Timing Belt too tight??

[S. Baker]

I know I can hear timing belt wine on my 94 MTX. I was wondering how the tension is set on the timing belt of a 3.0L engine? When I changed the timing belt I remember seeing a sping loaded tensioner. I followed the instructions from the FORD shop manual. Any ideas? I plan on tearing into that side of the engine in the near future and I wanted to reset the belt!

It was adjusted by the allen head screw, how does one know if it is too tight? Is there a certain torque?

<small>[ February 22, 2002, 03:15 PM: Message edited by: S. Baker ]</small>

 

[jthomas68]

The MTX`s have a manual adjusted tensioner.You turn the 5mm(?)allen head to set the tension,then tighten the pulley bolt to set it.The ATX`s have spring loaded tensioners.I`ve never heard of them being interchanged.Is it a possibility?

 

[sdpatt]

The 3.0L engine has a spring loaded tensioner and the 3.2L has a gas piston tensioner. There is abolutely no possibility of them being interchanged.

The procedure to set the tension on the 3.0L is to install the belt and release the 14mm locking nut on the tensioner pulley to apply the spring tension to the belt. The timing belt covers and damper are then reinstalled with the rectangular port on the middle timing cover removed for access to the 14mm tensioner locking nut.

The crankshaft is then rotated approximately two turns in the clockwise direction until the yellow mark (first) on the crank damper aligns with the "0" degree mark on the lower timing belt cover. This sets the number one cylinder at 60 degrees BTDC and causes the greatest slack on the tensioner side of the timing belt. The 14mm nut is then tightened to set the tension at the greatest that can be applied by the spring. It is normal to hear some whine after a new belt is installed until the belt teeth become familiar with the pulleys.

The 3.2L is even simpler. After the timing belt and tensioner are installed, just remove the pin that was installed in the gas piston to hold the piston in the compressed position. The gas piston does all the work.

<small>[ February 22, 2002, 10:34 PM: Message edited by: sdpatt ]</small>

 

[Shoman94]

sdpatt:
The 3.0L engine has a spring loaded tensioner and the 3.2L has a gas piston tensioner. There is abolutely no possibility of them being interchanged.

The procedure to set the tension on the 3.0L is to install the belt and release the 14mm locking nut on the tensioner pulley to apply the spring tension to the belt. The timing belt covers and damper are then reinstalled with the rectangular port on the middle timing cover removed for access to the 14mm tensioner locking nut.

The crankshaft is then rotated approximately two turns in the clockwise direction until the yellow mark (first) on the crank damper aligns with the "0" degree mark on the lower timing belt cover. This sets the number one cylinder at 60 degrees BTDC and causes the greatest slack on the tensioner side of the timing belt. The 14mm nut is then tightened to set the tension at the greatest that can be applied by the spring. It is normal to hear some whine after a new belt is installed until the belt teeth become familiar with the pulleys.

The 3.2L is even simpler. After the timing belt and tensioner are installed, just remove the pin that was installed in the gas piston to hold the piston in the compressed position. The gas piston does all the work.

Scott...Can you get a knock from the belt. I seem to have a knock at idle that is similar to knocking on plastic. I opened my oil fill and the noise did not increase. The noise though is greatest on the front bank at the place where the cam goes from the timing area into the head. Could that be the tensioner or something?

 

[sdpatt]

I'm very sorry to hear about that. It could be the timing belt slapping against the inside of the timing belt cover. Take off the upper timing belt cover and take a good look with the engine off and the engine running. There should be no visible up-down movement in the belt.

If you have a 3.0L, you can retension the belt by the procedure I mentioned in the earlier post. Take off the small door, loosen the 14mm nut, rotate the crankshaft to the yellow mark at the "0" degree index, retighten the 14mm nut and reinstall the door.

Scott

 

[Shoman94]

sdpatt:
I'm very sorry to hear about that. It could be the timing belt slapping against the inside of the timing belt cover. Take off the upper timing belt cover and take a good look with the engine off and the engine running. There should be no visible up-down movement in the belt.

