changed rocker arms and no compressions

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changed rocker arms and no compressions

Postby tinakersting » 01 Feb 2018, 21:46

Hi there,

My engine a 1990 2.1 dj vw t25 wxb needed new rocker arms after a nut fell off an adjuster on one of the rocker arms, last week. It had never had compression issues previously.
Since putting the new rocker arms on today the mechanic has said that the engine has no compression in any of the valves. We are at a loss as to understand why and so is the mechanic. Any ideas or suggestions?
cheers,
Tina
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Re: changed rocker arms and no compressions

Postby bigherb » 01 Feb 2018, 21:56

Either he has not adjusted the valves correctly or if he has they need to self-adjust, remove the spark plugs and spin the engine over with the starter motor for 30 sec or so to let them self-adjust.
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Re: changed rocker arms and no compressions

Postby tinakersting » 01 Feb 2018, 22:02

Thanks bigherb,
do you mean the adjuster screws on the rocker arms when you say valves?
I will definitely see if he has tried that when I speak to him tomorrow. It is a bit difficult to understand how an engine that was working fine, could have one nut drop off the adjuster screw on the rocker arm(which did drop out when the rocker cover was removed by the rac man) and then appear to be totally dead a week later.!!

thanks for the suggestion, Tina
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Re: changed rocker arms and no compressions

Postby T25Convert » 01 Feb 2018, 23:03

http://www.ratwell.com/technical/HydraulicLifters.html

This details all the mechanic should know but might not.....
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Re: changed rocker arms and no compressions

Postby kevtherev » 02 Feb 2018, 06:54

If the push rods are not seated correctly it will cause an always open valve
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Re: changed rocker arms and no compressions

Postby itchyfeet » 02 Feb 2018, 07:43

Once you have changed rocker arms you need to do the basic adjustment of just touching then 2 turns.

Preload of 2 turns means your valves are temporarily open

What no manual tells you is that you then have to wait, it can be as little as 1 hour, it can be a few hours for the hydraulic tappets to return to equilibrium and the valves to close.

the slower they close the better your tappets are.

if you wait just one hour it will probably start but be rough for a while because it's not running on all four.

as said it's common mistake to not get push roads seated, in this case you can chip lumps off the tappets, for this reason I now use a USB camera to check

view down push rod tube with USB camera showing pushrod correctly seated
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Re: changed rocker arms and no compressions

Postby tinakersting » 02 Feb 2018, 10:19

thanks for your information chaps, its been very helpful. On further inspection the valves on the other side of the engine have been damaged by the rocker adjusters being too tight . AND so if the mechanic restores the head of the engine, he says who knows what strain that might exert on the block of the engine so it looks like we are heading towards a reconditioned engine going in as a replacement for the reconditioned engine that has failed at 38000 miles.
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Re: changed rocker arms and no compressions

Postby itchyfeet » 02 Feb 2018, 10:38

tinakersting wrote:thanks for your information chaps, its been very helpful. On further inspection the valves on the other side of the engine have been damaged by the rocker adjusters being too tight . AND so if the mechanic restores the head of the engine, he says who knows what strain that might exert on the block of the engine so it looks like we are heading towards a reconditioned engine going in as a replacement for the reconditioned engine that has failed at 38000 miles.



most 'reconditioned' engines are really just repaired engines with minimal new parts, 40,000 miles is probably not unreasonable.
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Re: changed rocker arms and no compressions

Postby T25Convert » 02 Feb 2018, 11:33

So you had a van that ran fine and you were happy with the performance? Then it spat out a nut on one adjuster, which damaged one rocker arm on one cylinder.

Your mechanic has replaced the rockers, and now can't get any compression on any cylinders.

Now you need a new engine.

Do you trust your mechanic? I think I'd be after a second opinion before you shell out on a reconditioned engine....
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Re: changed rocker arms and no compressions

Postby itchyfeet » 02 Feb 2018, 12:58

Dare I suggest the mechanic could have not centered the pushrods and this can cause damage I have been told.
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Re: changed rocker arms and no compressions

Postby T25Convert » 02 Feb 2018, 13:47

itchyfeet wrote:Dare I suggest the mechanic could have not centered the pushrods and this can cause damage I have been told.


