Bent Valves

[MikeC218]

New here but have been reading the posts for my 2000 Lx470, thanks for the past help.

I noticed my pulley tensioner was rattling so I replaced the pulley thinking it was out of balance. It seemed fine, so I went to the store and on the way back, the car dies, I coast into a gas station and pop the hood. The belt had jumped off the crankshaft pulley and pushed it back toward the engine. The belt is now on the Harmonic Stabilizer. Instead of replacing the pulley myself I called my local guy to tow it into his shop and repair it. He installed a new pulley, and the car would not start. He replaced the spark plugs and it would not start. Then he tells me that plastic from the pulley braking got into the timing belt housing and made it jump 6 teeth. His final diagnosis was bent valves.

So, I performed a compression test and all of the cylinders came up with 88 to 90 PSI. Is this possible? I know the readings are low but is there another reason for all of them to be this low and consistently the same PSI?

 

[2001LC]

What you see on front of engine has nothing to do with timing belt. You see drive belt which runs VAN pump, A/C compressor and cooling fan. Jumping a drive belt will not effect the valves.

Compression is taken with engine hot. Cold will show lower compression. Cold compression of 88 to 90 PSI on all 8, I'd say your cylinders are fine. Spec is within 14 PSI of each other. Your below min at 90 PSI, but min is spec'd for normal operating temp.

You likely damaged crank sensor wire or even cam senor wire. They sit on left side of engine up front near drive belt. Often not routed and tied down properly after a Timing belt job..

Have him look again with this info!

 

[gatormark91]

New here but have been reading the posts for my 2000 Lx470, thanks for the past help.

I noticed my pulley tensioner was rattling so I replaced the pulley thinking it was out of balance. It seemed fine, so I went to the store and on the way back, the car dies, I coast into a gas station and pop the hood. The belt had jumped off the crankshaft pulley and pushed it back toward the engine. The belt is now on the Harmonic Stabilizer. Instead of replacing the pulley myself I called my local guy to tow it into his shop and repair it. He installed a new pulley, and the car would not start. He replaced the spark plugs and it would not start. Then he tells me that plastic from the pulley braking got into the timing belt housing and made it jump 6 teeth. His final diagnosis was bent valves.

So, I performed a compression test and all of the cylinders came up with 88 to 90 PSI. Is this possible? I know the readings are low but is there another reason for all of them to be this low and consistently the same PSI?

What @2001LC said... Take it to another mechanic, the one you are using does NOT know what he is doing.

 

[MikeC218]

Thank you for the reply and for confirming my timing belt suspicion. You are right the compression test was done on a cold engine because it can't get it to start, but your comment that the valves are ok is good news. He did replace the crank sensor, so I will look at the wiring for both and maybe replace the cam sensor.

 

[flintknapper]

Thank you for the reply and for confirming my timing belt suspicion. You are right the compression test was done on a cold engine because it can't get it to start, but your comment that the valves are ok is good news. He did replace the crank sensor, so I will look at the wiring for both and maybe replace the cam sensor.

Just replaced my cam position sensor recently because whoever replaced the timing belt last...did NOT put the wire back in the clip and was rubbed in two by the serpentine belt. So...take a look at yours. A belt breaking or coming off a pulley could easily take out the CPS because of it's location.

 

[gatormark91]

Just replaced my cam position sensor recently because whoever replaced the timing belt last...did NOT put the wire back in the clip and was rubbed in two by the serpentine belt. So...take a look at yours. A belt breaking or coming off a pulley could easily take out the CPS because of it's location.

.... and - those clips just break as a pretty normal occurrence, too. Heat and age. My wiring in that area is all held in place with zip ties, because they just disintegrated when I did my timing belt.

 

[MikeC218]

I found the new crankshaft sensor they installed but cannot locate the camshaft sensor any help would be appreciated.

 

[khymel5]

I found the new crankshaft sensor they installed but cannot locate the camshaft sensor any help would be appreciated.

 

[flintknapper]

I found the new crankshaft sensor they installed but cannot locate the camshaft sensor any help would be appreciated.

Drivers side...a bit above your A/C compressor. You can't see the sensor itself because it is behind the timing belt cover, but you can see the wiring harness and connector. The wiring goes through a round grommet in the cover. See the diagram @khymel5 provided above.

 

[MikeC218]

Thank you, gentlemen, appreciate the help.

 

[MikeC218]

Found the Camshaft Position Sensor, tested the battery side of the connection, it was good. Checked the sensor side of it and no continuity, so I changed it, and upon inspection of the old one, it had a dent on the top of the cylinder. I replaced it, and the car still does not start. There is a spark to the plugs, I have checked all the fuses they are good, I am now beginning to test the relays and there plug connection. Anything else to consider to get the truck on the road again

 

[2001LC]

Can you post a pictures of the plastic timing cover that pushed in or broke?

