Coolant leak from rear flange: Sourcing the coolant pipe?

[defever]

Hello (again...) B5 drivers,

I found a coolant leak (trickle for now so not really urgent) at the back of the engine:

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It's the pipe at the rear flange (35):
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The part code for the flange is either 028121145E (flange; for vehicles with glow plug; heater) or J (flange with quick act.coupling; for vehicles with glow plug; heater), not sure which one I have or what the difference is.

I think the flange is okay, and it seems to be leaking from the pipe. A garage replaced the clamp (N10258101, 23-35X9X0,5) couple of month ago but the leak hasn't stopped.

So, I want to replace the pipe to see if that makes any difference. But there's no part code on the catalogue (only says "see illustration:; 819-50"). I can't really see where the other end of the pipe is connected to, but I'm assuming that it's coming from the cabin air vent circulation? It disappears under the windscreen scuttle.

Does anyone know how to find the part number for the pipe or source the pipe, please?

Thanks very much for your help.

PS. The more I look into the engine bay, the more task I find... I'm having fun playing with my car, for sure.

[Nigella]

Thats the HOT feed hose that goes on up to the Heater Matrix... (It goes from the back of the head where the glow plug 'flange' heats the water up prior to going through the under tray close to the battery securing bracket, by the bulkhead and on to the heater matrix)



These do burst under pressure, as mine did last year but I was able to cut the holed section out, lengthen the hose by moving the heater matrix end closer to the end of the feed pipe which gave me an extra 1.5" to play with.



I don't know the part number sorry. If I find it I will post it as I am looking to replace all of my hoses. I believe there are dealer only parts... :(




PS Mine is the same car of 1998 vintage with 302,000 miles!

[defever]

Thanks very much Nigella,

It's really good to know where the turbe is connected to. The car is off to a garage for this and other things so hopefully they can replace the tube all together.

On a similar note, I'm wondering if replacing all rubber / braided tubes and hoses on the car to a scilicone alternative is needed at some point in its life as a high mileage car!

Thanks very much once again!

[defever]

Just a little update on this, if anyone is having a similar issue.

I took it to a garage last week and had the pipe cleaned and new clip installed. It is still dripping and after a long distance you can notice some pink fluid stain below the pipe (on the transimission caging).

The garage is thinking, as next solution, to replace the pipe and the flange with the glow plugs (and the plugs, might as well, while they are going to work on it...). I think the flange is around £45 and maybe £5-10 each for the plugs? They didn't have the price at hand for the pipe.

As they cleaned the pipe and the leak is still present, I agreed to replace the flange as well with a new pipe just to make sure, but a part of me is doubting is it necesary?

I will report back later this week when it goes back to the garage.

[Nigella]

I replaced the vacuum hoses with silicone ones a year ago. They looked good and for a few months and they did the job quite well...

About four months in, I started to have problems with the turbo not spooling up and giving the boost required, having intermittent boost spikes and boost failures. On inspecting the silicone hoses when hot, I found that they would collapse under vacuum and had in fact fractured in a few different places where they joined the hard plastic pipes allowing leaks.

I'd steer well clear of silicone hoses unless they are made especially for the Audi...

The other downside to silicone I found is that they can collapse when warm and your vacuum efficiency dies off quite dramatically. I have now gone back to the original braided hoses as fitted from new and all is fine.



I would suggest that silicone is fine for some applications, but as for the vacuum hoses, I would stick to the originals.


N.

[defever]

Thanks Nigella for the silicone feedback. When I replaced mine, I replaced it with 3mm inner diameter silicone hose. Some OEM braided hoses are much thicker than this (e.g. the one that connects to the top of the air box). It was tricky to fit little 3mm tube on to larger diameter nipples and fitting with brutal force will definitely rip the silicone easily. So I can see them fail in these points. However, I tested the vacuum through the silicone hose from N18 when I removed EGR and the suction is strong enough. So, as long as you have the correct silicone tube with the right diameter for each route, I think it'll hold. My original braided hoses were wearing off so at least the new silicone will do a better job than that. So I tell myself.

[defever]

Update on the coolant leak.

Got the car back from the garage (after two visits for other jobs on oil leak and steering noise), they cleaned the pipe and "sealed" it and told me to keep checking for leaks. Well it's still leaking, and they also knew that. They said it leaks less. I said it still leaks. So, they quoted £200 for pipe, flange and labour (excluding the three glow plugs, if they need replacing). In all fairness, they didn't "charge" me for this particular job this time around (as it has been looked in January, just replaced the jubilee). But I cannot hide the feeling of bit fobbed off; I'm sure there's some misunderstanding. Maybe they think I’m a chav driving an old incontinent car and not worth their time…

So I've seen the diagram, I vaguely know where the pipe goes to (though I don't have the part number yet), I might do this myself.

