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Knock knock....knackered AX


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Evening all! The old AX (see thread ‘AX weirdness’ https://autoshite.com/topic/43275-ax-weirdness/ ) has had a bit of a beating up and down from London to the south coast since Christmas - it’s been rock solid though, never missed a beat besides some mystery rich running (solved by switching off the blower motor) and has done a solid 47mpg regardless of how I drive it! 
 

Looking towards summer and some time off, I’m looking at the items that need addressing (frilly boot floor and slightly scabby rear floorpan for starters!) and since December I’ve noticed a very faint (but possibly increasing) knock from the engine. These are tappy old things if the valve clearances aren’t kept up, as you’ll all know, but this sounds lower down, heavier, and a bit big end-ish.

Hopefully I’ll be able to attach a video to this which will show the knock. Happens at relatively low revs - I first noticed it when slowing up to a red light in 2nd gear as the revs fell, but it doesn’t just happen on the overrun, it occurs when the revs are held too. Haven’t noticed it when under load or driving normally and the car is as powerful (relatively speaking!) as it ever was. Hope you can hear it over the valve noise, it’s an odd knocking echo as the revs fall off. Thanks in advance, it’s now pushing 102,000 by the way, poor thing! 
 

Edit - can’t work out how to attach a video, perhaps someone can advise? In the meantime, have a YouTube link! Many thanks all :) 

 

 https://youtu.be/MXYXGACFJ-k

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A judicious oil change and some really good oil initially? I'm not sure of the engine life on these - my diesel has 185,000 on the clock! But the petrols may be a bit more fragile. 

Loads of these breaking in France so when the current Armageddon ends not too difficult to get a motor. 

On the rust... all the AX go there eventually...get up underneath with the jet-wash and  a good wax?

I saw one in the wild this week in London. A rare sighting - was a 1.5D - same colour as mine, same no hubcaps and same giffer in glasses at the wheel as me...🤣😂

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19 hours ago, Faker said:

Light enough knock to be fair. Indirect injection and it could simply be diesel knock 

Seems to be fairly early on, indeed - diesel knock unlikely as it’s a petrol, hard to tell over the valve racket I know! (Unless that’s an expression for petrols which I’ve not come across, in which case I apologise!)

 

19 hours ago, Mally said:

I'm no good with noises because deaf. You need to sell it to someone like me.

Has the oil pressure dropped at all, oil light on at tickover?

Ha! No idea how much it would make on this fine forum, but it’ll be the first place we advertise it when we do need to get rid - working abroad from Summer 2022 and I can’t bear thinking of it being sold, run for a year and then scrapped by a heartless owner for some tiny little MoT failure! 
 

Nope, oil pressure seems good, oil light goes out immediately on startup, compression sounds decent (not got a gauge to check), oil light never comes on round sharp corners or anything like that either. It’s a pretty healthy engine, peppy and with lots (again, relatively speaking) of torque compared to modern 16 valve stuff that I’ve driven. 

 

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23 hours ago, lesapandre said:

A judicious oil change and some really good oil initially? I'm not sure of the engine life on these - my diesel has 185,000 on the clock! But the petrols may be a bit more fragile. 

Loads of these breaking in France so when the current Armageddon ends not too difficult to get a motor. 

On the rust... all the AX go there eventually...get up underneath with the jet-wash and  a good wax?

I saw one in the wild this week in London. A rare sighting - was a 1.5D - same colour as mine, same no hubcaps and same giffer in glasses at the wheel as me...🤣😂

You might be right on some decent oil - probs cheaper and definitely easier than an engine change! Summer and dry weather will herald a thorough scrape down and waxoyl, along with some tickling with a welder around the aforementioned holes.....any idea what sort of price would be fair for such? 

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3 hours ago, AxWomble said:

You might be right on some decent oil - probs cheaper and definitely easier than an engine change! Summer and dry weather will herald a thorough scrape down and waxoyl, along with some tickling with a welder around the aforementioned holes.....any idea what sort of price would be fair for such? 

Difficult one to answer that. Try slowing it by jet washing out the mud traps and cleaning off the worst rust and Vatcan/ waxing the areas. 

If it's not structural/MoT-able I tend to treat  & leave it. 

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  • 5 weeks later...

Thanks @lesapandre, I’ve done the suggested, which should hold off the salt we’ve seen the last month and will protect everything till summer :) knock-off Toolstation vatcan though, hope it does the trick! I think that the boot floor counts under structural/prescribed area sadly, so that will need sorting. As for the floorpans, I think they are less likely to be noticed/failed.

