Hello all, I need some insight here. One of my T4R is doing something mysterious. It is a 99 3.4L with 184K miles. When I bought it, the timing belt had snapped. I changed the timing belt, WP and the pulleys. After 4 days, the vehicle wouldn't start. Just kept winding. After doing all the preliminary checks, I found out it was off timing. After taking the whole thing apart, I found out my timing belt had stripped (see picture). So I changed the timing belt again with a new Aisin hydraulic tensioner. I put it all back together and everything was hunkie durie for a few day until today after work, it did not want to start. It finally did but it wasn't "purring." I got home and checked the timing and lo and behold, it had jumped THREE TEETH. Now I am stumped. Any ideas here. This is not the 1st T4R that I have changed the timing belt. I have a few of them. Any insight here would be appreciated.

 

Did you turn all the idlers and water pump by hand and feel for roughness, or play??

Could be a bad bearing that locks up periodicly. Even new stuff sometimes fails.

 

Thanks millball, I am going to do that when I take it all apart tomorrow. It's really frustrating

 

Unfortunately, if it's stripping teeth off the belt, it means that one (or both) of the cam drives is encountering some excessive drag. The tensioner, idler, and waterpump all run on the back side of the belt and don't stress the belt in the same way. If they lock up or drag too much, they're just going to start squealing against the belt instead of stripping teeth.

With the belt off, try putting a wrench on the cams and turning them around. They will have a fair amount of resistance as they open and close valves, but it should move smoothly between valve openings.

 

You are right Jomoka. I actually did that already and the cams have more than usual resistance especially the driver's side. What could cause the cams to have excessive resistance?

 

The cams have a bunch of bearings. And a gear drive. And a bunch of cam followers.



If the head hasn't been getting adequate oiling it could be pretty ugly in there.

Pop the valve cover off and eyeball the lobes and followers/lifters. Maybe take off a bearing cap or two and check for galling.

 

Wow that's a clean head, that's got to be a new or reman. It's not indicitive of what OP is going to find when he pop the valve cover.

 

 

Think of the children, man!

 

Maybe they reached for the wrong jug and filled with maple syrup instead of 5w30.

 

That doesn't look right to state the obvious. I haven't opened my valve covers yet since the timing belt has been stripped but I opened it when I did the valve cover gaskets and they actually looked great. They were relatively clean. Infact, I thought they couldn't be cleaner compared to my other 4Runner. I haven't had the time to take it apart and probably won't have the time for a while. I do have a part motor that has a crack by the oil pressure switch. The engine ran great except for that. I guess I will be swapping the heads out. What do you guys think?