Remove pipes from heater matrix D4

**Bananas** · 5th November 2023, 11:21 AM

Hello everyone
I have a 2010 Discovery 4 with, what am am almost certain, is a partially blocked heater matrix. I have some heat, more on the passenger side, less on the drivers side.

If I am unsuccessful flushing the blockage out does any one know if the swaged on pipes can be removed from the current matrix so I can leave the pipes in place and not be forced to remove the dash? If this is the case, can the existing pipes be fitted to a new matrix in place and clamped with clamps or by folding the housing material of the new matrix over the pipe flanges? Is this normal practice?

I've highlighted the 4 little swage folds holding each pipe in place in the attached photo. It looks easy enough to unfold these with a flathead screw driver.

I think the matrix is the original one with the pipes permanently fixed and continuous all the way up to and I assume through the fire wall. I've had the centre console and centre dash with the side kick panels out (and now back in again) and I'm hoping to avoid further dismantling.

I flushed a fair bit of sediment out using a little gear pump passing hot water in through one pipe and out through the other, reversing this a few times. Pressure in the system would have only been due to pack pressure and although I didn't have a gauge on it, it would have been low. I'll try again at the recommended pressure and with a suitable coolant flush.

Thanks very much.

**p38arover** · 5th November 2023, 12:42 PM

I suspect you have a different problem. It would be a single heater core for both sides and heat would be controlled by blend flaps, one each side.

These days, the heater works all the time and temp control is done by blending cold air with air from the heater. I don’t know how the D2 does temp control but I suspect I’m right.

**PerthDisco** · 5th November 2023, 09:06 PM

The answer is yes others have swapped the matrix and reconnected the pipes. Matrix does block up from far end.

**BradC** · 6th November 2023, 02:14 AM

Originally Posted by p38arover

I suspect you have a different problem. It would be a single heater core for both sides and heat would be controlled by blend flaps, one each side.

Possibly. A cold passenger side is an indicator for a blocked matrix. In the D3/4 they use a parallel flow core fed from the drivers side. Over time the passenger side of the core acts as a coolant filter and progressively blocks up with grunge leading to "cold wife syndrome". While there is one core for both sides, the air flow is such that there's little crossover between sides and the core is effectively half and half.

To have heat on the passenger side and not drivers side is not characteristic of a blocked core, but as you say blend motors. Not saying the drivers side won't block up first, but given the water flow I'd say it's incredibly unlikely.

**veebs** · 6th November 2023, 12:22 PM

Is pre-emptively flushing these cores something anyone has ever done? I figure better chance of cleaning it out whilst there is still some flow in there right?

Is it, 'easy'?

**Bananas** · 6th November 2023, 01:01 PM

Thanks very much.
I will certainly check for errors indicating the blend door motor(s).

In my original investigation I removed the centre console and centre dash which was easy enough, then seeing that the pipes were crimped on I figured I should go back a step and try a flush before committing to the steering, instrument cluster and dash. Prior to beginning there was very little heat coming out with the heater on full tilt.

A little back story for reference: the car was owned by my Dad who has maintained it well and has put about 350 k on it with lots of trips. Apart from this, a knock in the steering noticable when changing direction at low speed and a bit of front diff noise above 120 km/h I'm feeling pretty lucky (I'll address those next). He has a new vehicle now so I scored this one. His trouble with the heater followed plugging a slow weeping coolant leak with an aluminium silicate leak stopper. The weeping leak was cured and the temperature gauge happily sits in the dead centre of the display.

My flush setup is shown below but before I hooked up the pump I blew on one of the braded hoses till my ears hurt like if you try to blow up one of those long balloons used to make balloon animals. Eventually i heard some gurgling and the fluid in the cup shown below came out. I strained this sediment out - if you guessed that it sparkles in the light, you have guessed right. After no more fluid came out I ran the pump with about 70 deg C hot water circulating around for yonks. During this time I could feel the pipes and core end cap become very hot to touch. I regret not feeling whether or not they were hot to touch with the engine running prior to beginning.

