E51 E51 Aircon Pipe Corrosion (Rear)

[Mark76e]

if i remember correctly they are double skinned

That will explain the price and shut me up then!

 

[LeStempy]

True, they are a coaxial pipe so the gas goes up the inner pipe and back down the outer pipe. Someone ingenious could probably make up a twin pipe conversion.

 

[Bob Edwards]

someone made the originals

 

[cjholding]

The factory pipe is coaxial (low pressure around the high pressure) which is probably beyond hand tools.

 

[LeStempy]

someone made the originals

Some machine made the originals.

 

[George322]

I've recently had the blank from Brian (BMR) fitted after more than a year without being able to use the aircon because of the leak at the rear.
The mechanic said it was easy to fit.
I took it for a re-gas and they tested for leaks and re-gassed with 0.6litres and I drove home in comfort on a day where the temp was nearing 30.
A week later and all is well.
Thank you Brian.
The local aircon "specialist" backheeled the job because he said it would lake far too long to do because he would have to remove half the engine and then he'd have to make a blank....
Lazy Wassock!

 

[Shepcobain]

The Elgrand I have just bought has had the rear blanked. I wonder why it costs so much to fix?

 

[Mark76e]

The Elgrand I have just bought has had the rear blanked. I wonder why it costs so much to fix?

Because the pipes are very non standard and basically, a pipe within a pipe.

 

[Tim C]

The Elgrand I have just bought has had the rear blanked. I wonder why it costs so much to fix?

Because you can't use second hand pipes due to the weird connections. And a new one is over £1000 from Japan, because it's from a car that stopped being made 10 years ago.

 

[Shepcobain]

Because you can't use second hand pipes due to the weird connections. And a new one is over £1000 from Japan, because it's from a car that stopped being made 10 years ago.

ahhh, I see. So, you can't get them off the shelf anymore? I'm surprised nobody made aftermarket/copies.

 

[Tim C]

ahhh, I see. So, you can't get them off the shelf anymore? I'm surprised nobody made aftermarket/copies.

Unfortunately it's not a part that was ever available in the UK, it's a very complex part, and twin Aircon setups are very rare. Putting the joints behind the back wheel in way that promotes galvanic corrosion is a stupid design flaw too. Some people say they can fix them, but the fact that nearly everyone blanks it off like yours when it fails tells you how easy it is to do! To be honest it's probably the only thing on my Elgrand that hasn't broken yet.....

 

[cjholding]

If you really wanted to fix it you could probably get an air con firm to run two pipes, rather than the original concentric one, as there are individual high and low pressure connections at either end.
But I doubt it would be cheaper than sourcing the genuine part.

 

[Lpgc]

I've fixed the rear aircon on both of my Elgrands. Both had leaks in the usual position at the rear.

I fixed them by buying second hand but good (no leaks) aircon pipes from @stevemen and replacing the entire front to rear dual concentric pipe.

On one of them this involved lowering the rear axle... You cannot thread the standard single section dual concentric pipe over the rear axle (where it has to be routed) without lowering the rear axle. It isn't too difficult to lower the rear axle subframe, you only have to lower the passenger side anyway (not completely take it off but do slacken the drivers side). I even use the same technique (lowering the rear subframe) to change rear springs because I reckon it's easier than messing about with spring compressors.

On the other one I managed to buy a multi-section (splits just forward of the rear axle) dual concentric pipe from stevemen, meaning I didn't need to lower the rear axle to fit it (due to being able to disconnect the sections it allows routing over the rear axle without having to lower it) but the split section pipes are rare and cost a premium even from a vehicle dismantler.

Before replacing pipes I tried to aluminium weld them and to braze them... It is only the outer section of the dual concentric pipe that usually suffers the galvanic corrosion... But due to the pipe being worn very thin due to the corrosion the aluminium welding and brazing proved impossible, it ended up just making a big hole in the pipe. This isn't to say that a very skilled aluminium welder / brazer couldn't have managed it, but even if they could manage it they would likely need it removed from the car before they could work on fixing the pipe anyway... and if you're removing the pipe from the car you might as well fit another (known good) pipe. Even if a welder/brazer could fix the pipe in-situ you would need to disconnect the pipe at the front end to flush it (remove all the pag oil etc) before the work and again after the work.

Some people reckon they managed to fix leaks on the dual concentric pipe using a variety of products such as 'instant metal', epoxies, etc, in combination with wraps such as fibreglass matting, metal/mesh matting, a piece of aluminium pipe split down it's length.

If anyone else intends on replacing the dual concentric pipe I would advise to first make sure that they can disconnect and reconnect their existing pipe from the rear evaporator... On one of mine when I tried to undo the bolt that secures the pipes to rear evaporator the bolt sheared, so I had to also change the rear evaporator. A lot of people might be prepared to go as far as changing the dual concentric pipe but might not want to go as far as changing the rear evaporator, in which case it would better to make sure they can properly disconnect the dual concentric pipe without effectively breaking the rear evaporator before buying a replacing pipe.

