Timing Belt Slack Explained [Merged 6-7] loose cam sag sagging sprockets gears

[defbear]

I was just wondering if its normal for the timing belt to have some slack after its been sitting over night. I have been checking it for the past few days. When the car has just been shut off and for a few hours after its nice and tight with virtually no play. But in the morning when I check it there is some, not alot, but some play. More than just after its been driven. The timing belt and tensioner were replaced about 2000 miles ago. Anyone have any ideas?

 

[steve]

Mine seems to do the same thing and I've taken off the cover and rechecked the tensioner. I'm guessing that over night the tensioner retracts from the tension on the belt and the valve springs cause the cams to move a little giving a little slack in the morning. Does it tighten right up when you run it a sec? Does it stay tight for a while after turning it off?

Steve

 

[defbear]

Yep. Mine does the same exact thing. I was actually going to change the tensioner because I was so worried about it. After I turned the crank to put the number 1 cylinder to TDC I rechecked the timing belt and the slack was gone!! So I too figured that over night the tensioner must retract just alittle or something to that effect. Thanks for the reply. Now I feel better :>)

 

[Dsmed]

yes this happens on just about every dohc motor due to the exhaust cam turning back a little bit to relieve tension, it goes to a more comfortable state. If it is a lot of slack, then I would retighten the tensioner, but if it is only a little, I wouldn't worry about it.

 

[mitsutuner]

replace the tensioner before the crank slips off a tooth on the belt and you have to replace bent valves. The tensioners should never be re-used and are sometimes defective when new. Sonny, the alpha mechanic at World Wite Auto in milpitas has a method of bench testing the tensioners before he installs them. t-belt tensioners and crashed motors are the lifeblood of the dsmtuners repair and maintenance forum, a lot of information here in previous threads. gregorio

 

[Dsmed]

I ended up replacing my tensioner 2 times before I found out that every DSM has the slack happen. I could walk down a line of dsms that have sat over night and pull the timing belt upper covers off and they will all have this slack. If you have enough slack to pull your t-belt off of the cam gears then yes you have a problem, but a little bit of play is normal when it comes to the 4g63 motor. The exhaust cam is the culprit of this happening.

 

[Tranman]

Yeah, I just had that problem. Was doing a 1G head conversion...put everything back together (thought tensioner was still good, only had 30k miles on it) and then after I let the engine sit for awhile, it had nearly a inch of play in between the cam gears....and could easily be yanked off. So I had to yank everything back off and put in a new one....very little deflection now....maybe a 1/4 inch or less.

 

[mitsutuner]

Remove the top T-belt cover and what do you see-- a lot of slack on the T-belt between the 2 valve cam sprockets. I almost shirt my pants when I saw this, so I took it to 1 of the ace mechanics at World Wide Auto in Milpitas to find out >
This is normal, as expalined to me--At the point in time when you turn off the ignition, 1 of the pistons will be in the compression phase, and this compression bounces the crank a little ccw, and slightly compressing the hydraulic T-belt tensioner in the process.
The intake sprocket also will turn a little ccw, but the exhaust sprocket will not, thanks to exhaust valve spring compression. The resulting cam sprockets turning towards each other and creates the slack on the belt.
Left to sit overnight, the hydraulic tensioner may or may not spring back out enough to take out the slack because of the exhaust valve springs pushing on the exhaust cam sprocket---it depends on exactly where the motor stopped it's rotation when you turned it off, AND the compression forces coming from the hydraulic T-belt tensioner, (you DID put a new tensioner on when you replaced the T-belt, RIGHT?).
When you start the motor, the cw rotation of the crank allows the hydraulic tensioner to extend and take out the slack, hopefully before the motor fires and starts running--you DID put a NEW tensioner on when you replaced the T-belt , RIGHT!!

 

[RaysTsi]

i bought a 6 bolt longblock and had it shipped to me , Ive noticed that the timing belt on it doesn't feel as taunt on top in between the cam gears, compared to my 7 bolt.

