RB25DET timing belt questions

[exodus5547097]

I have the bottom cover for the timing belt on, but I'm trying to remove it so I can remove the timing belt. How do I remove the bottom cover for the timing belt that sits on top of the crank pulley? How do I remove and install a timing belt? How do I reset the timing on the timing belt(what degrees)? A picture may help me.

[mello88]

To remove the lower timing cover you'll need to set the engine to TDC #1, then remove the crank pulley. To do this you need a 27mm socket, and a gear/pulley puller kit (free to borrow from autozone). You may need to lock the flywheel in place with a socket, to stop the crank from spinning as you remove the crank pulley bolt. If you use an impact gun it will make your life easier!

To put the timing belt on and set the timing & tension... Well, first off you absolutely need to download the FSM and read through that section. Now read it again to be sure.... Look in my signature for a download link.

OK after you've obtained and studied the FSM, the process goes something like this:

After the crank pulley is off, you can get the lower timing cover off. Remove the curved dust plate between the crank pulley and the lower timing belt gear. Now loosen the tensioner nut, holding the tensioner in place with an allen wrench. After that, rotate the allen wrench counterclockwise to set the tensioner at it's loosest position. Now the belt will slip off the cam gears and lower timing gear.

Install the new tensioner (loose for now) and guide (you bought these, right?) then align the timing marks on the new belt with the marks on the engine. There are two marks on the upper timing cover back plate (behind the cam gears) and there is one mark on the oil pump near behind and to the right of the lower timing gear.

Now put the crank pulley back on temporarily, and rotate the engine by hand a few times. This will settle the belt and automatically adjust the tensioner. After you've rotated the engine >=720 degrees, use your allen wrench to hold the tensioner in place as you torque the nut on the tensioner down... FSM has torque specs.

Now put everything back together, and be prepared to re-adjust your CAS so the engine can fire up.

My tips and other info that might be useful to someone doing this the 1st time:- The timing belt has a frontward pointing arrow. Pay attention to this when you reinstall it because if you put it on backwards the timing dots will not line up properly and you'll get frustrated real quick!

- Rotating the engine by hand is what adjusts the tension of the belt against the tensioner spring. This is providing you have a good spring still.

- Apparently you should have a ~45 degree deflection if you twist the timing belt, when it's set at the proper tension.

- If you put too much tension on the tensioner, the belt will be too tight and you'll be doing the job all over again, so do it right. Read the FSM and search around cause this has been covered quite a bit.

- Getting my new belt on the gears was a pain in the ***. I got it all lined up and put only the first few mm's of the edge of the belt onto the timing gears. Then I used a rubber mallet to gently tap the around the opposite edge of the belt to nudge it on the rest of the way...

- The curved washer behind the nut on the tensioner goes on a certain way. The concave face should face the block. Read the FSM!

- You should have marked your CAS before you removed it. But you probably didn't, so now you're going to have to adjust the CAS to reset the base ignition timing before you get the engine started again. Read the FSM!

It's been a while since I put my timing belt on so I may have left out something important or otherwise misinformed you so look it all up yourself to be sure.....

[Coolwhip]

I'll say it for you. Mello saved your life.

Good write Mello!

[l0nestar]

I second that Coolwhip!

mello88,Good job with the description!

This I will add - Make sure you have the FSM for the torque specs and how to set it. My 25 was on the stand when I went to install the new timing belt, and it was a pain in the arse to do it, but I got it. The most frustrating part (for me) was getting the belt actually on - Like mello88 said, get it a few mm on, all around and lightly tap it on. and be SURE to check the alignment marks on the belt, they ARE there for a reason -- the first time I got my belt on, I was checking it out and realized the exhaust cam was off a tooth / notch! So I had to pull it off the exhaust side and make sure it was on proper and carefully tap it back into place. But when I first fired my engine, it started on the first try and sounded beautiful!

I hope my mistakes help you! (Isn't that what this forum is for? - learning from others mistakes )

*edit* Oh yeah, and for myself, to crank the engine, I had a 27mm socket and a 1/2" breaker bar But it got the job done!

[FriedEGs]

yea, the belt is a pain in the azz to get over the cam gears.. just be patient and work with and you'll get it on eventually..

also, if you hook up the cas without the cam gear cover plate thing, the cas WILL rub against the cam gear, so either put the cover back on or use some thick washers to supplement the gap...

[radianation]

Sorry for the old thread, but found it on a google search and the writeup is very helpful. Question - What if you timing cover back plate is missing the timing marks?

[Coolwhip]

Crank key way should be pointing directly to 12 o'clock.

stock oem intake cam gear (rb25) will have it's timing dot point at 10 o'clock.as well the top most bolt end that hold the front of the gear on should be centered on the rocker cover.

exhaust cam gear timing dot should be pointing at 2 o'clock and the CAS key way (star shape with half a moon) should have the half a moon flat side up like a table top.

I'll get pics for ya.