I have just aquired a zx diesel which sounds worse than some of the old french tractors that pass my house.It starts perfectly and does not smoke.All four cylinders are functioning o.k.{slackened injectors on each cylinder with noticible effect.
Can anyone please inform me if the 1994 zx diesel{non turbo}is fitted with hydraulic tappets.
I have checked clearences and some seem to be only a thou or two whilst others read 12 thou plus.
Have I got knackered lifters which are causing lack of power and such a racket??
Any tips on installing replacements{if required}appreciated.
p.s engine done 140k.
Help greatly appreciated as the froggie garages tend to rip off the brits somewhat and I would love to fix this myself and preserve my eardrums a while longer!
ZX diesel,Hydraulic tappets???
Moderator: RichardW
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terryinfrance
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Dave Burns
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terryinfrance
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thanks for reply Dave,whats going on?thats a good question!Are you saying the clearances are achieved by shims?
Can you advise me of inlet/exhaust clearances cold/hot?
I cannot explain the variations,the car has been driven by a friend of mine with no known recent mechanical work.
As mentioned previously the engine is very noisy/clattery and seems to lack power.On checking valve clearances I found this variation.
There is no smoke and starting is good.
Terry
Can you advise me of inlet/exhaust clearances cold/hot?
I cannot explain the variations,the car has been driven by a friend of mine with no known recent mechanical work.
As mentioned previously the engine is very noisy/clattery and seems to lack power.On checking valve clearances I found this variation.
There is no smoke and starting is good.
Terry
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Dave Burns
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If the clearances are that tight it sounds as though the valves could be/have been burning into the valve seats. This would be unusual on these engines, but its unlikely that someone has adjusted the clearance to this.
Regarding the noise, have you checked the tension of the timing belt? Has the car any service history because without it the motor may not be in particularly good condition. What does the camshaft itself look like, is it in good condition.
Does it start instantly from cold after glow plugs go off? It should do. Once it has been run for a few minutes it should start more or less instantly on the key without the need for glow plugs.
Check these and report back.
Regarding the noise, have you checked the tension of the timing belt? Has the car any service history because without it the motor may not be in particularly good condition. What does the camshaft itself look like, is it in good condition.
Does it start instantly from cold after glow plugs go off? It should do. Once it has been run for a few minutes it should start more or less instantly on the key without the need for glow plugs.
Check these and report back.
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terryinfrance
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Thanks Dave for info.if injection was too far advanced what smoking symptoms would I get?
Jonesy-No 1.burnt valves?exhausts were o.k at 12thou,a couple of the inlets were down to 2 thou,too tight,but will this cause noise?
no 2.belt not checked yet[not a timing belt type noise though]will checkall the same.
no 3.no history,poss poor motor,but no smoke at all,starts superb from cold,as yet to check re start after running/hot.
Are you hinting at piston slap?if worn would I not have smoke and heavy breathing thro oil filler etc.{not breathing too bad for 140k]
Bottom end sounds o.k.
Thanks guys.
Jonesy-No 1.burnt valves?exhausts were o.k at 12thou,a couple of the inlets were down to 2 thou,too tight,but will this cause noise?
no 2.belt not checked yet[not a timing belt type noise though]will checkall the same.
no 3.no history,poss poor motor,but no smoke at all,starts superb from cold,as yet to check re start after running/hot.
Are you hinting at piston slap?if worn would I not have smoke and heavy breathing thro oil filler etc.{not breathing too bad for 140k]
Bottom end sounds o.k.
Thanks guys.
Unless you know the history of the car and know the cambelt has been changed within the recommended time you should have it changed immediately as they can break and will do substantial damage.
To adjust the valve clearances you will have to remove the camshaft and change the shim under the cam follower for the correct value. As you are dismounting the camshaft pulley its probabaly a good time to change the cambelt.
Were all the camlobes in good condition? A small amount of wear (usually indicated by a surface that looks like concrete) can cause a change in profile and noise.
Are you sure all the ancilliaries are running quietly? Alternators can make loads of noise as probably can water pumps and power steering pumps when on their way out. Remember there is also a pulley on the cam belt drive. The drive belts themselves can be noisy - I had a Renault 21 and the only way I could get that quiet was to smother the belt with vaseline.
I agree that piston slap would seem unlikely with good starting. I would expect it to disappear as the engine warmed up and the pistons expanded.
Another source of noise could be the exhaust - leaks at the manifold or pipe/manifold joint.
The reason for the small inlet valve clearances is probably sinkage of the inlet valve seats - a problem I thought was confined to 1.7's for some reason.
jeremy
To adjust the valve clearances you will have to remove the camshaft and change the shim under the cam follower for the correct value. As you are dismounting the camshaft pulley its probabaly a good time to change the cambelt.