I'm guessing I created a clear path or paths on the passenger side but the driver side paths remain blocked.

I put it all back together and now have warm air on the passenger side and slightly warm on the drivers side. An improvement and a vote in confidence that the issue is more likely to be a blockage than blend door motor.

I looked at crimp tools online for this type of job but access is pretty tight so that might not be an option anyway. Perhaps folding the housing on the new core over the existing pipe flange with a suitable flat punch will do the trick. Has anyone seen a post where someone has had success with this?

Perhaps clamping is another option if the mating parts are compatible as is cutting and joining new and original pipes with heater hose as I have read folk have done. Taking the dash out is still an option too I guess.

Sorry for making you rotate your head or monitor for these:

72075840078__72615CA2-E004-4C74-A90B-734F27958DB4.jpg IMG_3479.jpg IMG_3480.jpg 72077494762__5AA53646-B6ED-4CBA-8899-8FBB7DC93126.jpg IMG_3487.jpg

Thanks again.

**BradC** · 6th November 2023, 07:14 PM

Originally Posted by veebs

Is pre-emptively flushing these cores something anyone has ever done? I figure better chance of cleaning it out whilst there is still some flow in there right?

Is it, 'easy'?

D3 grunge in the coolant bottle

Easy is one of those relative words. Easier than replacing the core anyway.

**Bananas** · 6th November 2023, 07:46 PM

I found this...

Heater core change with out pulling dash | Lexus IS Forum

Looks 'easy'

**Bananas** · 6th November 2023, 08:21 PM

Originally Posted by BradC

D3 grunge in the coolant bottle

Easy is one of those relative words. Easier than replacing the core anyway.

That's a nice air/water rig. I'll try that before bending things. Thanks.

**Bananas** · 12th November 2023, 12:10 PM

Back for round 2 this weekend. Still with no obvious problems identified.

I dropped the coolant again and rigged up compressed air and water similar to BradC's rig. Flushed heater core again till it was running crystal clear. A small amount of sediment came out but hardly any really.

Vac purge and refill then drove the car to temp. No improvement on either side. Passenger side still warm (not hot) and driver side with only a hint of warmth.

I tried the manual blend motor recalibrate (A/C and recirculation buttons pushed while turning the ignition on). No change.

So I removed the console and centre dash again and stretched the plastic frame under the steering wheel out so I could remove the driver's side blend motor. With the motor removed but hanging on it's wires I can see the white actuating arm to move by adjusting the temperature (I have reinstalled the 2 key fob transponders, ignition button and climate control panel).

With the blend motor removed I can rotate the blend door easy enough by grabbing the splined drive thingo, full open to full closed. I hear the door thump at each extreme. This is also through about 90 deg.

I've put the motor back in and I can see the white arm moving in the same manor as described above. At 24 on the LCD the arm is full travel down (corresponding I guess with the heater door closed), at 25 on the LCD the arm rotates forward toward the firewall by a few degrees, at 26 it rotates more, 27 rotates, 28 rotates, then at HI it is pointing at the firewall (corresponding I guess to full open).

I've compared this with the passenger side and it has the same behaviour.

So I'm assuming the blend motors, blend door and control system are working.

I assume this is normal?? Engine is cold and it's an pretty damn warm day.

BTW: What a total PIA removing the third screw holding the motor in!!!! 2 hours of yoga and trying every tool I own before a cup of coffee, a trip to bunnings to buy a junky little Trojan right angle ratcheting screwdriver. NEW FAVOURITE TOOL. Similar to a screwdriver bit in a small socket ratcheting handle but it has just the right geometry for this job.

So, I'm buggered. It's all going back together now. Perhaps I've shamed it in to working.

So after hoping for duff blend motors and seeing them appear to be working I still suspect the matrix. I guess it's possible to have a single clean tube and all others blocked hard.

Does anyone have any other suggestions? Or do I just get the big boy trousers on and commit to changing the heater core?

Thanks!

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