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Re: Hydraulic tappets

Post by Philhod » 06 Jul 2011

If there are wear ridges appearing in the cam lobes then it is ready for renewing.

If it's perfectly smooth just fit yer new tappets. :)
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Re: Hydraulic tappets

Post by mat_the_cat » 06 Jul 2011

Makes sense to me - if something is visibly worn then that's fair enough. Once I have the rocker cover off, if the cam is that worn then I'll just put the cover back on until cash (or a cam) comes my way!

Was just worried about them bedding together to such an extent that it would fuck my new tappets up within a short time of putting them in, but I can't really see that happening.
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Re: Hydraulic tappets

Post by Philhod » 06 Jul 2011

As far as I can remember it was drilled into me that manufacturers made shafts and details such as tappets, shims, rocker rubbing blocks, were all around the same Brinnel number.

Never checked any though :P
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Re: Hydraulic tappets

Post by mat_the_cat » 06 Jul 2011

I should imagine that putting a large Brinell indentation on the face of a tappet would fuck it up quite effectively!
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Re: Hydraulic tappets

Post by Philhod » 06 Jul 2011

There are small ones :lol: Materials are supplied with cast letters so they can be traced back in case of failiure. Once samples are tested that covers the whole batch.
Weld tests are done the same way.
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Re: Hydraulic tappets

Post by mat_the_cat » 07 Jul 2011

The way we usually used to test hardness was the Rockwell method (quicker, and easier to get a false low reading). Chances are the hardness impressions are ground off after heat treatment anyway.
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Re: Hydraulic tappets

Post by Philhod » 07 Jul 2011

:) Test samples are rarely used and testing done after H/T. Camshafts are tested on the unmachined side of different cams as each batch is completed. Q/a used to ask for around 5% tested.
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Re: Hydraulic tappets

Post by docchevron132 » 08 Jul 2011

what tends to fuck them is if you reuse tappets with the same cam but in the wrong order from disassembly.
If you're fitting new it should be fine, they'll just bed in tot he cam.
I've replaced millions of tappets int he past and reused the cams, NEVER had a problem of failure yet, and some of those engines went on for another 1/4 million miles, others are still going.
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Re: Hydraulic tappets

Post by Philhod » 08 Jul 2011

Very true Doc.

I think what Mat is concerned about you highlighted there as it applies to shimmed or hydraulics. If you use previously used gear it sometimes can have become work hardened and, to some extent that would wear affect new stuff that hasn't had any wear yet.
With yer new tappets on a used cam it would, therfore tend to wear the tappet rather than the cam albeit on a very small scale. 8)
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Re: Hydraulic tappets

Post by docchevron132 » 09 Jul 2011

not sure I'd be worried about that, if they wear enough to go through the hardening before they work hrdened they were shit to start with!
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Re: Hydraulic tappets

Post by mat_the_cat » 15 Jul 2011

On a related theme, I have a question about cam/injector pump timing. The engine has one belt at the front which drives the camshaft and water pump, and another from the back of the camshaft which drives the injector pump. Timing is advanced when cold with a manual knob.

A while back I changed the cam belt and tensioner (injector pump belt was fairly recent). I planned to replace the water pump with a genuine VW I picked up cheap, but the pulley was a slightly different diameter, and I could not get the belt teeth to fit exactly without moving the crank or cam. As the pump wasn't leaking and looked newish I left it on there and timing was unaltered. Performance and starting were identical.

Last year I needed to replace the rear cam seal, injector pump belt and some seals on the pump. The pump (Bosch VE) was so far rotated on its mountings that a couple of the slotted holes didn't line up, and hence only being held on by 2 bolts (not 4). Hence I couldn't replace the pump exactly where it came from. It got more complicated when I took the rear cam pulley off to change the seal, and found the pulley wasn't keyed to the shaft in any way - it rather made me wish I'd marked it better!

Anyway, got it started and timed it by ear. However, I suspected it was slightly retarded (like its owner) as it would start instantly with the advance knob out; with it in it would take a couple more revolutions to catch, run a little smokily for a while and I think mpg was slightly down. So I left it pulled out all the time.