If you have a 3.0L, you can retension the belt by the procedure I mentioned in the earlier post. Take off the small door, loosen the 14mm nut, rotate the crankshaft to the yellow mark at the "0" degree index, retighten the 14mm nut and reinstall the door.

Scott

I will look into that tomorrow. I hope that could be the problem. Its not majorly loud and it has done it for quite a while now without getting worse. What I did notice though is that it is worse when the engine it hot. I don't hear it when the engine is cold, Only at normal operating temp.

 

[sdpatt]

If you find slack in the belt when you have the upper timing belt cover off, also rotate the crankshaft and check that both camshaft index marks are aligned at the 12 o'clock lines when the crank damper is set to 0 degrees BTDC. Don't mind the lines on the timing belt - they will help only when installing the new belt.

Scott

 

[Catfishphillip]

When I removed the timing belt, I noticed the spring tensioner was merely tightened to the belt - the spring tension was never employed by the previous mechanic. The spring was disconnected and there was slack in the belt. I could find no instructions at the time on shotimes.com or in the haynes and chilton manuals, so I wound up the spring 180 degrees and kept the full tension of the spring holding the tensioner wheel to the belt. I put a second "buddy nut" on the stud to lock the two nuts together with just a tiny bit of end play on the tensioner. I believe this would allow the slack in the belt to always be taken up by the spring. It made more sense than setting a fixed tension and allowing the belt, which stretches over time, to develop slack in itself. I have changed other timing belts that employed 'constant spring tension' taking up the slack. Did I do wrong on the SHO?

 

[sdpatt]

You were on the right track, but the procedure for the 3.0L SHO engine says to turn the crankshaft damper two turns clockwise until the yellow mark is on the "0" degree timing mark (60 degrees BTDC). This lets the tensioner spring tension the belt when the slack side has the most slack. At this point, you are supposed to tighten the 14mm nut on the tensioner to set the tension. You can also pop off the little rectangular door in the middle timing cover periodically and reset the tension with the same procedure. I have done this ane hope to extend the change interval to 100,000 miles.

I'm afraid the the spring in the tensioner is not strong enough to keep the tension on the belt while it is at speed. You have opened a new door in the world of the 3.0L SHO's timing belt tension. Please let us know if there are any problems. You are the tester. Good luck.

Scott

 

[Catfishphillip]

Thanks for the reply, Scott. I've thought about it all day long today - if Yamaha designed the tensioner to be tightened down after adjustment, then it should be so... had I known about the little access cover two years ago, I would have adjusted the belt tension long ago. I can always remove the buddy nut and tighten down the one, single nut as specified. I've never seen a reference to the access cover in the lower timing cover on these internet forums!

Now that's a tip - adjust the timing belt tensioner occasionally, maybe annually or every 10K, to take up the slack and prevent bucking when accelerating.

That always bothered me when driving the car semi-hard, having the engine pull up rpm's and then around 4,000 rpm really take off, like the valve timing was inconsistent.

 

[sdpatt]

The engine changes tone at 4,000 rpm because the secondary intake runner butterflies have opened and the engine is now breathing through all 12 runners.

Scott

 

[Catfishphillip]

Yes, we're aware of that, but the apparently the timing belt slack trips up the exact valve timing through the rpm curve. My intake manifold gasket kit (black stuff on old ones flaked off, requiring replacement) and Bosch wires just arrived from Autozone - looks like I'll have the car back on the road this weekend. Thanks for the advice, Scott - nice to have a knowledgeable fellow owner with some experience on this forum.

 

[sdpatt]

Farther advice would have me say not to use those Bosch wires. Stick with the Motorcraft.