 

[Lpgc]

If you really wanted to fix it you could probably get an air con firm to run two pipes, rather than the original concentric one, as there are individual high and low pressure connections at either end.
But I doubt it would be cheaper than sourcing the genuine part.

That would be possible... But the problem is the fittings at the ends of the dual concentric pipe.

The rear fitting (as it connects to the rear evaporator) is a fairly standard setup over the last 6inches.. the dual concentric pipe splits to 2 separate pipes just before it enters the rear evaporator (the 6 inch pipes) and there are the usual 2 pipes held into the evaporator using a single securing clamp. So there's nothing at the rear end to prevent connecting 2 separate pipes.

But the front end is a design opposite to the rear end, 2 pipes from the under-bonnet AC system terminate at a connector block that is designed to connect to the dual concentric pipe - To run 2 pipes to the rear would have to involve cutting the 2 pipes from the engine bay before they reach the connector block and then connecting those 2 pipes to your 2 new pipes... The problem with using 2 separate pipes is the special connector block at the front that is designed to connect straight to the dual concentric pipe setup, if it wasn't for that we could probably get flexible pipes made up with connectors at each end designed to connect to the rear evap and the front connector. I did think about cutting the special connector off at the front and getting 2 pipes made up (or make them myself, see if I could find a terminator for the rear and some way of joining pipes to the cut-off open pipes at the front) but all things considered it seemed to make more sense just to replace like with like and not need to get involved with cutting and joining pipes or putting end-fittings onto pipes to connect to the rear evap.

 

[brent hayes]

I cleaned mine degreased with brake cleaner, sanded the surface with 500 grit, degreased again sealed hole with slow setting araldite and wrapped with cling film , been good for many many years.

 

[Cainey]

This is not necessarily a common problem, but it happens more than it should.

The problem hear is that the Aluminium Aircon Pipes that run to the rear evaporator corrode over time. This might not seem like such a big deal, but when you take into account that replacement pipes are £1000 PLUS, then you have cost of labour to fit them etc... even if the problem is not a common one, prevention is better than cure.

This also adds to the "underseal" thread, also in this section.

On the E51 isa box underneath the vehicle, at the rear on the passenger side. Inside this box you can see the air con pipes. When you get the car undersealed, ENSURE that whoever is doing the work opens this box and coats the pipes thoroughly with underseal. Also, ensure that the inside and outside of this box are thoroughly coated as well.

The box provides the outer protection for the pipes, so looking after that is one part of the problem. But also coating the pipes will act as a secondary level of security to this issue.

it is not the be all and end all of everything if you lose the air con, but we all know how nice it is on a hot day to whack it on and drive in comfort, after all, why pay for a luxury car that you have to drive sweaty and clammy.

For anyone who has had this issue already, or for any E51 owners that find their aircon does not work. Check this area first. If it's broken, there are two options:

1 - blank off the rear air con. This means you'll still be able to use the aircon up front, but you won't get any cold air through the rear vents. If the system is gassed correctly though, the fronts should be enough to help cool the WHOLE interior down, albeit it will take a little longer.

2 - replace the pipe, which as mentioned above, can cost well over £1000 to repair.

Please see below link to see pictures of the affected area, the pipe that needs replacing, and screenshots of purchase price for replacement parts.

https://flickr.com/photos/9778891@N04/sets/72157659861402231



EDIT: Thanks @Phil for correcting the side the box is on . And thanks @MrRob_in for the images linked, this will be extremely helpful to future members

Great write up and advice. A job for this weekend me thinks

 

[Cainey]

Checked mine and all good, bright and shiny with no corrosion. Will need a small tin of underbody sealer

 

[brent hayes]

Checked mine and all good, bright and shiny with no corrosion. Will need a small tin of underbody sealer

Check behind the greasy sponge foam type material, this is where the moisture collects.

 

[Rayc]

Underbody of the van is mint apart from this...

It was in reasonable good nick considering where its positioned...

but as I'm all for preventive maintenance, I'll get rid of the sponge (as previously mentioned) treat inside & around the pipes with marine grease...& Refurb the cover...

 

[Mark76e]

Underbody of the van is mint apart from this...
View attachment 74583
It was in reasonable good nick considering where its positioned...
View attachment 74584
but as I'm all for preventive maintenance, I'll get rid of the sponge (as previously mentioned) treat inside & around the pipes with marine grease...& Refurb the cover...

Good reminder. I'll do mine this weekend too. I covered mine in waxoyl just before the gritters started last year, having no time to do it properly but I'll do it now