ekupp

Looking for some help with a timing belt problem. I've owned the truck for about 2 years, it's a 1993 4Runner 3VZE, and I replaced the timing belt, both pulleys, tensioner spring, and water pump in September 2014. Since then I've put about 8000 km on the truck. I used a gates Timing Belt Kit from Rock Auto, but instead of going with a Gates water pump I decided to go OEM and got the Aisin one.

Fast forward to 3 weeks ago and I'm driving along under normal conditions, about 50 km/h, and the truck starts to shudder, loses power, basically acts like it's running out of fuel, then dies. I get out, and there is a small puddle (maybe about 2 cups) of coolant under the truck where I managed to pull to the side of the road.

I get it towed back to my driveway, and start testing to see why it won't start - fuel is fine, spark is fine, then I find it it has zero compression on all 3 cylinders on the right side of the engine. Pull off the timing cover, and it appears as if my timing belt has jumped about 10 teeth and somehow some coolant has gotten on it, I can see the spray off the timing belt on the rear timing cover. I then pull off the timing belt and find the water pump pulley bearing is toast. Feels like I'm using a pepper grinder when I turn it.

What could have caused this? 10 teeth seems like a hell of a lot for a timing belt to jump. Did the jumping timing belt break the water pump, or did the increased friction from the water pump cause the timing belt to jump? Or is there another factor that caused both to malfunction? Both idler pulleys are in good shape, and spin smoothly.

I'd appreciate any help on this, I don't want to put it all back together and have it just happen all over again.

scope103

Your water pump froze solid, and tried desperately to stop the timing belt. In the process, the cam sprocket kept turning for about 10 teeth, and eventually worked the water pump "free" to the pepper grinding state.

I can't tell you why the water pump failed (there isn't much to it), but I would definitely check for debris in the coolant.

While I would check that the cams turn well enough to work the valves, I suspect all you need is a new water pump and cooling system flush.

thook

This reminds of the time I did a valve adjustment on a 3vze for a buddy that owns a shop. He was short handed, they didn't really work on foreign autos anyway, and I needed the money. Anyhow, they'd also had me put in a new complete timing kit with a new water pump. Once I finished, it ran great like any engine should. But, a few days later, I had to go to his shop for some reason....I forget...and the darn thing was back in his shop half torn apart, again. I asked him WTF was going on and he said,"Oh man.....you bleeped this up bad!". Of course, he was playing a joke on me and nothing was due to error on my part. Turns out, though, the Gates #1 tensioner pulley blew up! Literally! It was in pieces! They use Gates parts all the time and had never seen that happen. So, just saying apparently sometimes there are lemons. Perhaps even with Aisin? Was it brand new or reman'd?

ekupp

Brand new water pump. Rock Auto is sending me a replacement now, so hopefully I should have the thing back up and running when it gets here in a week.

Without taking the valve cover off, I turned the cams and they seem to operate normally - tension, release, tension, release, etc... I'm hesitant to get into the top end because I'm kind of pressed for time.

Is it possible that the timing belt got damaged when it skipped? I checked it over and it looks fine, but that's probably a lot of stress that it doesn't normally go through.

millball

Don't reuse the timing belt.

Just asking for more trouble.

scope103

Timing belts are incredibly effective at what they do. If you pulled on one so hard that a cam sprocket actually "skipped," I can't imagine that the belt survived. No matter what it looks like.

Timing belts aren't expensive; the tricky part of the whole operation is getting the crank bolt out. Do a search here; there is a lot of discussion on good (and absolutely terrible) ways to do that.