Turbojohn

I have about 15 in my 1998 ls 400. I replaced starter/water pump timing belt about 20k ago. The water pump froze and it snapped the timing belt at a very low speed...no more than 1500 rpm.

Has anybody had any luck with the timing change replacement without seeing any damage to the engine?

Its a VVT engine and we know what means: interference !

I know lots have been here and done that......this is avery nice LS 400 I hate to sell it for salvage but might have to. Not a scatch in the car.........new leather/tires etc with 136k on the clock 2nd owner

thanks

dicer

About 15 what? K $$$$$?
Salvage would be not very logical then would it?
1500 rpms no more than...............
You can damage valves by turning an engine by hand.
Engines are fairly inexpensive, engines and transmisssions are the easy stuff, now if the body or paint was a mess then yeah trash the car. No one well not many can reproduce the factory paint and body work, and the cost to do so would be in the 20k plus region, an import engine can be had for in the 1k area.
Depending on the damage your original could be fixed but if its other than just bent valves then its likely not worth it, way less to get a replacement. Changing the engine takes less know how than the timing belt replacement, though you would want to replace all that on a replacement engine.

aptoslexus

You mean a timing belt breaking without damaging the engine? Leakdown test.

bradland

I drove my '91 long enough I did the timing belt twice, and I just did my '99 (V V T) a few months ago. All 3 done with no issue after...

djamps

If you can do the TB yourself go for it and see. Otherwise it might make sense to spend a little more and get a used motor rather than spend twice.

aptoslexus

Wouldn't it be a lot less work to just set the pistons down in the cylinders and close the valves by turning the cams to do a leakdown test?

djamps

If it were me I'd be extremely nervous rotating the engine with the cam not timed correctly (u can't get all 4 pistons down at once), unless u really know what your doing it could cause even more damage.

aptoslexus

You can get all 4 pistons down at once. The procedure for setting the timing involves doing just that--moving the pistons down in the cylinders so that you can rotate the cams without hitting a valve. Of course care must be taken but one way or another you're going to have to move the pistons and valves that are now not in time.

djamps

thanks for clarifying. makes sense.

Turbojohn

Thanks guys.......I am thinking the engine is trash. This is a very pristine LS400 and its like a new car to me. The water pump froze I am sure and after I heard the bearing noise and saw the temps rise I knew what was going on. I had no place to pull over in traffic and just as I was going to pull over the timing belt broke. I would say around 1500 rpm or so. I am not sure how to go about buying an engine and the timing belt still needs to be changed....but most say the engine is trashed.

dicer

All the talk about a leak down test. Yeah that can be done as long as the cams are timed to the crankshaft.
If you do some haphazard thing, what could happen is the air pressure forces a piston down and another up into an open valve, then you have not helped a thing. So to do it a new T belt would need to be installed first.
A better option would be an inspection camera.
And you can use it to look in the rear end through the plug hole, under the dash and behind door panels to see how the clips are attached etc. Very handi items. Also through the transmission drain hole looking for debris or what ever.

aptoslexus

I really don't think pressurized air gives a damn whether the cams are timed or not. With the valves closed, the air is going to leak or not regardless. Yes, it would be a great deal easier to do with the cams timed, but you can do it anyway. If you're worried about the pistons moving, lock down the crank.

Leak down test on Civic with a broken timing belt:

dicer

The air is not the problem, it is how the pressure reacts against the piston. On a noninterference engine yes you could do it. And on something simple like a 4 cylinder like in the video. I say instead of us just talking about it, why don't you see what happens if you have an interference 1UZFE remove the T belt and show us in a video how its done.

aptoslexus

You're not making any sense at all. Like I said before, if you're worried about moving the pistons, lock down the crank. If you notice in the video, the air doesn't move anything. All the pistons hit valves in the video. That's interference in my opinion. Yes, it's a simpler engine. Yes, it's more work to do it in a Lexus V8. Doesn't mean it can't be done. That said, it's probably moot. If the engine was running, the damage is done.

Turbojohn

I have decided to replace the belt even though the vvt was running when it broke.......only way to really know