn't both inlet and outlet pipes be equally hot anyway? How is the diagnosis of a blocked matrix made by comparing the pipe temperatures? I'm using your path of least resistance argument against flushing through with a hosepipe. Whether that is successful really depends on how compacted is the debris. Lots of members have successfully hosed through the matrix and regained heating on the passenger side. Some haven't of course and one regular factor is the previous use of a leak sealant in the cooling system. Blockages from a sealant are unlikely to be easily shifted by any method. Taking the matrix to a radiator specialist for cleaning out isn't a widely available option I suspect. However, I'd be interested to know how they do it.

Have you any photos, advice on reconnecting the pipes? Most people seem to find that removing the matrix is pretty straight forward. It's getting it all back together where the problems start. Several reports indicate that joining the stubs together with rubber hose and Jubilee clips is preferred rather than struggling with the clamp collars. Did you find reconnecting the O-ring clamps easy?

TC

Last edited by T-Cut; 02-02-2013 at 10:12.
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post #3 of 18 (permalink) Old 02-02-2013, 10:10 Thread Starter
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if the matrix is semi blocked (passenger side as usual) it doesnt get full flow so the flow is slowed through the pipes and matrix and heat is lost due to the loss in flow (water spends more time in the matrix so loses heat.

To clean the matrix properly they will remove the bottom or top plate (by cutting it off) then road the pipes to clear them. test flow and weld the plate back on.



I found it fiddly but easy enough to re-connect the clamps and pipes yes. as long as your not too rough taking it apart it goes back simple enough.
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post #4 of 18 (permalink) Old 02-02-2013, 11:04
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I've found if a blocked matrix is flushed you get debris in the flush somewhat like cooked rice, if the car has had thermostat re work, then you may see bits of black plastic and finally K seal if that's been added then the whole system holds on this devils elixir and really does take some shifting.

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post #5 of 18 (permalink) Old 02-02-2013, 11:36
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Quote:
Originally Posted by shambo View Post
if the matrix is semi blocked (passenger side as usual) it doesnt get full flow so the flow is slowed through the pipes and matrix and heat is lost due to the loss in flow (water spends more time in the matrix so loses heat.
But the inlet flow rate equals the outlet flow rate, so the pipes remain at the same temperature whether there's a partial blockage or not. Temperature isn't heat.

TC
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post #6 of 18 (permalink) Old 02-02-2013, 19:16
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thanks for the how to.
haveing problems with my heater at the moment.
been in and had it cleaned out and all seems ok.
day one from when it was done all ok. loads of heat from drivers side. and a fair bit of heat from passanger side.
day two a drop in temp on drivers side and just warm on passanger side.
day three drivers right down and passanger side not much heat at all.

as i was playing around with temp controls turned them both down to low.
drivers side was blowing out stone cold but passanger side was not blowing out as cold as the other side.

as far as i can see the temp control on the passanger side is working ok.
i wonder if the temp controls can be adjusted and this just needs adjusted due to old age.

thanks all
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post #7 of 18 (permalink) Old 02-02-2013, 22:12
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The two-side temperature control is simply based on mixing hot air and cold air by the adjustment of baffles/flaps in the ducting. The heater should supply the hot air and the refrigeration system the cold air, if a below ambient flow is needed. There's no connection between temperature settings and the actual temperature of the heat sources (the hot and cold matrices). I don't know if that answers you query.

TC
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post #8 of 18 (permalink) Old 02-02-2013, 22:41
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thanks tc.
both me and the garage cannot understand why one day all works well.
then it goes down hill.
dont know if i should go down the line of a new matrix or go down the line of takeing the whole lot out and checking all the flaps

thanks steve
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post #9 of 18 (permalink) Old 06-02-2013, 13:14
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Quote:
Originally Posted by notlongnow View Post
thanks tc.
both me and the garage cannot understand why one day all works well.
then it goes down hill.
dont know if i should go down the line of a new matrix or go down the line of takeing the whole lot out and checking all the flaps

thanks steve
The matrix was blocked by some crud in the system. You had it cleaned but there could still be lots of what blocked it in the first place still circulating and has done the same thing again as you say it SLOWLY blocked up.

Could be a flap problem but why should that manifest itself SLOWLY ??

You didn't say if the whole system was cleaned out when you did the heater rad.

I think the matrix is blocked again. Sorry.
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post #10 of 18 (permalink) Old 27-01-2015, 11:45
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Quote:
Originally Posted by T-Cut View Post
But the inlet flow rate equals the outlet flow rate, so the pipes remain at the same temperature whether there's a partial blockage or not. Temperature isn't heat.

TC
If there is flow of heated water into a heat exchanger loss of heat occurs.
The more efficient the exchanger the greater the heat loss.

Our measurements conclude that heat loss in a brand new Matrix (ie max flow) is greater due to it's efficiency in dissipating heat.
We have measured up to 5 deg difference between inlet & outlet.