Were all the camlobes in good condition? A small amount of wear (usually indicated by a surface that looks like concrete) can cause a change in profile and noise.
Are you sure all the ancilliaries are running quietly? Alternators can make loads of noise as probably can water pumps and power steering pumps when on their way out. Remember there is also a pulley on the cam belt drive. The drive belts themselves can be noisy - I had a Renault 21 and the only way I could get that quiet was to smother the belt with vaseline.
I agree that piston slap would seem unlikely with good starting. I would expect it to disappear as the engine warmed up and the pistons expanded.
Another source of noise could be the exhaust - leaks at the manifold or pipe/manifold joint.
The reason for the small inlet valve clearances is probably sinkage of the inlet valve seats - a problem I thought was confined to 1.7's for some reason.
jeremy
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Dave Burns
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Moderate increases in injection timing typically don't increase black smoke in the low to mid speed range and can even reduce smoke, at high engine speeds though black smoke will increase with over advanced injection timing.
At lower speeds the point of injection is still relatively close to optimum temperature generation combined with the time it takes to burn the fuel and the amount of fuel to be burned, much to far advanced as during high engine speed sees injection take place before optimum temp causing lower vapourisation of the fuel, so it burns from a more globular state, this along with the fact that at higher speeds there is less burn time and more fuel to be burned results in partial combustion giving rise to black smoke.
Dave
At lower speeds the point of injection is still relatively close to optimum temperature generation combined with the time it takes to burn the fuel and the amount of fuel to be burned, much to far advanced as during high engine speed sees injection take place before optimum temp causing lower vapourisation of the fuel, so it burns from a more globular state, this along with the fact that at higher speeds there is less burn time and more fuel to be burned results in partial combustion giving rise to black smoke.
Dave
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terryinfrance
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Thanks guys for all the info.I am in the process of investigating further.
I have experienced noisy belts/pumps before and although this is all relavent re. noises and the inherent difficulty in describing them I am inclined to think fault lies with valvegear or possibly a worst case scenario of little ends.These do normally make[in my experience a more rythmic note.
Its belting down with rain at the mo here in Brittany,but I will have a further look a.s.a.p and hopefully come up with some sort of diagnosis.
It is fair to mention that when I hold my ear on the plenum/air box the racket seems to be very valvey/tappety but it is so much harder to pinpoint with all the other diesel type noise.
To recap,on originally checking clearances the exhausts seem to be o.k at 12 thou,a couple of the inlets were barely 2 thou although I could spin the buckets so they are free for sure.The thing is would a couple of albeit tight clearances give cause to such a racket.
It has all the classic sound of piston slap with none of the other givaways of a knacked engine.
It is undoubtedly true the engine has suffered from lack of maintenance in the past although on checking oil feed to valvegear this was quite satisfactory with all lobes good and no scoring/surface deterioration visible.
Further investigation imminent,but any further suggestions welcome
I have experienced noisy belts/pumps before and although this is all relavent re. noises and the inherent difficulty in describing them I am inclined to think fault lies with valvegear or possibly a worst case scenario of little ends.These do normally make[in my experience a more rythmic note.
Its belting down with rain at the mo here in Brittany,but I will have a further look a.s.a.p and hopefully come up with some sort of diagnosis.
It is fair to mention that when I hold my ear on the plenum/air box the racket seems to be very valvey/tappety but it is so much harder to pinpoint with all the other diesel type noise.
To recap,on originally checking clearances the exhausts seem to be o.k at 12 thou,a couple of the inlets were barely 2 thou although I could spin the buckets so they are free for sure.The thing is would a couple of albeit tight clearances give cause to such a racket.
It has all the classic sound of piston slap with none of the other givaways of a knacked engine.
It is undoubtedly true the engine has suffered from lack of maintenance in the past although on checking oil feed to valvegear this was quite satisfactory with all lobes good and no scoring/surface deterioration visible.
Further investigation imminent,but any further suggestions welcome
Terry -
My present running '89 BX16 (carburetted) suffers from piston slap - with the wellknown "pockety-pockety-pockety" sound when running on light load (cruising at low speed).
When aquired - this car had fitted a "Purolator" engine oil cleaning system - which employed a take off hose fitted into to sump drain hole - running to a can with a re-usable filter & either a pump or heater element - and back to the oil pressure switch hole - fitted with a T-piece for the pressure switch.
On checking the oil with car home 1. day - it was hair-raising - the oil resembled black ink - with the fingers test.
First job then was removing the "oil-cleaner" and replacing the oil & filter. BTW the old filter can had a rust pinhole - seeping out engine oil [:0] - telltale !