Pipe, flange, 3x glow plugs. Anything I should be aware of for this task? As it sits at the top and back of the engine block, is complete flushing of coolant necessary or can I get away with draining from the flange and top up from the reservoir when I replace the parts?

[Rob69]

I think your problem is the hose internal wall is split inside around the bulge where it goes over the 'pipe' and fluid is migrating down the internal brading to come out and drip. I doubt it is the pipe that is at fault, short of it being cracked I can't see how it would leak other than from the flange joint, and your's is from the hose to pipe joint. Only solution I can see is new hose or if you have sufficient slack in the hose, cut the end off and re secure to the pipe but it looks tight for that.

[defever]

Okay, managed to find the diagram for the pipes!

AUDI A4/AVANT [A4] (EUROPE) 1999 [ >> 8D-X-199 999]: BODY: 81950. HEAT EXCHANGER; COOLANT HOSES (http://www.partsbase.org/audi/audi-a4-avant-a4-eu-1999-8d-x-199-999-81950-heat-exchanger-coolant-hoses/)

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It must be either #2/A or #3/A.

#2/A is "coolant hose; (heat exchanger>coolant p.); return; rhd" (8D0819373M (http://www.partsbase.org/parts/aud-8d0819373m/))
#3/A is "coolant hose; (flange > heat exchanger); feed; rhd; ADP,AHU,AFN,; AFF,AHL,AHH" (8D0819371N (http://www.partsbase.org/parts/aud-8d0819371n/) or 8D0819371AC (http://www.partsbase.org/parts/aud-8d0819371ac/))

I'm presuming it's #3 that I need, but there are two part variations ("N" or "AC") for RHD AFN engine.

Does anyone happen to know the exact part number, or if there's any difference in those two?

[defever]

Thanks very much Rob69,

I unintentionally used the words "hose" and "pipe" interchangeably to describe the rubber tubing. I can see your explanation and I am convinsed that it's the rubber hose at fault and not the metal flange. I doubt the metal flange can crack even at pressure. If it was a plastic flange, yes, I might suspect it, but not if it's a metal flange.

I'm tempted to cut the end of the hose, as you say and shimmy a bit to see if it's the cause, but if it's necessary to flush the coolant and bleed to do the job (is this necessary or can I just pull the hose and top up after?), then I feel I should just replace the hose all together.

I will do some more homework to find the correct replacement part and I'm pretty sure I will end up doing this myself.

Hopefully it'll be a simple removal and replacement of the tube.

[green A8]

One little tip I recently gleaned from this very forum that might help you, and others, is that you can drain down the coolant from the oil cooler. Thus saving the bother of removing all the coolant. I simply replaced the pipes back onto the oil cooler once the required coolant had been drained off. It saved faffing around with the rad hoses, which can be a pain sometimes.

I can't see why replacing the offending hose and or flange and heater glow plugs wouldn't be a fairly straightforward DIY job. But if you get stuck you can always seek advice from this very place. I have to say, I'd be tempted to renew both of the heater matrix hoses whilst I was at it. Take care when you remove them from the matrix end as the plastic nipple/connection at that end has been known to split/snap or crack. Brute force is not needed. If they do break a new matrix will be required, a blooming nightmare on a B5. A dashboard out job I'm afraid.

[Nigella]

Where in Sussex are you? I am working in Kent for a few weeks and come into Winchelsea, Northiam and Rye quite regularly... It might be I can give you a hand to do the job if you wish? I will PM you some contact details and see if I can help from there...


I also get a good discount rate from the local motor factors so might be able to save you a few quid as well.



I cut the hose on mine and have only just had a leak re occur but its only a weep... I would try and get it fixed yourself as £200 for the hose is ridiculous! Its also only a 5 minute job including bleeding the system afterwards...


N.

[Rob69]

Hows about this to avoid draining the coolant: remove the jubilee clip by completely unscrewing it, with a sharp stanley or craft knife slice right round the hose where the jubilee clip was, slice the end bit of hose lengthways and remove that bit.
shimmy the hose further up, repeat if necessary then replace the jubilee clip. Sure you get the idea.