 

[Ðawg]

Try replacing the tensioner. From what I understand, you shouldnt be able to move that bad boy with your hand, it should be so stiff...



--Scott

 

[scuRRed whiTey]

i second that guy up top too...u cant move those things with ur hands when there on right

if u cant slightly move it....and u start the engine...consider gettin a valve job and cylinder head job done...cause there gonna all be bent and cracked when u try to fire it up and that shit breaks

dont be stupid and try either way......just replace the tensioner

 

[Ðawg]

Yup


replacing the tensioner would be the easiest and less troublesome first step.

--Scott

 

[DSMRevolution]

The cam gears will "rest" after sitting for along time. The belt after about 6 hours or so (engine not ran) will have about 3/4" of play up and down in it. Nothing to worry about. As soon as you turn the engine over it should take up the play. But yes, the belt will go up and down a bit.

 

[RaysTsi]

Its been sitting for 2+ months but I can pull the belt up enough to almost get one of the teeth out of the groove on the cams. It feels good and taunt on the sides though.

 

[nh98gsx]

what should the timing belt deflection be between the 2 cam gears?
please help asap before i drive it anywhere and jump timing again.
currently it is at just under 1/2".

 

[Defiant]

The tensioner is what takes that up, and the cam sprocket isn't where jump usually occurs- it's on the drive at the crank. Have you ever turned a cam in a head, with the valve train in place? They don't just turn- as you fight the valves both opening and closing, and pressing on the leading and trailing ramps of the lobs, they're notchy as hell with a good bit of kickback. To check the belt tension, take off the covers, put the car in 5th and push it forward until you see both cams turning. Block it so the engine doesn't have a chance to kick back, and then check the tensioner.

 

[Turbo Monk3y]

Well me and a friend we both have 2g turbo AWDs and we pulled off our timing belt covers and noticed we have alot of play in our timing belt... its tight enough not to come off but still loose enough to make us worry. How do i fix this and Why is there play in our timing belt.? My brothers 1g timing belt is very tight so im kinda worried...

 

[Scrymerr]

Mine is the same way. I think its cause the auto tensioner just takes the tension off while the car is shut off. Im not worried about it.

 

[Turbo Monk3y]

yeah thats what i was thinking since both of our 2gs are like that then we also noticed another locals 2g eclipse does the same thing so im guessing your right.. i mean thats 3 cars + yours that say that have that problem so im feeling a little better i guess thanks for the reply

 

[project94tsi]

just as long its not twanging like a guitar string in between your cams when the engine is running then its fine.

 

[Blam]

my old one was pretty tight...i just had mine done and it is a bit looser, but still tight enough not to loose slack

 

[Stanford]

Check it right after you turn the car off. Mine was always tighter right after it was shut off as opposed to sitting for a few hours.

 

[Defiant]

Depending on where exactly the crank stops, you can wind up with the cams being forced toward each other (rotationally) by the valvetrain. This wll produce an alarming-looking amount of slack in the top of the belt between the cam gears, but it's taken up as the starter turns the crank. Yet another reason to keep the top cam cover on. There are some things you just don't want to see.

 

[Turbo Monk3y]

hahah yeah really i took the cam cover off and almost flipped

 

[tsidrift1]

i put a new timing belt on and i got the marks perfect and it runs great. the only problem is that it is loose. i tightened the tensioner pulley like i was supposed to and the auto tensioner had a lot of force when i was compressing it. it is real loose between the intake cam and the idler pulley. as it idle you can hear the belt. it is like the rubberband effect. you know when you hold a rubberband tight and then grab one side, pull it and let it go and it makes that sound. that is what my timing belt is doing. when i drive it, i can hear that noise until i get to about 3500 RPM's. i dont know what to do. the cam sprockets are not from a turbo engine. they are from a 2.0 NT. is that a possible answer.