yosuthnmasa

1998 Civic EX 140,000mi.

Sorry for asking a question that I know has been answered. I've read through so many posts and believe I understand what I need to do but just want to get some clarification.

I'm in the process of replacing my wife's timing belt. I've got every replaced including timing belt, water pump, cam and crank shaft seal. The manual I have doesn't really explain how to set the tension on the timing belt. I don't want to put it all back together and have to take it all back apart just because the tension isn't right. I've read 3 thoughts on how to set the timing.

After turning the motor over 5-6 times to get the timing belt centered properly on the pulleys here are the 3 recommendations that I've read:

A) loosen the timing belt tensioner pulley bolt, push on the pulley until it is tight while re-tightening the timing belt tensioner bolt. Crank the car, if it whines its too tight. Repeat the process, but not as tight. Repeat until belt doesn't whine.

B) loosen (2/3 to 1 turn) and then tighten the timing belt tensioner pulley bolt after the belt has been centered properly. The spring pulling on the timing belt tensioner pulley will automatically set the tension when its loose. When you tighten the tensioner pulley bolt back down it will hold this tension.

C) while at TDC (Cam gear lined up head level and crank gear pulley mark lined up with lower timing belt cover notch) with timing belt on, rotate cam gear counter clock wise 3 teeth (by turning the crank bolt CCW which will cause the timing belt to turn cam gear CCW). After turning cam gear 3 teeth CCW, loosen timing belt tensioner pulley and then re-tighten the timing belt tensioner pulley. When the bolt is loosened, this will allow the slack in the belt to be taken up by the tensioner pulley (via the spring which will adjust the pulley). Retighten the tensioner pulley bolt to maintain this tension.

Your help would be greatly appreciated on this. I've asked in other places/forums but just couldn't get any answers.

jadziasman

You have the new timing belt on already? My reply may be too late for you but here goes anyway.

D) none of the above. C was the closest answer. To adjust the tension you must first loosen the tensioner bolt by 180° when the cam is at TDC. Then you rotate the engine CCW for three cam teeth. Then you tighten the tensioner bolt while you are holding tension on the belt with your wrench on the crank pulley bolt. Then rotate the engine several revolutions to make sure that the TDC mark on the cam corresponds with the TDC mark on the crankshaft to make sure you didn't put the belt on incorrectly - read on.

As long as the timing belt stays on the tensioner and is correctly installed, the belt will move the cam by the exactly the same amount (the cam moves two revolutions for every single revolution of the crank shaft) regardless if the belt is loose or tight on the tensioner side of a SOHC. It is critical that the belt is tight on the front side of the engine where the cam and crank pulleys are directly connected by the timing belt. You wouldn't want to be one tooth off on this side - then you could never fully tension the belt and you could end up having a really bad day later if the belt slips off - yike!

The procedure is more tricky with a DOHC - hate them I do (I love Yoda speak).


Modified by jadziasman at 10:07 PM 4/6/2008


Modified by jadziasman at 10:09 PM 4/6/2008

mechanix619

^^^He said it above but here is a picture. I'm a visual person.

yosuthnmasa

First off, thanks to both of you for the written and visual aids. Let me repeat back to you what you explained to ensure that I do it right (I do have the belt on already but haven't put everything back together). I have a couple of additional questions as well.

Make sure cam gear is at TDC. Loosen tensioner pulley 180 degrees. Rotate crankshaft (by turning crankshaft bolt) CCW until cam gear moves 3 teeth. Tighten tensioner pulley bolt to hold tension. Rotate crank until I can verify that I'm at TDC at the cam and crank pulleys.

Questions:
1) I assume when you say loosen tensioner pulley by 180deg., this is loosened from its factory torque specifications 180 degrees.

2) Why does the cam gear need to be at TDC when moving the cam gear 3 teeth? I understand that inevitably both the cam and crank gears need to be in the right place so that the timing is right, but does the position of the cam gear while pulling out the slack in the belt (towards the front of the engine) matter? Doing this is not a time or frustration issue, but I just wondered.

3) What is the best way to avoid installing the belt wrong (i.e. off by one tooth on the belt towards the front side of the engine)? Is there a best practice for installing the belt so this doesn't happen? Other than excess slack in the belt and the timing marks never lining up, are there any other indicators that I might be off by one tooth? How obvious will it be when aligning the cam gear with its marks against the top of the engine and the crank pulley mark with the notch in the timing cover? Will one of these be significantly off, or will it be close enough that you could misinterpret the alignment?