Scott

 

[Catfishphillip]

Nope. The Bosch wires arrived today. The only reason one burned was because of the damned oil in the well. Hey, I'm learning, like we all are - but I'm not shelling out ridiculous money on wires. Yes, I gather the main concern is fit - how the boots fit into the valve covers to keep dirt and stuff out. Homemade wires could do the job of delivering the spark, it's simple physics there, too! Forgive my immodesty, I defer to your wisdom, Scott! But the wires are in hand and, well, I'll update you on how well these Bosch wires hold up over time. I will be the test kitchen for these wires, howzzat! It's important to stick to specified parts on these specialized cars, and it's also important to think out of the box and stretch the imagination! That's how Ford and Yamaha came up with this performance car, instead of just cramming an old pushrod V8 in there. Like the tensioner idea I had, having constant spring pressure on the timing belt. Volkswagen Beetle spark plug wires would work, too! I could have reused the burned wire's boots and extension and just replaced the resistor wire for a few nickles... Again, I defer to your wisdom. I've only had this car three years coming up in June, and have done little engine work until now. It's challenging to work on and very dependable, we must agree! Thanks again, and best wishes... BTW I have a friend who likes in Richardson. Dallas is cool - I've spent a lot of time in Deep Ellum, West End and at the Fairmont Hotel. Not enough liquor stores around there! But wow, the restaurants, the Tex Mex! Best wishes...

 

[SHOBound]

I was reviewing this older thread and was wondering how often the MTX tensioners go bad on these ? Can you buy them if they do ? How much ? My motor has 100k on it, there is tons of slack in the belt and I'm 99.9% sure it jumped time.

 

[sdpatt]

The timing belt on the 3.0L SHO engine may become slack if the 14mm nut on the tensioner is not tightened or the belt has been installed way past its 60,000 mile lifetime. Even with a healthy spring in the tensioner, the nut must be torqued 25-36 lb-ft to maintain the set tension in the belt. The 3.0L engine's tensioner is locked in place by this nut and does not move to keep constant tension on the belt like the 3.2L's gas piston tensioner. Due to this older design, the 3.0L will allow the belt to become quite slack due to stretching if the belt has been installed too long.

The tensioner fails by the bearings in the pulley wearing. Unless this happened, there is no reason to replace the tensioner. A timing belt with 100,000 miles on it in a 3.0L SHO engine will allow as much as +- 1" of motion in the top span of the belt between the camshaft pulleys. If this was enough slack to allow the belt to jump a tooth, the belt is long overdue for replacement and has probably been damaged by the skip. Considering a new timing belt can be had for less than $40, parts cost is not the reason to avoid this required 60,000 mile maintenance for the 3.0L SHO.

If the belt has been on the engine less than its normal 60,000 mile lifetime, either the nut has come loose, the belt was not tightened adequately during the installation or the belt itself was weak and allowed excessive elongation. Only if you disassemble the front end of the engine and find the tensioner bearings damaged would you need a new tensioner. It is not nearly as common to find this than finding an old belt that has stretched beyond its usefulness. You must inspect your engine to see what services you need to do.

<small>[ March 01, 2004, 03:20 PM: Message edited by: sdpatt ]</small>

 

[SHOBound]

and I can tell if the bearing is bad by spinning the tensioner and if it grinds, its bad, right ? I still havent got into the motor, I just want to know what to look for so when I get into it, I am not running from the garage to the computer Thanks sdpat, you are a stud !

 

[sdpatt]

Certainly, if the tensioner does not rotate freely, the bearings are suspect. Grinding sounds or sensations would not be a desirable condition in any bearing.

A little grinding may be due to some debris in the bearing that has bypassed the seal. rubbing the bearing with a rag to clean the dust off can do this. The softer debris can be reduced to non-threatening size by the pressure and clearances in the bearing, but there will be some measure of life shortening.

 

[SHOBound]

So that is the only way the tensioner will need to be replaced is if the bearing is noisy, correct ?

 

[sdpatt]

sdpatt:
Only if you disassemble the front end of the engine and find the tensioner bearings damaged would you need a new tensioner.