Removing rear AC... suggestions?

Furi · Post by **Furi** » Mon Sep 26, 2016 2:20 pm

I'm in the process of removing the rear AC; have all the controls and wiring out of the cabin. Next would be to remove the compressor, etc. from under the car. I've seen that there is a coolant line going into the AC and one coming out which is just looped back once the AC is removed. I've been reading some posts as well as the excellent workshop manual (thanks Growlerbearnz and Motorang) and it seems that I would need to empty the coolant and refill once the components are removed and the hose reconnected. Anyone know of a trick which this wont be necessary? i.e. having to remove/refill coolant?

Post by **Growlerbearnz** » Mon Sep 26, 2016 9:09 pm

I don't know of any tricks which will allow you to remove the rear unit without losing refrigerant. There aren't any valves to close to seal that part of the system off. I'm curious to know how you're planning on sealing the rear pipes- some kind of special bung that screws onto the pipe ends?

As for draining the refrigerant, yes, you absolutely should have it drained by a refrigeration service centre, so they can dispose of it correctly. Our aircon systems use the old, evil R-12 (freon-12) which destroyed the ozone layer and gave my Mum skin cancer.

In case emotional blackmail isn't enough to sway you

a refrigeration service agent will also flush* out the lines, removing the old oil. When you have the system recharged they'll be using R-134a refrigerant, which is incompatible with the old mineral oil. They'll install the correct amount of refrigerant and the correct amount of PAG oil to suit. They should also fit a new receiver/drier so your aircon will continue working for years to come.

*Originally I said "vacuum", but that process just removes the air, not the oil. Thanks to Tractortech for pointing that out!

Furi · Post by **Furi** » Mon Sep 26, 2016 9:51 pm

I am definitely planning on having a shop drain the refrigerant out of the AC. The Ozone hole is just starting to get better....

But to be clear I was referring to the Engine Coolant. Wanted to see if it would be possible to remove the AC unit without having to drain it and fill it back up again after removal. Attached pic for reference from http://www.mdocuk.co.uk/forums/viewtopi ... sc&start=0.

I am assuming the hose on the left side is connecting the in/out to the unit of the Engine Coolant and closing the loop.

: RearACRemoved.jpg (221.57 KiB) Viewed 7592 times

Post by **Growlerbearnz** » Tue Sep 27, 2016 3:39 am

Oh! Apologies. I got confused when you said AC where I'd say heater. Yay regional language variations!

Trick for removing hoses without losing too much coolant: pinch off/fold the small rubber hose that goes between the radiator and the overflow tank. That'll create a vacuum and stop too much coolant falling out when you disconnect the rear heater hoses. You're still going to lose some, so put a bucket under the hose connections when you remove them.

That picture is exactly what you think it is. I'm not a huge fan of folding a hose like that (it can damage the reinforcing fabric inside the rubber hose, leading to a leak later), but it works. I'd plan on eventually removing the rear heater steel pipes entirely, and connecting the front heater directly to the engine block- just like a van without a rear heater.

Furi · Post by **Furi** » Tue Sep 27, 2016 8:30 am

Exactly the kind of info/insight I was looking for; thanks a bunch. Would there be any air in the Engine Coolant system that needs to be burped out after the in/out pipes are connected and Coolant lost is replaced?

The kink in the hose bugged me too. I'm actually hoping to reuse that coolant flow and put through a water tank in that location to have hot water after a drive; or idle the engine for a few minutes and have a hot shower :) At first I thought I had to to do the whole thing in one shot; remove AC/Heater and install watertank, due to the concern over the Engine Coolant. Now I might be able to get away with doing it in stages.

Post by **Growlerbearnz** » Tue Sep 27, 2016 3:17 pm

The L300 coolant system isn't known for trapping air- just set the heater temperature to hot before running the engine the first time and any air bubbles should migrate to the radiator pretty quickly. You may need to add a bit of coolant to the radiator after running the engine for a couple of minutes, but that's about it.

I understand that L400 rear heaters are notorious for having air locks when drained.

Furi · Post by **Furi** » Wed Sep 28, 2016 6:40 am

Thanks again; great insight. To clarify; you mean to run the blower before starting the engine? Or start and let the engine idle while running the heater for a bit?

Post by **Growlerbearnz** » Sun Oct 02, 2016 2:37 pm

Just make sure the temperature knob is in the hot position the first time you run the engine. That opens the heater's water valve and lets water circulate through the heater circuit, pushing any air bubbles into the radiator. No need to run the blower.

speleokip · Post by **speleokip** » Mon Oct 03, 2016 8:24 am

Use a small F type quick clamp on heater hoses by left front wheel. That way you can act like a surgeon clamping off the bleed.

Furi · Post by **Furi** » Mon Oct 03, 2016 10:39 am

so I can finally say; I'm not a mechanic but I play one on TV!!

Thanks both. Good pointers.

Furi · Post by **Furi** » Fri Oct 07, 2016 10:25 am

couple of other questions... is the coolant flowing through the rear heater all the time or is the coolant flow turned on/off by the heater controls?

And assuming that I wanted to splice into the rear heater coolant in/out pipes with a copper pipe, what size pipe would be sufficient so not to effect the flow of the coolant. The in/out coolant connections for the back heater are pipes before connecting to hoses so that might be a good indication but wanted to make sure.

Furi · Post by **Furi** » Fri Oct 28, 2016 2:50 pm

Is the coolant flowing through the rear heater all the time or is the coolant flow turned on/off by the heater controls?

I touched the in/out coolant hoses for the rear heater while the car was on for a while and the popes felt warm to the touch but not very hot.

Post by **Growlerbearnz** » Sat Oct 29, 2016 1:11 pm

It's only the current pope that's slightly warm, the previous ones were cold.

From memory the rear heater has a valve that (mostly) shuts down coolant flow when set to cold. Try setting the rear controls to hot and see what happens.

Furi · Post by **Furi** » Sat Oct 29, 2016 1:33 pm

hah! :) I do like the current pipe much better than previous pipes....

Setting the rear control would be a little difficult as I have taken them out already :) And not exactly sure at what setting it was when I took it out. Any other way to trigger that valve?

Post by **Growlerbearnz** » Sun Oct 30, 2016 3:03 am

Oh yeah. That probably makes things a bit trickier. I'm not even 100% certain there *is* a valve- I've not had the rear heater apart quite that far. Yet.

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