Not centering the push rod makes it around 5mm longer - I know as I managed to do it (more than once). If you wind the adjuster screw all the way out, the valve is still open as the push rod is long enough to still operate the rocker a little.

With the screw in a nominal 'two turns' I suspect it would hold the valve open wide throughout the cycle (giving zero compression).

It may or may not lead to damage, depends what is done next. Spinning it on the starter might cause a bit of valve-piston interaction.

However, if the mechanic is messing around trying to work out valve lash, then he may have observed the never closing valves and assumed that this is because the valve seats have regressed or valves stretched (hence his 'tight valve' diagnosis) rather than the push rods not seated.

I'd definitely want a second opinion.
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Re: changed rocker arms and no compressions

Postby tinakersting » 02 Feb 2018, 17:57

T25Convert wrote:
itchyfeet wrote:Dare I suggest the mechanic could have not centered the pushrods and this can cause damage I have been told.


Not centering the push rod makes it around 5mm longer - I know as I managed to do it (more than once). If you wind the adjuster screw all the way out, the valve is still open as the push rod is long enough to still operate the rocker a little.

With the screw in a nominal 'two turns' I suspect it would hold the valve open wide throughout the cycle (giving zero compression).

It may or may not lead to damage, depends what is done next. Spinning it on the starter might cause a bit of valve-piston interaction.

However, if the mechanic is messing around trying to work out valve lash, then he may have observed the never closing valves and assumed that this is because the valve seats have regressed or valves stretched (hence his 'tight valve' diagnosis) rather than the push rods not seated.

I'd definitely want a second opinion.
Well it seems that the rocker arms on the side of the engine that have not been changed have damaged valves due to the rockers being too tight and there is some compression on the side where the nut fell off but it is low. The mechanic says if he has to renew the cylinder heads on the side with the damaged valves it will mean the lower half of the engine will have undue pressure on it so that would need to be rebuilt. He had quoted a sum of three thousand pounds to recondition the whole engine. He dosent do log though so even more to get that reinstalled we are very sad


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Re: changed rocker arms and no compressions

Postby tinakersting » 02 Feb 2018, 17:58

tinakersting wrote:
T25Convert wrote:
itchyfeet wrote:Dare I suggest the mechanic could have not centered the pushrods and this can cause damage I have been told.


Not centering the push rod makes it around 5mm longer - I know as I managed to do it (more than once). If you wind the adjuster screw all the way out, the valve is still open as the push rod is long enough to still operate the rocker a little.

With the screw in a nominal 'two turns' I suspect it would hold the valve open wide throughout the cycle (giving zero compression).

It may or may not lead to damage, depends what is done next. Spinning it on the starter might cause a bit of valve-piston interaction.

However, if the mechanic is messing around trying to work out valve lash, then he may have observed the never closing valves and assumed that this is because the valve seats have regressed or valves stretched (hence his 'tight valve' diagnosis) rather than the push rods not seated.

I'd definitely want a second opinion.
Well it seems that the rocker arms on the side of the engine that have not been changed have damaged valves due to the rockers being too tight and there is some compression on the side where the nut fell off but it is low. The mechanic says if he has to renew the cylinder heads on the side with the damaged valves it will mean the lower half of the engine will have undue pressure on it so that would need to be rebuilt. He had quoted a sum of three thousand pounds to recondition the whole engine. He dosent do log though so even more to get that reinstalled we are very sad


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Re: changed rocker arms and no compressions

Postby T25Convert » 02 Feb 2018, 18:27

tinakersting wrote:
T25Convert wrote:
itchyfeet wrote:Dare I suggest the mechanic could have not centered the pushrods and this can cause damage I have been told.


Not centering the push rod makes it around 5mm longer - I know as I managed to do it (more than once). If you wind the adjuster screw all the way out, the valve is still open as the push rod is long enough to still operate the rocker a little.

With the screw in a nominal 'two turns' I suspect it would hold the valve open wide throughout the cycle (giving zero compression).

