Jump to content

  •  

Photo

Help! How Hard Are Camshaft Sprockets To Turn?


  • Please log in to reply
6 replies to this topic

#1 CRLS400

CRLS400

    New Club Member

  • Members
  • Pip
  • 9 posts
  • Model: LS400
  • Location: Please Select

Posted 06 April 2006 - 08:04 AM

Hello, I bought a used 92 LS400 and discovered that the timing belt idler pulley came apart and as a result the belt slipped and was pretty shredded by rubbing against the teeth. Before I replace the belt, I wanted to make sure the heads were okay (car may have overheated) so I tried turning the camshaft sprockets by hand with the timing belt removed (I cut it). They both turn clockwise a half an inch or so before I feel resistance that feels like a spring and they want to return to their prior position. Should they spin freely by hand or do you need to turn them with a socket and bar or release something else - I know they must turn in order to be able to set everything up when one replaces a broken belt. I don't want to force anything! Thanks!

Have something to contribute?

Sign in or register to start a topic...

 

#2 Ross W.

Ross W.

    Advanced Club Member

  • Regular Member
  • PipPipPip
  • 134 posts
  • Model: 1994 Lexus Ls400
  • Location: Please Select

Posted 06 April 2006 - 10:29 AM

Hello, I bought a used 92 LS400 and discovered that the timing belt idler pulley came apart and as a result the belt slipped and was pretty shredded by rubbing against the teeth. Before I replace the belt, I wanted to make sure the heads were okay (car may have overheated) so I tried turning the camshaft sprockets by hand with the timing belt removed (I cut it). They both turn clockwise a half an inch or so before I feel resistance that feels like a spring and they want to return to their prior position. Should they spin freely by hand or do you need to turn them with a socket and bar or release something else - I know they must turn in order to be able to set everything up when one replaces a broken belt. I don't want to force anything! Thanks!


I'm not sure if the 1uz engine is a non-interference design or not. If it is, you're feeling the resistance of the valve springs and hydraulic lifters, and a 1/2" drive wrench and the appropriate socket will overcome the resistance. If the engine is indeed an intereference design, and I keep hearing two schools of thought on this, what's happening is the valves are contacting the pistons, which is definitely a bad thing! Check the engine manual or Lexus on this before you do anything. If the 1uz engine is an interference design, the valves may already be bent; in that case the heads will have to come off and be rebuilt. Depending on the mileage, that may be a good idea anyway. In any case, replace the water pump, both idler pulleys of course, and check the power steering pump for leaks and excessive free-play on the shaft. Check out lexls.com for the timing belt replacement procedure.

#3 Shadow

Shadow

    Advanced Club Member

  • Regular Member
  • PipPipPip
  • 130 posts
  • Model: LS400
  • Location: Please Select

Posted 06 April 2006 - 11:01 AM

That engine in 92LS is non-interference, and as far as turning the camshaft, you will have to overcome many valve springs when turning the shaft so what you feel is normal. Turn the camshaft all you want and it won't hurt anything. BTW, what is the mileage?

#4 Leadfoot

Leadfoot

    Advanced Club Member

  • Regular Member
  • PipPipPip
  • 221 posts
  • Model: 92 & 98 LS400's
  • Location: Please Select

Posted 06 April 2006 - 02:58 PM

Yup, takes a lot of horsepower to operate the valve gear of most cars (except for rotaries!). Cams should only spin freely if something has sheared off!

While you have the belt off its an ideal time to change the water pump and idler pulleys, then you are good for AT LEAST 90K miles. Not to say something else won't need attention though....

Good luck.

#5 CRLS400

CRLS400

    New Club Member

  • Members
  • Pip
  • 9 posts
  • Model: LS400
  • Location: Please Select

Posted 06 April 2006 - 08:20 PM

Thanks a bunch for the replies - very good news that something's not wrong with the cams. Well tomorrow I will begin the dismanteling process and let you all know what I'm finding out along the way. I'm definately planning on changing out the belt, pulleys, tensioner, waterpump, crank and camshaft seals while I'm in there. I'll probably do the caps and rotors and plug wires as well. I got the car (it has 124,000 on the clock) for $1800 b/c it had been in a light front end accident and didn't run after that (guess the impact finished of the worn out idler bearing and the belt slipped when he tried to restart her after the impact) and the guy never took it to a mechanic - just bought a new Lexus SUV - so I'm still ahead of the game (unless I find out something else major is wrong). I really appreciate you all on this forum - thanks again.

#6 Leadfoot

Leadfoot

    Advanced Club Member

  • Regular Member
  • PipPipPip
  • 221 posts
  • Model: 92 & 98 LS400's
  • Location: Please Select

Posted 08 April 2006 - 03:00 PM

BTW I found out that I had power to both coils with the ignition on so the only thing not working was the fuel pump. However when I jumped the two terminals (FP and +B) on the check connector the fuel pump ran and pumped pressure. Do you think it's the EFI ECU? Thanks again.


The ECU will not let things activate if it detects that the cam position senors are not working, which is certainly the case with a stripped belt. Get everything aligned as per factory specs and you should be fine.

Check the engine mounts too, have heard of them shearing when the cars get a shunt.

Good luck!

#7 CRLS400

CRLS400

    New Club Member

  • Members
  • Pip
  • 9 posts
  • Model: LS400
  • Location: Please Select

Posted 08 April 2006 - 09:43 PM

Thanks for the further encouragement! Anyway, I ordered all the parts to do the multiple jobs and today I spent 5 hours disassembling everything. Fortunately, though some things were hard to get to, I got everything off/apart and now am waiting for the parts to arrive. I didcovered that not only was the idler bearing blown, but the water pump bearing was seized as well. My buddy had said that after the accident, the car was still running and he noticed that it was getting hot so he shut her off. It never started again. Both of us figured that the reason it heated up was b/c the electric fan housing had been broken in the accident and were stopping the fans from turning. I guess the reality was that power steering pump bearing was on its last legs and the impact finished her off, then the added heat/stress tore up the idler bearing which was going as well or vice versa. Does this seem like a plausible explanation? Anyway, we'll see how she goes on Tuesday or Wednesday and I'll let you all know what's up. Also, I checked the motor mounts and they were fine - thanks for the heads up!

Have something to contribute?

Sign in or register to start a topic...


Not what you're looking for?

Register now, we have a huge community of enthusiasts to answer any questions you might have