In a partially blocked matrix the difference between the inlet outlet is typically only 1 - 2 deg C

Obviously there's a point where no flow happens in a totally blocked matrix.
In which case the outlet and inlet temp will be very low (due to no circulation to & from engine)
ie: approaching or at the ambient cabin temp instead of typically 55 - 70 deg C

All the above assumes normal functioning thermostat at operating temp.
Figures will vary also depending on ambient cabin temp
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post #11 of 18 (permalink) Old 27-01-2015, 12:20
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Quote:
Originally Posted by julian View Post
If there is flow of heated water into a heat exchanger loss of heat occurs. The more efficient the exchanger the greater the heat loss.
Agreed, but I was simply applying the no heat loss supposition made by the OP. He said:

Quote:
Now, with the engine at normal operating temperature and the heater fans SWITCHED OFF. BOTH pipes should be as hot as each other, because the fans aren't moving air through the fins to cool them so no heat (or very little) is lost through the matrix. In this case your matrix is highly likely to be working correctly (within reason).
That's technically incorrect, but near enough when using your fingers as a thermometer.

Quote:
Our measurements conclude that heat loss in a brand new Matrix (ie max flow) is greater due to it's efficiency in dissipating heat.
We have measured up to 5 deg difference between inlet & outlet.
In a partially blocked matrix the difference between the inlet outlet is typically only 1 - 2 deg C
Clearly, heat is lost even without an air flow through the matrix, but I doubt any of the temperature differences noted could be detected by touching the pipework with your fingers, which is what the OP was describing.

Thanks for your additional data.

TC
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post #12 of 18 (permalink) Old 01-12-2015, 23:22
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Hi Shambo. Can you send me the guide for remove heater matrix? I don't see the images in the first page. Thank you
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post #13 of 18 (permalink) Old 02-12-2015, 11:41
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Flap test

Here is the link for performng the flap test.

http://www.the75andztclub.co.uk/foru...d.php?t=162975

I have successfully unblocked assorted heater matrix s over the years by filling them with neat kettle descaler, leaving
for several hours and then flushing with a hose. It is remarkable what happens when you have flushed it until it runs clean
if you then reverse flush it, it will usually come out filthy again!

Last edited by wuzerk; 02-12-2015 at 11:50.
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post #14 of 18 (permalink) Old 02-12-2015, 13:58
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I don't see any need for removing the matrix. Disconnect the inlet and the outlet rubber hoses, and flush it in situ.
You should run water both ways through the matrix, and it might even be beneficial to use compressed air carefully to speed things up a bit.

I did, and it worked a treat.
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post #15 of 18 (permalink) Old 12-03-2017, 18:57
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Holy thread revival!!!!

I've notice this thread and a load of others have now got missing pictures.

Has anyone got the pictures that should go with this thread?
My heater takes forever just to get luke warm, and over 30 mins to get warm-hot.
I think heater matrix either needs Bleeding? if its like the TF which has a bleed point at the heater matrix or is blocked/full of crud and needs flushing.

Has anyone got either the pics showing how to remove or flush a heater matrix in a ZT/75 or another linky to another how to that still has pics.

Ta.

P.s.
computer Nerd Types, is there not some way that peeps can make posts and the pics dont dissapear over time?
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post #16 of 18 (permalink) Old 13-03-2017, 06:33
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... is there not some way that peeps can make posts and the pics dont dissapear over time?
Forums are hosted on servers with limited amount of disc space. Because of that it is not allowed for each Registered user to upload pictures on the site as disc space would soon become non existant. Buying new discs in order to enlarge space only for pictures is not economicaly viable.

Uploading of pictures is allowed only to Supporters and within this privileg you still have limitations in regard not to waste disc space.

Because of all of this members open account on one of pictures hosting sites, upload pictures there and post links here in the forum in order for poctures to be seen.

Problem is, when members stop posting or loose interest in forum, they usualy do not upload pictures to pictures hosting site, forget abojt them, and these sites, again in order not to waste disc space, delete dormant account after some defined period of time.

In such way pictures are inevitably lost.

Only way how you can save the pictures is to copy them to your computer, or make pdf documents from these threads. However, in order to do so on each thread over time you would need some for of chronicle person who would take care of such things.

Unfortunately these kind od persons does not exist that much and because of that some things are lost until somebody else do not decide to make new pictures.
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post #17 of 18 (permalink) Old 15-03-2017, 13:21
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Thanks for the reply roverlike, sorry for late reply been busy with new house.
Do you or anyone else know/be able to tell me where the inlet and outlet pipes for the matrix are loacted? On the TF they were accesible in the frunk.
Is it/are they in the engine bay or in the cabin?

Ta
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post #18 of 18 (permalink) Old 15-03-2017, 17:04
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Is this picture of any help?



The other side of the pipes obviously goes to engine bay compartment.
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