Now the engine is running with synthetic 5w40 oil (replaced 2x now) - the oil now looking allmost clean - and the engine running surprisingly well - no oil consumption.
I suspect that it's the liners that have suffered badly from the in-adequate lubrication - thus allowing the pistons to slap around. I'm just preparing for a "miracle-cure" - knowing from ancient badly worn engines I had - that works :
Adding a tephlone based additive to the oil. It does of course not cure the problem itself - but the slack will be minimised - and so the noise.
Happily I have a couple of spare engines in the yard - which on testing shows as promising spares [:p]
My present running '89 BX16 (carburetted) suffers from piston slap - with the wellknown "pockety-pockety-pockety" sound when running on light load (cruising at low speed).
When aquired - this car had fitted a "Purolator" engine oil cleaning system - which employed a take off hose fitted into to sump drain hole - running to a can with a re-usable filter & either a pump or heater element - and back to the oil pressure switch hole - fitted with a T-piece for the pressure switch.
On checking the oil with car home 1. day - it was hair-raising - the oil resembled black ink - with the fingers test.
First job then was removing the "oil-cleaner" and replacing the oil & filter. BTW the old filter can had a rust pinhole - seeping out engine oil [:0] - telltale !
Now the engine is running with synthetic 5w40 oil (replaced 2x now) - the oil now looking allmost clean - and the engine running surprisingly well - no oil consumption.
I suspect that it's the liners that have suffered badly from the in-adequate lubrication - thus allowing the pistons to slap around. I'm just preparing for a "miracle-cure" - knowing from ancient badly worn engines I had - that works :
Adding a tephlone based additive to the oil. It does of course not cure the problem itself - but the slack will be minimised - and so the noise.
Happily I have a couple of spare engines in the yard - which on testing shows as promising spares [:p]
Terry
The one question I've avoided answering is 'will the reduced tappet clearance produce noise' and when I think about it the answer is possibly yes. The cams have silencing curves which are designed to produce a gentle acceleration of the valve and tappet and so enable it to stick to the cam profile and function quietly and without bounce at high revs. Thinking back to ancient engines without silencing curves their clearances were typically 3 or 4 thousandths of an inch which I think equates to 0.076 to 0.10 mm. Such engines often sounded a bit busy even at those clearances. What may be happening is that there is contact between the tappet and the cam off the curve and this causes a sharp knock.
As the engine warms up the clearances will increase as the alloy head expands and the valve may well quieten a bit as the silencing curve comes into play.
I know that these curves are very effective but also sensitive to wear from experience of trying to adjust out wear on engines with worn cam followers, the only satisfactory answer being replacement.
jeremy
The one question I've avoided answering is 'will the reduced tappet clearance produce noise' and when I think about it the answer is possibly yes. The cams have silencing curves which are designed to produce a gentle acceleration of the valve and tappet and so enable it to stick to the cam profile and function quietly and without bounce at high revs. Thinking back to ancient engines without silencing curves their clearances were typically 3 or 4 thousandths of an inch which I think equates to 0.076 to 0.10 mm. Such engines often sounded a bit busy even at those clearances. What may be happening is that there is contact between the tappet and the cam off the curve and this causes a sharp knock.
As the engine warms up the clearances will increase as the alloy head expands and the valve may well quieten a bit as the silencing curve comes into play.
I know that these curves are very effective but also sensitive to wear from experience of trying to adjust out wear on engines with worn cam followers, the only satisfactory answer being replacement.
jeremy
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terryinfrance
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Thanks again guys for all your advice.Firstly I must retract my original remark re. french garages.because,today I visited my local small town renault garage for an opinion.
He suggested having a look and re-checked valve clearances with following result no.1 inl.0thou exh 12thou. no 2. inl.2thou. exh.12thou. no 3. inl. 0thou. exh. 12 thou. no 4. inl 4thou. exh 12thou.
{it appears two inlets have burnt/pocketed. all exhausts are to spec.
He performed a compression check and found no.1. and no.4 cyls. poor compression.He made a comment re. poss deterioration of pre combustion chambers[a new experience for me previously only being a petrolhead!!]
All this was FREE OF CHARGE!!!
He suggested the engine was DONALD DUCKED and I should seek a replacement used unit.
So the dilema is this.I have low compression on two cylinders with minimal clearance on at least two inlet valves.
Opinions please on whether you think its the poor combustion on poss 2 cylinders caused by lack of compression that is causing noise.
A pal has suggested removing head first before going the replacement engine route.On removal checking piston movement at t.d.c
Opinions greatly appreciated.