[Nigella]

Hows about this to avoid draining the coolant: remove the jubilee clip by completely unscrewing it, with a sharp stanley or craft knife slice right round the hose where the jubilee clip was, slice the end bit of hose lengthways and remove that bit.
shimmy the hose further up, repeat if necessary then replace the jubilee clip. Sure you get the idea.


This wont work in this case as you need to cut the bulging section out of the hose, thats where it is leaking from, also cutting into the aluminium will leave a groove which can cause leaks when under pressure.

Stick with the basics and do the job properly first time round. Bleeding the system is simplicity itself on this car.

N.

[defever]

Good morning and thanks everyone for your advice!

Great tip from green A8, thanks very much about the oil cooler advice. It just on top of the oil filter and I think I can access it quite easily. I’m thinking of catching the coolant in a pan so that I can reuse it (it’s just been replaced last week when the garage too the faulty hose and “cleaned” it); as long as it pours out clean. If it doesn’t look like I can drain cleanly from the oil cooler, then I’ll just drain the whole fluid from the bottom of the radiator and do the proper flush & bleed.

As to Rob69’s advice on cutting up the hose in situ, yes I also had this idea, but not really knowing how or where the point of leak is, and the risk of scraping the flange pipe, I thought it’s probably best to remove and replace with new hose as Nigella suggested. Thank you both, it’s very reassuring that my train of thought is in the right path!
I’m a bit unsettled with the garage about this whole thing; they are very reputable in the area and I know quite a lot of people who use and praise them. I’ve used them for the last two years but as I learn more about my car, I’m beginning to see the little details that they seem to miss.

Having to just replace the jubilee in Jan (told me to watch for further leak, which it did), then to remove and just “clean” the hose two weeks ago (again told me to watch for further leak, and it has by the time I collected the car), and then to quote me £200 for new hose, flange and labour (+glow plugs if needed replacing) last week doesn’t quite cut it. Why haven’t they replaced the hose if they removed it and “cleaned” it? It looks like a simple job but they seem to either do the minimal or suggest an overkill to replace both hose and the flange. I will kindly ask for some clarity and I’m hoping that it’s my misunderstanding, but I couldn’t help wonder.

I’ll get both of the hoses ordered and see if I can tackle it this week or next. I will be very careful with coolant gushing out everywhere and the matrix pipes (I’m quite sure it’s very fragile).

Thanks everyone once again!

[defever]

Good morning,

Here's another update on this. Thanks to Nigella's help, I've ordered some parts to replace in hope to rectify the leak! I had a good look under the bonnet to see how I can get around this and I feel quite comfortable that I can do this. Rather than just replacing the hose at fault, I decided to replace the other coolant hoses that are unlikely to be replaced since manufactured.

So I ordered these:

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#35 Coolant hose (flange > heat exchanger) rhd AFN: 8D0 819 371 AR (says N or AC online but AR is the updated code) - £24.98
#35 Coolant hose (heat exchanger > coolant pump) rhd: 8D0 819 373 M - £19.60

#3 Coolant hose (oil cooler > water pipe) return: 058 121 058 B - £14.88
#4 Coolant hose (coolant pump / pipe) return: 048 121 063 - £9.05
#1 Coolant hose (flange > oil cooler > coolant pump) AFN: 028 121 053 AA - £38.16

#10 Coolant hose (expansion tank >; flange > coolant radiator): 8D0 121 101 AJ - £52.30
#2 Coolant hose (expansion tank > coolant; radiator > coolant pump) return: 8D0 121 055 F - £49.07

And if anyone is wondering how much the oil cooler and the glow plug at the cooler flange are...

Oil cooler AFN: 028 117 021 E - £132.73
Oil cooler hex nut: 068 115 723 - £1.20
Glow plug (for vehicles with glow plug heater; M12X1,25X21; AFN) - approx. £9.00

Price is excluding VAT and at "trade" rate... that's a grand total of over £410.00 including VAT!

I only opted in for the first five hoses + glow plugs (approx. £160.00), as the top & bottom radiator hoses and oil cooler didn't look too bad (and they are the most expensive parts on the list!). I've read around enough to understand that oil cooler needs to be inspected if there's oil in the expansion tank or excessive bubbles on the dip stick. I don't have either for the moment so they can wait a while.

It might be a slight overkill (I might not need glow plugs) but it'll give me some piece of mind that those hoses will be new and won't leak in near future (hopefully).