I took it for an MOT this year and got them to adjust the timing to the book setting (I didn't have anything to mount the DTI on, and I didn't know the correct measurement). They reckoned it was almost spot on (yay me) but advanced it very slightly. Sure enough, it now sounds knockier. BUT, if I leave the advance knob in, it cranks over for a few revolutions before smokily catching - it didn't do this before I changed the injector belt. Pulling out the advance lever again gives perfect starting.

Not sure of the effect on mpg yet but my guess is it's thirstier - power seems down too, I seem to be in a gear lower than normal. After all that explanation, my guess is that the water pump was changed at some point for one with the wrong sized pulley, altering the cam and injector timing. The injector pump was then adjusted as far as it could go, so it ran OK. I changed the injector belt and set it up reasonably OK. Now the injector pump is timed correctly to the crank, but not the cam.

Does that sound plausible? Seeing as I have to take the cam out to do the tappets, I can check it I guess - the garage will lend me all their tools for checking it (the front cam pulley is also not keyed to the shaft). The only thing I don't understand is that if advancing the timing by moving the pump has made things worse, why does advancing it further with the cold start knob make it better?
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Re: Hydraulic tappets

Post by Philhod » 16 Jul 2011

wrong water pump pulley won't alter cam or injector timing if they are set in conjunction.
All it would do is, make the w/pump go round faster or slower 8)
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Re: Hydraulic tappets

Post by docchevron132 » 17 Jul 2011

true, but, if when fitting the belt after replacing the waterpump he cam and or crank wasn't locled, it's entirely plausable that witha different diameter pulley on the waterpump the timing betwixt cam and crank could have altered during fitting.
In which case, if the inj pump is timed ok against the cam but it still runs off, it seems entirely likely the cam timing could be a theoretical "tooth" out, which would cause the same symptoms.
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Re: Hydraulic tappets

Post by Philhod » 17 Jul 2011

:) True enuff but then I never replace the belt unless I have everything locked up. :wink:

Mind you thinking about it. There may be different sizes of pulley, because, when I have done belts in the past, some have gone on relatively easily. Whilst others have taken up nearly all the tensioner adjustment, being really stiff to get on. [chin]
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Re: Hydraulic tappets

Post by docchevron132 » 17 Jul 2011

that and we dont know whats been done to this engine in the past!
1989 BX 17TD P2 Hybrid
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1971 BL 350FG ambulance
1993 Dennis Lance 132 It's got mahooosive hairy bollocks!


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Re: Hydraulic tappets

Post by Philhod » 18 Jul 2011

:lol: :lol: Yeah, and the owners always say Oh it's never been touched before....yeah right.!!
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Re: Hydraulic tappets

Post by mat_the_cat » 18 Jul 2011

docchevron132 wrote:true, but, if when fitting the belt after replacing the waterpump he cam and or crank wasn't locled
I'm guessing that nothing was locked as to lock the crank you need to make up or buy a toothed bracket that fits onto the flywheel, and there appears to be no way of locking the cam without removing a pulley. Given that to repair the leaking rear cam seal they smothered it in silicone I very much doubt they did anything properly!

I know that the water pump pulley size would only affect the speed of itself running, but as the tensioner is on the opposite belt run, if I had put a genuine VW pump on the only way to ensure tension on the water pump side of the belt run would have been to shift the cam or crank round half a tooth
docchevron132 wrote:if the inj pump is timed ok against the cam but it still runs off
The pump is timed to the crank, but may or may not be timed to the cam now.
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Re: Hydraulic tappets

Post by Philhod » 18 Jul 2011

It's a long time since I did a VW motor and it was an early PD. This engine has a hole in the flywheel at no1 TDC, just like the XUD, but I think the rod goes in from the g/box side.
Once you have set the belt tension, before starting, if you do 4 complete revolutions by hand, (just put some chalk on the belt to know when it's round) It equals out the tension in the belt on all runs :wink:
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Re: Hydraulic tappets

Post by docchevron132 » 19 Jul 2011

still points towards it being out of timing though, from everything you've said!
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Re: Hydraulic tappets

Post by Philhod » 19 Jul 2011

:) Err... yeah! wat ee sed.
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