Learn me: 4agze timing belt change

Never done anything like this before. What are some tips and things to avoid?

Before putting the cover back on pull the plugs out and turn the engine by hand a few turns and ensure the marks line back up and nothing is binding, it's fairly easy to end up a tooth slack on the taut side if the belt isn't marked. Do not bend the belt any tighter than the smallest pulley. Replace all the idler pulleys (bearing lifespan is roughly the same as the belt) and water pump if timing belt driven.

Or the easy way: Split the belt longitudinally, cut off the outer half leaving the inner half on, slip the new belt half way on the sprockets, cut off the last of the old belt, push the new belt the rest of the way on, put pulley, covers back on, have a beer.

Oh, tech tip: Put a breaker bar on the harmonic balancer bolt and against the floor or frame rail such that it won't move when the motor is cranked. Crank the motor. The bolt is now loose.

In reply to Dr. Hess:

I like this idea of cutting the belt. What do you recommend using?

For setting the tension whats a good gauge of tightness? Is a finger enough?

Dr. Hess wrote: Or the easy way: Split the belt longitudinally, cut off the outer half leaving the inner half on, slip the new belt half way on the sprockets, cut off the last of the old belt, push the new belt the rest of the way on, put pulley, covers back on, have a beer.

Thinking about this you could probably take the plugs out and then rotate the motor as you cut the belt with a razor knife. I am just wondering if only half a belt would be enough to overcome the resistance of the valve springs on the cam.

I do like this idea.

People do that half belt thing all the time. Yeah, plugs out, of course, and a half a belt is still plenty strong. And when you're done, of course, turn it over a bunch of times and make sure the marks all line up.

In reply to dean1484:

Hadnt thought of rotating the belt with the blade stationary. Good idea!

Time to sharpen up the old camping knife and get ready to tackle this job.

IIRC, the biggest issue with the motor in the car is removing the pulleys, covers and belt that sit in front of the timing belt. On the MR2, getting the motor support out of the way helped.

I seem to remember the 4AGE is like most Japanese motors of the time, it was oddly sensitive to getting everything back together in exactly the same way. Taking everything off without marking anything is therefore a really bad idea. (ask me how I know) Mark where everything lines up, where everything goes, and the position of everything in relation to everything else including the gear on the distributor if you pull that. The half belt idea is genius...I'd do that.

Also, the timing marks on the bottom pulley are unique to the car it came from. Just because the pulley fits and is the same size doesn't mean it came from a 4AGZE. You may want to confirm the marks are legit before you swap belts. Someone in the history of the engine may have swapped it out and that will cause you undue hours of frustration trying to get it to time properly. (Ask me how I know.)

This will be important if you swaps the oil pump, which is a good idea if the engine is out of the car.

It goes here:

Admittedly, if you half better luck than me and half a brain, you will avoid these issues.

In reply to pinchvalve:

The 4agze in question has been swapped in an ae86 and has a high boost pulley which I will be replacing.

hmmmmmmm.... NOT a fan of splitting the belt... means you are not changing the tensioner bearing that way.....????

As to the correct tension

So, based on these pictures, a 4agzebtpqx is some sort of a twincam 4? Easy peasy. Find the marks before you take it apart, follow the instructions, and make sure the marks are back where they belong afterwards.

I though we were talking about some V8 thing...which is exactly the same, only more.

I think the belt change interval on a 4AG is like 60K miles, right? and it is a non-interference motor. At least through the silvertop. I tend to swap tensioners, water pumps out like every other timing belt on setups like that.

It had a water pump done last summer before I bought it. The belt and associated tensioner need to be done. Looks like the fsm method is the best way then?

Yup, that's the way to do it. Line up the marks, take the old one off, put the new one on, rotate, check the marks.