Few thoughts:

1. The time belt guide (AKA crankshaft position sensor plate) behind the harmonic balance was bent. It's what the crank sensor reads. By the dent on sensors this is very likely. You may be able to see this guide with a mirror, looking through crank sensor's hole.
2. Timing belt jumped some teeth when plastic pushed into it. You'd need to pull top covers so both timing marks of cams can be seen.
3. The wire or wire housing block connecting to the crank sensor is damaged.

One or more seem very likely looking at your crank sensor. If you find 1 or/and 2 to be the case, just do a timing belt job. R&R any damaged parts as you do.

It's not likely even if belt jump a few teeth that you bent valves. I say this because we've so may documented cases in mud of a jump or busted belt under load at high RPMs (HWY passing). None bent a valve. Toyota does state this is and interference engine, which means valve contact with pistons. But in real world, we just don't see it. We've had times that it was stated; "engine blew". But fact is, never in mud has there been any proof of this that I've seen. Proof like pictures from cylinder being scoped showing bent valve or damaged piston top. We've seen many times where new belt installed after a break, and all was back to normal.

This is not the case with the VVT engine in the 06-07. I've heard where shop tech at Toyota Dealership used wrong timing marks, the T's. The engine interfered and new engine was needed at out of shops pocket. They would make very sure, not just assume, the valves hit.

The "T" is just there to confuse us. "T" is not timing mark! Yellow arrow points to timing mark.

2 (a) sensor plate goes cup side out.

 

[MikeC218]

What if time belt guide (AKA crankshaft position sensor plate) behind the harmonic balance is bent do I have to replace it, or can it be repaired?

 

[2001LC]

I'd just replace it. I've some used ones. New is likely not much $. You'll be deep into the timing belt job just to get at it. So I'd just do a timing belt job while in there..

First is to look with a mirror and see if plate damaged!
Second is to see if timing belt jumped (check valve timing)!
Third is to scope the cylinders through spark plug holes, just to make sure no valve to piston contract!

 

[MikeC218]

Hi all back with some news, questions, and pics.
Installed a new cam sensor, buttoned it back up and it cranked but no start. Someone mentioned to check the timing, read up on it, watched a couple of videos, and used 2001LC's illustrations (thank you very much) for reference. Got the timing belt covers off turned the crankshaft until the cams where TDC then looked to the harmonic balancer's timing maker to see if it was TDC. There is no timing mark on the harmonic balancer, have you ever heard of such a thing? Kind of usless without one, so I noticed in the illustrations that there is a timing mark on the crankshaft behind the crankshaft position sensor plate. Pic #1, I am not sure what I am looking for but should the yellow mark line up with what appears to be a center marker on the engine. BTW when I pulled the harmonic balancer off it slid off, I am not even sure if it was even engaged with the key. Anyway, pulled the cam sensor and the crankshaft sensor to make sure they were OK, I will check their electrical connections tomorrow. Thanks for the input.

 

[MikeC218]

I just received the harmonic balancer with a timing mark and if I line up the crankshaft key to the harmonic balancer opening it would be way out of time according to the mark on the lower cover and harmonic balancer. Is there a mark on the crankshaft by the timing belt to move the camshaft and crankshaft in time. Also here are pics of the lower timing belt cover that broke.

 

[gatormark91]

Timing Belt at TDC or 50 Degrees?

I have been reading threads all over the place and keep finding different things for different years and I have seen people doing different things on the same model years! Please help, I'm not sure what to do next. (Everything has been fairly smooth to this point, knock on wood!) 1998 Land...

forum.ih8mud.com

 

[2001LC]

No that is not the marks you want for this timing test. Vacuum and clean the area.

The mark you've in yellow on sprocket is used when installing a new belt. New belt has marks that line up, only when first installed. Once crank turn (CW only) with new belt set to those marks, the marks on belt no longer line up. One time line-up just to set belt to sprockets.

The marks you need for this test:
The crankshaft key is the TDC mark. Also see we've a mark (cut out "V") on the sprocket that lines up with crankshaft key. The timing mark on engine's oil cover, is just a little bump (circled). In this illustration the crank need turning CW about 20 to 30 degrees before at TDC.

Again do not use the "T" on for camshaft lineup.

 

[MikeC218]

Thanks LC, so in the first pic the crankshaft is at TDC, but in the cam pulley pics they are off eight teeth. Do I remove the old belt and turn the cam pulleys to line up TDC before installing the new belt?

 

[2001LC]

Yes you can just pull off belt and turn the cams. This is best done with spark plugs out. Otherwise you'll fight compression as you turn crank or cams. You'll still fight valve spring tension on cam lobes. But with plugs out you'll get much better fell and it's so much easier.

If it was me, I just do the complet timing belt job now. That is water pump, both pulleys and tensioner. You can have at your door tomorrow with Amazon prime for under $200. Any oil in back of fan bracket at bearing seal or if it has any play, replace it as well. Additionally the drive belt tensioner should have a very could spring back. That is when you turn with socket wrench to take off pressure drive belt to remove or install drive belt, it should have strong resistance. If not replace it now.