 

@Faker- sadly not a diesel, although it is sounding increasingly ‘knocky’, replacement engine shenanigans coming up! Valve clatter on these old TUs is pretty biblical as you know so close up it does sound like it’s running on heavy oil.... 

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Unfotunately, yes, that sounds like big-end bearings.  Not main bearings, that's more of a rumble, but one of the big ends is probably on its way.  The regularity of the knock and the fact that it's worse when going from off-load to on-load would suggest.

.. and yes, your tappets are quite tappety.

I'd have the sump off (dead easy on these) and then heave at each of the rods in turn.  you may be able to move one by a fair bit more than you should.  Big ends are changeable fairly easily, so as long as it's not wiped out the crank journal, it's an easy enough fix

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PSA TU engines should be relatively long lived if looked after; 200k isn’t unusual for a well looked after one. Through experience of working on plenty of French cars the tappets should tick sweetly not sound like a sack of spanners. Regular, rhythmic knocking which matches engine revs is almost certainly big ends.
 

Does the knocking get quieter/go away as the engine warms up? (I have known TUs get piston slap)

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On 4/23/2021 at 12:45 PM, Talbot said:

Unfotunately, yes, that sounds like big-end bearings.  Not main bearings, that's more of a rumble, but one of the big ends is probably on its way.  The regularity of the knock and the fact that it's worse when going from off-load to on-load would suggest.

.. and yes, your tappets are quite tappety.

I'd have the sump off (dead easy on these) and then heave at each of the rods in turn.  you may be able to move one by a fair bit more than you should.  Big ends are changeable fairly easily, so as long as it's not wiped out the crank journal, it's an easy enough fix

It’s definitely something to do before we swap the engine out, but sadly it’s an oil burning nightmare at MoT time (well, it burns oil all the time but it’s more of an issue during the test) , valve stem seals are shot, pretty sure the rings are done for as well so a low mileage donor is a better option on many points. Feels a bit like defeat but I’m not sure it’s fit enough to justify a rebuilt when so much would be involved. Plus I have a mate with a recently installed lift! 
 

On 4/26/2021 at 9:39 PM, dozeydustman said:

PSA TU engines should be relatively long lived if looked after; 200k isn’t unusual for a well looked after one. Through experience of working on plenty of French cars the tappets should tick sweetly not sound like a sack of spanners. Regular, rhythmic knocking which matches engine revs is almost certainly big ends.
 

Does the knocking get quieter/go away as the engine warms up? (I have known TUs get piston slap)

I’ve read such good things about them, but I think this one has been abused, judging by some of the bodges I’ve found and the accelerated engine wear I’m experiencing. It matches the engine revs, rises and falls with the revs but actually gets slightly worse as the engine warms up. It used to not do it till it was warm, now it does it all the time but is quieter on startup and gets louder after a few mins. Mentioning piston slap, that is another reason for replacement, aside from the aforementioned knock, there’s also a violent rattle that’s apparent one particular point (same point every time) when pulling away in 1st, regardless of how you treat the clutch and throttle, that sounds exactly like our old Seicento which was condemned for knackered rings.  Sounds like a screwdriver being rattled around in a beans tin, but it’s done that since 93,000 miles! No mystery where all the oil is going....

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20 hours ago, AxWomble said:

I’ve read such good things about them, but I think this one has been abused, judging by some of the bodges I’ve found and the accelerated engine wear I’m experiencing. It matches the engine revs, rises and falls with the revs but actually gets slightly worse as the engine warms up. It used to not do it till it was warm, now it does it all the time but is quieter on startup and gets louder after a few mins. Mentioning piston slap, that is another reason for replacement, aside from the aforementioned knock, there’s also a violent rattle that’s apparent one particular point (same point every time) when pulling away in 1st, regardless of how you treat the clutch and throttle, that sounds exactly like our old Seicento which was condemned for knackered rings.  Sounds like a screwdriver being rattled around in a beans tin, but it’s done that since 93,000 miles! No mystery where all the oil is going....

Yes that definitely sounds like ends. Piston slap has a tendency to ease off as things warm up. You could put a thicker oil in it (20w50), it's a bit of a bodge to give you a little more life but it's not always great for other parts of the engine. An exchange or good second hand unit shouldn't be too expensive but as Talbot says it's not too difficult to change the big ends in these. If you need liners and pistons as well you will be hitting several hundred quid, but I think it's worth it as AXs aren't commonplace now, and you obviously enjoy the car.

You may also have a gearbox or clutch issue when you pull away from standstill. Try pulling away in second (downhill) and see if the rattle is still there.

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