[Doctle Odd]

There's a drainage bung on the radiator so it's easy to catch the coolant. I have worked on plenty of these cars, on most of them the coolnt heater plugs were dead and TBH replacing them makes very little difference unless you live in a very cold climate I think they just put a little extra drain on the battery. That's just my 2/-

[defever]

Perfect, thanks very much, as always, Doctle!

I hardly touch the heater all year round, only to de-mist windscreen on cold days (cold meaning - 2 ~ +5C on south coast...). I had a feeling glow plug isn't necessary so I won't pick them up (it'll save me £30+). I even thought of changing the flange to non-glow plug flange (028121144N or 028121145C, both for automatics and looks like there's a plug for some sort of sensor) but I haven't quite go there yet to check if it's compatible.

I learned how to flush from the bottom of the radiator and bleed properly (by elevating the expansion tank) when replaced the thermostat so I'm familiar with how to get the fluid out. The fluid has only been replaced couple of weeks ago by the garage so I'm hoping to drain it cleanly and reuse most of it.

Coolant system is an expensive job!

[Doctle Odd]

There's a bleed hole in one of the metal pipes at the bulkhead you just pull the rubber pipe back to uncover the hole. Most of those flanges have the holes same distance apart so it isn't too difficult to get one that will fir. I think the price quoted for the oil cooler is a little steep!

[defever]

Here's the said bleeding hole on the "heat exchanger > coolant pump" hose:

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And it looks like the leaking hose has been shimmied a bit, too.

The prices I noted are Genuine VAG parts from TPS at "trade rate"... They are steep and I can see "high quality" coolers for £65 on eBay... I remember paying nearly £35 for the thermostat at the same place but seeing £5-7 thermostats elsewhere... I kept telling myself that the one I bought is genuine and MUCH better than the cheaper equivalent...

[Doctle Odd]

One of those pipes has the bleeding hole. Cheapo thermostats and CTS are useless

[defever]

UPDATE

I GOT THE WRONG PARTS!!:

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I was told over the phone that the part number with "AR" at the end was the revised part number for 8D0 819 371 N and C... the AR part has the flange end in plastic with clip, just like the other hose from the heater matrix.

I only realised this when I already flushed from the radiator and removed the two hoses from the heater matrix... so I carried on by cutting the end of the old hose and fitted back in... Bled the system by elevating the expansion tank and blowing "HI" on heater and pumping the top radiator hose. Heater blowing scorching hot air, fluid level is stable after 90C, no leak so far so it's temporarily put back in for now.

The plastic pipe from the heater matrix looked pretty pristine so I was happy about that. But oh my word, what's up with the double grommet on the heater matrix hoses! It was such a nightmare to get the hoses out and back in. I wanted to check couple of things about this grommet:



Can I discard this grommet like the other drain grommet that's notoriously well known for clogging up and flooding the footwell?
I noticed that the clear tube feeding from the battery also goes through this. I only noticed this after I fiddled around with it in anger. Should the battery hose be connected to something else on the other side, through the firewall?


Otherwise, a semi-finished repair done today... hmm.

[defever]

Following up on the two questions, I figured the hose from the battery is just a vent so it doesn't need to be plugged in to something on the other end, so it should be just hanging down past the bulkhead.

I searched for removing the heater hose double grommet, but there’s no reference for removal nor keeping it. All the web pages I found are about the drain plugs under the brake servo and battery (the ones that causes block and floods the footwell). So I think I’ll keep the grommet and place it properly with the battery out for more space.

Left the car overnight and there’s no leak around the flange whatsoever, and nothing under the car this morning so I had a great sense of relief that I finally won the battle of leaky coolant. I’m returning to TPS with the wrong hose, and will order the correct hose to replace soon. But in the meantime, the coolant is sealed. I replaced couple more hoses that I could easily access (the other heater hose and one of the short hoses going into the oil coolant); there were some crystalised pink residue on the pipe so I’m glad I replaced them for precaution. Other ones were too deep down by the engine (and looks like the fuel filter needs to come off for access) so I stopped there.

Thanks very much everyone for helping me out on this!

[defever]

Duplicate message removed...

[defever]

Little update on this.

After 1,000miles, there hasn't been a drop of coolant leaking anywhere! I haven't had the chance to replace the cut hose but I'm happy for it now so I can wait.

I did the usual oil change the other day so while I was waiting for the oil to drain, I took out the battery and re-fitted the double grommet attached to the two heater hoses. The condenser metal pipes were in the way so it was hard to manoeuvre but I got there in the end.

All in all, a success!