Technical Identifying a dead hydraulic tappet - 899cc motor

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Technical Identifying a dead hydraulic tappet - 899cc motor

Threebox

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I have just removed the rocker shaft from our 21,000 mile P-reg 899cc Cinquecento SX to check the dreaded noisy hydraulic tappets and I can see that some are 'shorter' than others - see photo.

Is this because something internal has collapsed, like a spring? I'm assuming the 'shorter' ones are dead and need to be replaced.

Any inside knowledge gratefully received!
 
The tappets are supposed to be self-adjusting. They fill with oil (I think you should fit new ones "pre-filled") and then as they are squeezed by the rocker arm during use, the end-cap is compressed and that forces oil out until the tappets are the right effective length to float on the rocker arm.

As there is wear, the spring is always trying to press the cap outwards, so the tappet will self-adjust. The void behind it is filled with oil, which gets sucked in, to maintain the new effective length.

Make sure the old tappets don't have a blocked oil channel and make sure that the end-cap is not jammed. I doubt it's a collapsed spring.

If you dismantle the tappet you may find a spring and also a ball bearing which can be tricky to re-assemble, so buy new tappets unless they're a horrific price.


Ralf S.
 
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We acquired the SX 4 or 5 weeks ago from an elderly couple who bought it when it was a few months old. It had been off the road for 7 years after health issues stopped the wife driving, but the husband had got it MOT'd and ready to go back to everyday use. On a test drive it was noticeably tappety but I felt I could probably resolve that issue.

I quite quickly changed the oil for Shell Helix 15W40 with a new filter hoping that would make a difference but it didn't cure the problem. About two weeks ago I added Wynn's Hydraulic Lifter treatment and have run the car about every day since then without the noise changing discernibly. Next step is obviously to swap the tappets but as you say, perhaps I should have tried a more aggressive flushing to try to get them working again! I found a thread on the diesel treatment - is it still worth doing?

I have some new tappets which seem to be an updated version of the ones on the car. They have a swivel end with small oil holes which I'm assured by the supplier are OK for the car - I think my best plan is to offer them up, prime with fresh oil and see how they go.

Thanks for your advice.
Jonathan
 
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well,

I'd heard of a coolant flush- but I didn't know there was enough 'lubricity' (made up word) in diesel, to run an engine on it.

I suppose it mixes with the residual oil left in the cam-gallery & suchlike...
 
Funny you should say that...

I just tried it and it seems to be about 1mm narrower than the rocker bore - not ideal!
I'll have to swap for the correct ones.

Will report back.
 
True. No pre-load adjustment is possible. The parts guy is sending me the correct set.

J
 
True. No pre-load adjustment is possible. The parts guy is sending me the correct set.

J


if you end up getting tired of he hydraulic tappets, just look round for a rocker shaft from a fiat panda or uno or a112 903cc engine and just have tappets that you can adjust instead. I think i fitted one to our 1994 cinq in about 1998 and it worked fine, just use the valve gap settings from the engine model that supplies the rocker shaft. 0.4mm inlet and 0.45 exhaust if i remember correctly, please do check for yourself though.

Tim
 
True. No pre-load adjustment is possible. The parts guy is sending me the correct set.

J


if you end up getting tired of he hydraulic tappets, just look round for a rocker shaft from a fiat panda or uno or a112 903cc engine and just have tappets that you can adjust instead. I think i fitted one to our 1994 cinq in about 1998 and it worked fine, just use the valve gap settings from the engine model that supplies the rocker shaft. 0.4mm inlet and 0.45 exhaust if i remember correctly, please do check for yourself though.

Tim
 
Thanks everyone for your advice. I got a replacement set of hydraulic tappets and fitted them this afternoon. I primed them with oil and re-torqued the rocker shaft before refitting the cover with a new gasket.
On start-up the tappets chattered until the engine warmed up and then got quieter. There were no leaks. I left the car for an hour and then took it for a drive and the tappet noise has gone (for now...).
It’s so much more restful to drive without worrying about potential wear or damage.
If this set of tappets doesn’t last I might look for a manual adjustment option. In the meantime we’ll have some fun with it!
Jonathan
 
Has anybody else ever tried that...?
Yes I put the manual rocker assembly from a Panda on my 1994 899 Cinq.
Mine originally had the early hydraulic rockers with adjusters on the other end.
The pure mechanical Panda setup was A LOT quieter.

I'd expected them to need frequent adjustment, but they stayed quiet and I never touched them again. They are still going over 10-years later.
 
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