patrol gu tb45e engine knocking badly!!!!!

Submitted: Sunday, May 20, 2007 at 18:39
ThreadID: 45694 Views:8512 Replies:6 FollowUps:4
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hey guys,

i know this question may have been answered before, and i have tried to find the post, but no luck!

i have a 97 gu patrol which i converted to lpg 2 and a half years ago. since then, it's been fine.

3 months ago i went to start it up, but there was 'compression' on the valves. finally got it started with a massive knocking sound coming from the engine.

had it towed to nissan in randwick, where they found the push rods were bent and tappet number 1 was gone.

after $560 i got the patrol back and it was ok, up until 2 weeks ago!!!
same problem as before. nissan had it in for a week and a half, and said they had to go right down to the cylinder block. this then had to be sent away to a 'specialist'.
they replaced the valves, reseated the rockers, and a heap of other stuff. after $2600 i was back on the road.............for 4 days!!!!
back to square 1!!!

now nissan are saying that the cams have bent the push rods, and they need to keep it in until fixed.
i have protested to the dealer that i will not be paying for the rectifications as it should have been done in the first place.

first question: has anyone else had this problem, and what has been done?
second question: as the first major repair was a failure, would you pay for the new repairs?
third question: would you consider the lpg conversion to be a factor, even though the petrol to lpg refill ratios (1:5) were kept to?

any (relevant) feedback would be greatly appriciated!lol

cheers

ps. in hindsight, i should have bought a reconditioned engine installed,
and when i got the car back, i immediately test drove the new navara!! very nice:)
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Reply By: nowimnumberone - Sunday, May 20, 2007 at 19:04

Sunday, May 20, 2007 at 19:04
did they tell you why the push rod was bent ?
unusual for a tappet to be gone
has the head gasket been checked for leaks that could cause compression lock?
cheers

AnswerID: 241233

Follow Up By: contains_nuts - Sunday, May 20, 2007 at 19:06

Sunday, May 20, 2007 at 19:06
yeah, push rod was bent due to the cam......apparently!
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FollowupID: 502126

Follow Up By: Exploder - Sunday, May 20, 2007 at 19:16

Sunday, May 20, 2007 at 19:16
A cam doesn’t bend a push rod on it's own.

Your engine timing it ether shot to hell
The push rods are the wrong length
Clearances are way over adjusted.

Either way you should have more damage than just a bent push rod
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FollowupID: 502129

Follow Up By: contains_nuts - Sunday, May 20, 2007 at 19:25

Sunday, May 20, 2007 at 19:25
initially, when i had the first repair done, nissan said that the valves had siezed and caused compression, and when they came free, the force going through was too much, also knocked two rockers off
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FollowupID: 502131

Follow Up By: Exploder - Sunday, May 20, 2007 at 21:08

Sunday, May 20, 2007 at 21:08
Re reading you post with the info provided, It sounds like something in you valve train is not set up correctly as all the cam is doing is pushing up on the lifters which forces the Push rods up that actuates the rockers and valves, so a stock cam fitted to stock Push rods and vale train can’t be the issue.

My only guess is something is so out of wack that you valve springs are hitting full compression and the cam still hasn’t hit full lift yet= something braking/ bending in your case a few pushrods.

I would have gone with engine timing being out except it went for 4 days and if you timing was out enough or slipped enough to cause bent push rods you would also likely have smashed pistons bent valves. Ect

In any case its Nissan problem as the Pulled the motor down they fixed the Issue that they diagnosed to be sized valves (I am a little confused with that one) then reassembled it incorrectly.

Bottom line they didn’t just replace a spark plug, they striped the engine and reassembled it and buy the sounds of it incorrectly.
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FollowupID: 502174

Reply By: Barnray - Sunday, May 20, 2007 at 21:05

Sunday, May 20, 2007 at 21:05
Compression on valves !!!!!! somebody is feeding you B/s, It sounds very much like the valve timing has slipped and the piston has kissed the valves which will give all of the symptoms and the damage described. I would be ringing the MTA and asking for their advise on the situation. Barnray
AnswerID: 241260

Reply By: 120scruiser (NSW) - Sunday, May 20, 2007 at 21:50

Sunday, May 20, 2007 at 21:50
XE and XF falcons used to do this for no apparant reason.
I have had a 4.5 Patrol on LPG wear the rocker gear out due to lack of maintenance and the sludge blocked up the oil gallery. It didn't bend a push rod though. Remember in an LPG engine the valves do run dry and it is a possibility that they may have become tight and whilst the cam lobe attempts to raise the push rod, the valves are tight and hence bending. It can happen but should have been rectified whilst the engine was stripped.
The only other reason for bending push rods is timing being way out but it would drive like a pig, hard to start and not run good for 4 days.
Has it been backfiring by any chance? Pre detonation is a bad thing in LPG engines and can do all sorts of damage.
Sounds like you are having a bit of bad luck.
Hope your day improves.
Scott
AnswerID: 241280

Reply By: contains_nuts - Sunday, May 20, 2007 at 21:56

Sunday, May 20, 2007 at 21:56
thanks for your input guys,

i think, you're right, the MTA is the next step. i'm probably getting muddled up with the compression/siezure bit! lol (not too mechanically minded!)

if the fuel injectors aren't operating, could this have caused the valves to stick?

cheers

AnswerID: 241284

Reply By: Member - DOZER- Monday, May 21, 2007 at 19:29

Monday, May 21, 2007 at 19:29
Has the gas ever gave you backfires?? IF the key that drives the cam gear from the crank is sheared or loose, or the gears are worn....the slack will allow piston to valve contact.
Now you will get nowhere arguing in court, because you have modified the vehicle....the only people in court that win are the lawyers....
Tell the service manager that he should have looked for cause the first time, he definately was negligent not looking for cause the second time...and now he has to find out why and fix it... Tell him you know what your on about more than him, and the valves have been hitting the piston causing the damage....not all that fairy stuff about aliens causing it....
AnswerID: 241448

Reply By: contains_nuts - Wednesday, May 23, 2007 at 17:37

Wednesday, May 23, 2007 at 17:37
ok........got my car back!.......

apparently the lifters were causing the 'main' problem, causing the push rods to bend.
nissan said straight away that they would only charge me for the parts ($675) and not the labour, which is fair i suppose. so i haven't involved the MVA. initially they were going to charge me for the push rods too! but i reminded them that they had only been replaced in February this year.

overall a good result! :)

thanks again for all your suggestions/advice.
AnswerID: 241878

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