Terry
He suggested having a look and re-checked valve clearances with following result no.1 inl.0thou exh 12thou. no 2. inl.2thou. exh.12thou. no 3. inl. 0thou. exh. 12 thou. no 4. inl 4thou. exh 12thou.
{it appears two inlets have burnt/pocketed. all exhausts are to spec.
He performed a compression check and found no.1. and no.4 cyls. poor compression.He made a comment re. poss deterioration of pre combustion chambers[a new experience for me previously only being a petrolhead!!]
All this was FREE OF CHARGE!!!
He suggested the engine was DONALD DUCKED and I should seek a replacement used unit.
So the dilema is this.I have low compression on two cylinders with minimal clearance on at least two inlet valves.
Opinions please on whether you think its the poor combustion on poss 2 cylinders caused by lack of compression that is causing noise.
A pal has suggested removing head first before going the replacement engine route.On removal checking piston movement at t.d.c
Opinions greatly appreciated.
Terry
Terry -
My option would be :
Remove cylinder head & inspect for any serious damages. Small cracks around the pre-combustion chambers are normal - but if severe - the head is DONALD DUCK.
If no severe damages - an overhaul of the head may be considered.
Even considered the relatively high cost of a replacement head - this may proove the cheapest option - since replacing the engine may end up with a higher bill - considering the labour work - and once again you have bought a lotteri note.
My option would be :
Remove cylinder head & inspect for any serious damages. Small cracks around the pre-combustion chambers are normal - but if severe - the head is DONALD DUCK.
If no severe damages - an overhaul of the head may be considered.
Even considered the relatively high cost of a replacement head - this may proove the cheapest option - since replacing the engine may end up with a higher bill - considering the labour work - and once again you have bought a lotteri note.
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Dave Burns
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I find those valve clearances somewhat strange, all the exhaust clearances are bang on spec. and yet the intakes are all over the shop, if any valves are going to be badly burnt its allways the exhausts that come off worst in my experience, after all they are the ones opening and closing under the worst conditions, that being hot burning gasses.
The intakes are opening and closing in clean cool air for the most part, on top of that the intake heads are larger in diameter and so should wear slower than the exhausts for that reason alone, in my book at any rate.
I can't accept that the exhausts have not budged one iota out of spec. in all that mileage and yet the intakes have gone daft, 0,2,3 and 4 thou doesn't sound very consistent either given that they have all gone through the same engine cycles I would have expected better consistency, not the sort of thing I've come accross on engines that I've had to bits.
If you take the head off don't be too alarmed at lateral piston movement when cold, they will move.
Check for a lip at the tops of the bores, if you drag a finger nail up them and it snags on a pronounced lip then thats not good, there should be hardly any, don't mistake it for carbon buildup though.
Dave
The intakes are opening and closing in clean cool air for the most part, on top of that the intake heads are larger in diameter and so should wear slower than the exhausts for that reason alone, in my book at any rate.
I can't accept that the exhausts have not budged one iota out of spec. in all that mileage and yet the intakes have gone daft, 0,2,3 and 4 thou doesn't sound very consistent either given that they have all gone through the same engine cycles I would have expected better consistency, not the sort of thing I've come accross on engines that I've had to bits.
If you take the head off don't be too alarmed at lateral piston movement when cold, they will move.
Check for a lip at the tops of the bores, if you drag a finger nail up them and it snags on a pronounced lip then thats not good, there should be hardly any, don't mistake it for carbon buildup though.
Dave
I seem to remeber someone writing in the Citroenian magazine about the problem of inlet valve sinkage. I was surprised at the time but I also recall the suggestion that the 1.7's were more afected.
terry - you have a car which starts and runs well. By all accounts the inlet valves have sunk and I for one would not describe this as an ideal state of afairs. Nevertheless it starts and runs and as you have seen from elsewhere on this board there are a number of people who would like an engine in that condition. I don't know how much you have spent on this car but my guess is that major work will probably come close to or exceed its cost. Accordingly replacement of the head will be something that you are reluctant to do. I would therefore adjust the valve clearances by re-shimming if possible and replace the cambelt unless you know how old it is, and then see what happens.
As an observation complaints of burnt valves on these engines are not common on this or other boards.
jeremy
terry - you have a car which starts and runs well. By all accounts the inlet valves have sunk and I for one would not describe this as an ideal state of afairs. Nevertheless it starts and runs and as you have seen from elsewhere on this board there are a number of people who would like an engine in that condition. I don't know how much you have spent on this car but my guess is that major work will probably come close to or exceed its cost. Accordingly replacement of the head will be something that you are reluctant to do. I would therefore adjust the valve clearances by re-shimming if possible and replace the cambelt unless you know how old it is, and then see what happens.
As an observation complaints of burnt valves on these engines are not common on this or other boards.
jeremy