Thanks again for the direction. Please bare with me through the questions.

jadziasman

Unlike an ordinary drive belt, the timing belt has teeth so that the crank and cam pulleys are assured to move together when the crank pulley is turned without any risk of slipping. In fact, it is really difficult to get it wrong on an SOHC.

All you need to be sure of is that the left side of the timing belt which is at the front of the car and not the front of the engine is tight. It is obvious (to me anyway) when the belt is in the correct position on this side. Maybe when you're done you can count the number of belt teeth on its left side from the top of the cam pulley to the bottom of the crank pulley - next time I will!

Just take my word for it, you won't have any trouble with the belt being in the right place with the belt tight at the front side of the car. The timing will be right as long as the cam and crank pulleys were lined up right first.

The tensioner bolt is loosened by about 180° including break away torque. It can be loosened more without trouble but you just need it just loose enough to allow the tensioner pulley to travel along the elongated slot at its center on the shaft the pulley is mounted to on the engine block.


Modified by jadziasman at 8:37 PM 4/7/2008

19slocivic97

I think you've got some good information, the only thing that may make it a little easier is somthing that i learned a few years back and i still use it today. If your engine is in time when you take it apart( doesn't work for broken belt) take a sharpy and mark your timing belt at the cam and crank(draw a line on belt to gears) then remove old belt and transfer marks to new belt and install, this will make it alot easier for you to make sure that you put the new belt back in time. good luck

jadziasman

Excellent idea, 19. The timing belt doesn't stretch. So, marking it that way will assure that the new belt fits correctly.

yosuthnmasa

Thanks for the follow up. You answered most of my questions very clearly. One that wasn't answered was why does the cam need to be at TDC when taking the slack out of the belt? Maybe it will be answered in my description below of my experience.

I insured the cam was at TDC, loosened the bolt 180 degrees, moved the cam gear 3 teeth CCW. As I turned the crank bolt CCW it got harder and harder to move the the crank. I assume this is due to th piston moving up and down in the cylinder (perhaps easier to move the crank on the way up and the way down, but harder at the very top and very bottom of the cylinder).

My first go around was a dry run to make sure I did it correctly the second time. Just as I passed the third or so tooth, the amount of torque required to turn the crank slacked off. While moving it through the teeth moving process, it appeared that the tension in the belt (towards the front of the car) grew more and more tight as I reached the third tooth. In essence it was looser at TDC, but as I moved CCW it increased in tension. This process repeated itself (maybe 4 times for 4 pistons) as I cycled through turning it all the way around CCW back to TDC.

Likewise, my tensioner including spring would begin to stretch at the beginning of the process and continue to pull the belt tighter (or maybe the belt pushed on the tensioner pulley to cause the spring to push out) as I reached the 3 tooth mark. At this point, I retightened the tensioner pulley bolt to the proper spec's. I put the lower timing cover back on and lined up my crankshaft line with the notches and the marks on the cam gear with the head and they appear to be right, although it is quite difficult to really tell how in line the horizontal marks on the cam gear are when compared to the top of the head.

At this point, my only concern deals with the tension of the belt eventhough I followed the process to a "T". As you mentioned, you want to make sure the tensioner pulley is loose enough so it can travel up and down in the slot in the pulley while you move 3 teeth CCW. This allows you to remove the tension in the belt. If 180 deg. wasn't quite enough to loosen the pulley bolt, would this allow the whole tensioner pulley and spring to flex back and forth as I described? Or rather, should the tensioner pulley and spring flex back and forth as the engine is rotated when the tensioner pulley bolt is loose (due to the pulley moving in the slot)? Or, should this only be happening when the tensioner pulley bolt is tight?

Also, i pushed on the belt at TDC before I removed it to get an idea of how tight it should be. Now when I push on it at TDC it is quite a bit more tight than the original tension (and these belts don't supposedly stretch). After tightening the tensioner pulley bolt, is the tension of the belt a function of where you are in the cycle of the engine? Or should the belt's tension always remain constant? Maybe I'm having varying degrees of tightness in my belt because I resinserted my sparkplugs on anticipation of starting the engine. Should the sparkplugs be removed while setting the tension to keep the cylinders from getting pressurized and effecting the belt tension as I rotate the crank?

yosuthnmasa

19slocivic97, thanks for the advice. After reading this suggestion somewhere else before taking the belt off and not knowing why one would do that, I realized what a great idea it was after I removed by belt. Too late once I took it off. Guess you learn the hard way. I think i have the timing correct though.