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Allroad C5 4.2 dreaded timing chain failure. Options?

GlennV8ar

New member
So my 4.2 has succumbed to the well known timing chain guide failure common in the allroad 4.2 and S4 4.2 (B6 and B7) which share essentially the same engine, but not in the way you might expect. ItÂ’s an 04 with 205k on the clock, fairly well maintained and minimal mods. It has had the cam chain rattle for quite some time and IÂ’ve been keeping up good oil to it, as per AUDIs recommendation for the fault. I was planning to do the chain guide work to it when it was convenient, but you know how that goes.

My power steering pump started making horrible noises and failed, all very quickly. Seems uncommon, no leaks as reported elsewhere. Extracted the pump, what a pain in the arse as its driven off the rear of the engine by an auxiliary “gearbox” that is chain driven off the crank.

Anyway, pump in hand, it turns smoothly and looks good except for the drive spline and the internally splined shaft that runs into the auxiliary “gearbox” which look abnormally worn and damaged.

back under the car and I can turn the splined drive output with my hand and it feels loose and crunchy:? , IÂ’m assuming that as everything in there is run from the timing and auxiliary chains that something has come away and played havoc.

so now it looks like engine out for repairs to the auxiliary “gearbox” and of course while I’m there, the timing chain guides will be on the menu too.

so thoughts? Do I just source the appropriate parts and repair what IÂ’ve got? Do I try to source a motor that has already had the work done? Do I go for an S4 BBK motor (and 6sp box?)?
 
You would be in line for a lottery ticket to find a recently repaired motor that is now up for sale. Happens I guess but a super long call. As for a motor replacement, it would need to be compatible with all your existing setup electronically or a possible world of pain redoing the loom or modifying ABS and the like. The surest solution is a repair but at some cost so you would really need to accept that it could be half or more than the car is worth. Suitably qualified people have done this themselves and there are some posts on here but not for the faint hearted.
 
Well you never know what’s in the ocean until you throw in a line.

the s4 BBK engine shares everything with the BAS except a few performance enhancers to net an extra 30kw. Dunno if the 6 speed gearbox is physically similar to my 5 speed but willing to do some research.

I’d be doing the work myself, saving a wedge of cash. Owning an old AUDI means knowing how to twirl a spanner. I really do like the car, for better or worse, and I don’t like the idea of sending her off to landfill just for the sake of a minor indiscretion.
 
there are a couple of videos out there from memory showing how and what to do with a timing belt change. From memory, there was one for a B7 RS4...
 
there are a couple of videos out there from memory showing how and what to do with a timing belt change. From memory, there was one for a B7 RS4...

Not to confuse the issue, there is the V8 with the timing belt (RS6 and early V8) and the V8 with the timing chain (B7 RS4 and allroad etc). I have seen something on video about the timing chain but it is a whole different kettle of fish to the belt service.
 
Well you never know what’s in the ocean until you throw in a line.

the s4 BBK engine shares everything with the BAS except a few performance enhancers to net an extra 30kw. Dunno if the 6 speed gearbox is physically similar to my 5 speed but willing to do some research.

I’d be doing the work myself, saving a wedge of cash. Owning an old AUDI means knowing how to twirl a spanner. I really do like the car, for better or worse, and I don’t like the idea of sending her off to landfill just for the sake of a minor indiscretion.

Absolutely, you might improve your chances by including the non RS sources of that base engine. I've never looked at this specific swap so my comments are generic. If you obtained a full B7 RS engine and manual gearbox and ECU and loom you should really only have to check out the existing TCU interfaces to see if anything is dependant on TCU signals.

If you can't get a manual gearbox then you may? have to change cranks to marry up an auto trans if the sourced engine was manual. Lots of transplants are possible with audi gear, it just helps to know all the little things in advance.
 
No rubber band drive here. It’s “lifetime” chains, unfortunately “lifetime“ can be anything from 80k to 300k. Also to clarify, it’s the S4 not the RS4 that shares the most similar engine. As nice as the 300kw+ BNS engine of the RS4 would be, the more humble 254kw BBK and 6speed tiptronic from the B6 and B7 S4 would be more than adequate not to mention actually affordable.
 
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You need to have the engine out first to ascertain what you need. I’ve done a couple. Chain rattle doesn’t always mean broken guides though it isn’t uncommon to have no rattle but still have broken guide/s. The rattle is usually loss of oil pressure in the mechanical cam adjusters due to failed check valves in the valley pan. I would change them first and see if that fixes it. A lot of people (myself included) run an accusump instead of relying on the probe to fail check valves.
If the rattle is still there then you need to pull the engine and trans. There are a few different guides that fail. With it out you then need to check the condition of the locking pins inside the cam adjusters and the solenoids. The chains won’t need replacing.
 
I’m thinking that after 200k I’m inclined to pull the engine/box out and check/replace the lot. Aside from not really knowing the extent of the power steering drive issue, I want to know exactly what’s going on inside.
 
Yep good idea re. pulling the lot. Can give it the once over. Inbox cleared 😎.
 
So engine out and pulled down. Found a broken timing chain guide and the output spline for the power steering pump is stripped out. Rocker cover gaskets are cooked, paint flaking and oil muck under the rocker covers look like ****. valley pan and check valves looks nasty. Inlet manifold flap looks to be seized also.

On a positive note. timing chains, tensioners and other guides look pretty much brand new. I’m hesitant to pull the inlet cam adjusters apart as they’ve not shown any signs of malfunction and re-setting the timing seems to be a pain in the arse.

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That’s good news apart from the pump. I would strongly encourage you to inspect the adjusters as they are a known fail point. I can send you the alignment tools if you need them. It’s way easier than lining up some dodgy marks on timing pulleys etc.
You will notice the difference when you repair the manifold flaps.
 
So the engine has been pulled, tensioners replaced, PS drive repaired and a few little extras while I was there. I’ll update all the details with photos a bit later.

the whole lot is back in, started up beautifully, new fluids everywhere, sounds great.

now the new problem, I have no drive. New ATF, transfer and front diff oils. Dropped the trans sump and replaced the filter, cleaned the sump, all looked good for a 200k+ car.

all fault codes cleared on VCDS.

any ideas on the drive issue?
 
More detail on no drive required.. does it go in gear and rev, but no movement? Does it move a little bit at all?

Sent from my SM-G985F using Tapatalk
 
VCDS is indicating that a gear is selected and trans fluid is heating up. Absolutely no drive or labouring of the engine. Pulling over 1500 rpm brings up an “excessive clutch slip” fault, obviously as it’s getting speed signal in but not out. Also an “incorrect gear ratio “ fault, dunno about that one, I haven’t changed any driveline hardware.
 
Sensor or sensor wire broken at a huge guess.. can you hear the throttle body opening?

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Yeah, throttle is fine. Engine is working normally. I’ve gone over all the connections , cleaned the gearbox ones.
 
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