It may or may not lead to damage, depends what is done next. Spinning it on the starter might cause a bit of valve-piston interaction.

However, if the mechanic is messing around trying to work out valve lash, then he may have observed the never closing valves and assumed that this is because the valve seats have regressed or valves stretched (hence his 'tight valve' diagnosis) rather than the push rods not seated.

I'd definitely want a second opinion.
Well it seems that the rocker arms on the side of the engine that have not been changed have damaged valves due to the rockers being too tight and there is some compression on the side where the nut fell off but it is low. The mechanic says if he has to renew the cylinder heads on the side with the damaged valves it will mean the lower half of the engine will have undue pressure on it so that would need to be rebuilt. He had quoted a sum of three thousand pounds to recondition the whole engine. He dosent do log though so even more to get that reinstalled we are very sad


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I think you might be being taken for a ride.

Did it run okay before the nut fell off?
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Re: changed rocker arms and no compressions

Postby tinakersting » 02 Feb 2018, 19:13

T25Convert wrote:
tinakersting wrote:
T25Convert wrote:[quote="itchyfeet"]Dare I suggest the mechanic could have not centered the pushrods and this can cause damage I have been told.


Not centering the push rod makes it around 5mm longer - I know as I managed to do it (more than once). If you wind the adjuster screw all the way out, the valve is still open as the push rod is long enough to still operate the rocker a little.

With the screw in a nominal 'two turns' I suspect it would hold the valve open wide throughout the cycle (giving zero compression).

It may or may not lead to damage, depends what is done next. Spinning it on the starter might cause a bit of valve-piston interaction.

However, if the mechanic is messing around trying to work out valve lash, then he may have observed the never closing valves and assumed that this is because the valve seats have regressed or valves stretched (hence his 'tight valve' diagnosis) rather than the push rods not seated.

I'd definitely want a second opinion.
Well it seems that the rocker arms on the side of the engine that have not been changed have damaged valves due to the rockers being too tight and there is some compression on the side where the nut fell off but it is low. The mechanic says if he has to renew the cylinder heads on the side with the damaged valves it will mean the lower half of the engine will have undue pressure on it so that would need to be rebuilt. He had quoted a sum of three thousand pounds to recondition the whole engine. He dosent do log though so even more to get that reinstalled we are very sad


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I think you might be being taken for a ride.

Did it run okay before the nut fell off?[/quote]At least taken for a ride is transport of some kind!
The thing is I am not mechanically minded at all we have learned the hard way that owning a t25 if you are not a mechanic or a hobby enthusiast IS expensive. Either that or none of the various mechanics we have used have been very interested in doing a decent job
The jist of this latest episode is that two weeks ago as I was shutting the engine off having driven from leiston to lowestoft my partner noticed a rattling noise never previously heard coming from the engine. Not knowing if we were causing Any damage and not wanting to chance any further damage we called the rac.
The chap used his long screwdriver as a stethescope(old school apparently) and after removing the driver side rocker cover the nut from one of the adjuster screws fell out onto the tarmac.
We were recovered to a garage in norwich.
When the mechanics inspected the engine they told us that the rocker adjusters had been left too tight by the person who had last adjusted them and some of the rocker arms were damaged and needed replacing. THEY were not able to source the parts.
I asked on the forum on Sunday and a member offered a compatible set complete which I took to them on wednesday
BY Thursday they reported that having changed the rockers on the side that cast the nut there was no compression in ANY of the engine valves.We found this hard to believe. Prior to the nut shedding we had never had a problem with power.
Today the mechanic says that the valves on the other side have been damaged by the too tight rockers and one valve is even in danger of falling down through the damaged collar which has been damaged over time. HE SAYS if he reconditions this top part of he engine it will more than likely cause the lower untouched side of the engine to fail fairly quickly hence he suggests he totally reconditions the whole engine or we purchase a newly reconditioned engine which he would put in for about three thousand pounds.
We do not know what to do. A member suggests a second opinion, are there any vw mechanics who know their t25s in Norwich who we could have the van transported to to give us that second opinion?
THIS mechanic has given a lot of time to us this week but has no other practical options for us.

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