big end on a diesel xantia?

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heath robinson
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big end on a diesel xantia?

Post by heath robinson »

At 120k my xantia has started a new noise at below 1400rpm. the noise is metallic and is similar though louder than the rattle of a worn box when in neutral on tickover. The noise is though still there when the clutch is depressed. It is definitely from the engine and loudest when under the car. From in the car, it is similar to the vibration of a failed engine mounting. I've had big ends go before on a vw and a triumph and they were a nastier noise than this one. also the oil pressure still seems good. oil light will go out on starter. i drive the car gently and change the oil and filter every 6k. i also always let the car tickover before driving off. possibly it was neglected before my ownership 16k ago?
to preclude the hydraulic pump, i have taken the drivebelt off and run the car; noise still there.
other possibilities:
fitted recon injectors 1000 miles ago. could 1 be faulty and cause knocking? surely there would also be smoke out the back though on tickover?
could it be cambelt tensioner or idler packing in?
not sure what to do with this one as will also require a screen due to 20mm star in vision and an offside wheel sensor for test.
thanks for your thoughts
regards
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AndersDK
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Post by AndersDK »

Have you checked the coldstart device ?
This is NOT a fuel enricher - but a timing modifier.
When these begin to stop functioning owners often modify the idle setting to get DOWN the idle revs.
If the injection is constantly running on a slightly different timing (even caused by wear in pump) the engine will certainly sound different - mainly with a more distinct diesel knocking.
heath robinson
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Post by heath robinson »

thanks v much; interesting information, i had no idea it changed the timing; i'd guessed it just increased the revs. the tickover as i recall has always dropped from 950ish cold to 750ish when warm. i have not noticed the tickover as any different either hot or cold over the year i've had the car. would this indicate the cold start is working ok? the noise appears to have come on quite quickly ie over a couple of days, if this lends anything to diagnosis. i suppose the key test would be to mark where the pump is at present, then to run the engine and gradually move pump to discount timing? unfortunately it would not surprise me if the pump is duff as the car has always been a bit of a thirsty slug (36mpg round town and motorway at 85)
fabulous forum thanks
CommY
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Post by CommY »

To rule out the injectors loosen the fuel input union on each injector in turn and see if the knocking disappears at any point.
Don't know what a knackered water pump bearing sounds like on a Xantia but could this be it??
You have also f-ed crank bearings to consider.
When you take up the engine slack when setting off and release the clutch does the knock quieten? More knock under load or less?
Dave Bamber
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Post by Dave Bamber »

Could be the chain drive on the oil pump, if they get realy slack the chain can rettle against the block.
citronut
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Post by citronut »

air in fuel system makes them knock,pump timing should not alter notisably with cold start,it certanly shoul not move on its owen other than with cold start regards malcolm
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Post by citronut »

ps maybe you should get cam belt timing checked by some one that knows what they are doing if fuel consuption is to high and no get up and go, there is defenatly some thing not set up right regards malcolm
JohnT
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Post by JohnT »

Is the noise constant with engine speed? It does not sound like a big end problem which a definate repetitive deep thud when the piston is driven down on the firing stroke.
If an injector was meeting the piston head the noise would be constant, it would not go away at speed. You say noise is below 1400 which suggests it then dissapears above 1400?
As for your screen, shop around...there are some silly prices out there. I paid £105 plus VAT including fitting.
citronut
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Post by citronut »

injectors cant meet piston because they are behind pcb which is fitted in head face regards malcolm
john alexander
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Post by john alexander »

In reply to anders post I contacted Bosch for advice on the cold start device,ie advancing the pump timing.Their reply was that the cold start system had no effect on the timing of the pump,but only raised the revs. regards john
heath robinson
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Post by heath robinson »

Thanks to all for your thoughts.
I will try the injector test; though wouldn’t it smoke if injector duff?
Water pump an interesting thought; though don’t they leak when the water pump bearings go? This would be the sort of thing I would guess at due to the ok oil pressure and the instant switch from noise to silence when the revs increase. Indeed before looking, I had guessed possibly the crank pulley loose and running smooth once the speed had increased.
I’m thinking big ends usually go before crank main bearings?
Will have to experiment on the set off; what is your thinking on what it would rule out or in?
Interesting thought on the oil pump chain, I had no knowledge of this; guess the only way to check is remove the sump. Odd that the noise came on very quickly though; ie couple of days.
The cam belt timing is ok. Performance also the same for pre and post belt change. The car will also cruise comfortably at 100, probably more.
Yes, nice and smooth and quiet above 1400 rpm; instant end to noise as revs build.
Screen £105 would be fantastic; I’ve been quoted £188 due to the need to replace the seal? Was it a national company?
Fantastic body of knowledge and ideas out there. Thanks to all.
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JohnW
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Post by JohnW »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by heath robinson</i>

Thanks to all for your thoughts.
I will try the injector test; though wouldn’t it smoke if injector duff?
Water pump an interesting thought; though don’t they leak when the water pump bearings go? This would be the sort of thing I would guess at due to the ok oil pressure and the instant switch from noise to silence when the revs increase. Indeed before looking, I had guessed possibly the crank pulley loose and running smooth once the speed had increased.
I’m thinking big ends usually go before crank main bearings?
Will have to experiment on the set off; what is your thinking on what it would rule out or in?
Interesting thought on the oil pump chain, I had no knowledge of this; guess the only way to check is remove the sump. Odd that the noise came on very quickly though; ie couple of days.
The cam belt timing is ok. Performance also the same for pre and post belt change. The car will also cruise comfortably at 100, probably more.
Yes, nice and smooth and quiet above 1400 rpm; instant end to noise as revs build.
Screen £105 would be fantastic; I’ve been quoted £188 due to the need to replace the seal? Was it a national company?
Fantastic body of knowledge and ideas out there. Thanks to all.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
I can't buy in much here, but it doesn't sound like a big end to me. Sound terrible on idle and it gets much worse in my limited experience as revs rise, and as for oil pressure......
Also there's a considerable difference in sound between a reciprocating rattle and a rotating rattle or the light noise of a slack chain.
Have you done the old-fashioned thing and tried to find where the noise is coming from with a large screwdriver - pressed against different places with your ear against it - used like a doctor's stethoscope? Be very careful to keep it away from high tension leads (to spark plugs for example) as 40,000 volts is bad for ears.
Good luck
JohnW
heath robinson
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Post by heath robinson »

sorted!
11000 miles since the cam belt was changed the crank pulley had worked loose? had not come far undone and still required a socket to undue it, probably due to studlock. absolutely fantastic; the cheapest possible fault. i was heading south towards the belt pulley based on noise. i was able to narrow down by sound through the use of a stethoscope! a mate very kindly offered to lend me his car as mine was rattling so badly. he happens to be a doctor and by chance had left a stethoscope in the back. fantastic for noise location, particularly if you pull the end off and use the basic tube and move it around. it was only when i was starting to remove the crank pulley that i thought it didn't take much of a tug. i had been perplexed by the prospect of a big end given how well i look after the engine. thanks once again for your help. this forum is fabulous and has some excellent contributors. i also changed the cam cover gasket based on discussion here. getting ready for the test now; dreading the cost of a screen. anyone got a front abs sensor they wish to sell?
thanks again for your pointers
regards
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