Xu9J4 Timing Belt Tension

[Stuey 2]

Howdy guys,

 

I've just done the second belt job on my Mi16 and have found the belt seems a bit loose, but I know last time I had it too tight as it was whining a bit. So I expected to have it 'looser' this time.

 

The timing was spot on with the pins all perfect; the two cam pulley pins slipping in and out easily without binding. I had the 45 degree twist tension set up fine. But it whined like a supercharger, so I gradually backed off the exhaust side tensioner and retested trial and error until it stopped whining. The pins still go in, but the exhaust pulley pin is a tight fit.

 

But now it seems too loose. The two side belt runs feel OK, down near the pump and on the front run where you test tension, but the run between the cam pulleys can be pushed down about 20mm easily. The belt does sit flat across the pulleys though when you're not pushing down; it's just a little loose feeling to me. The car runs well and the 45 degree twist is still OK but is obviously a bit easier...like, it's not twisting 90 degrees or anything.

 

Can anyone comment on how tight it should feel? I'm aware toothed belts aren't like alternator belts...what do you think? This is doing my head in!

 

Cheers

 

Stuey

[2052NV 24]

i just make sure it does not flex far enough as to touch the plastic shroud on the long right hand side section. It is a nightmare timing up these engines with the stupid two tensioner rollers........ mine has vernier and that makes it doubly difficult!!

[Stuey 2]

If I push it hard enough it'll touch the RHS cover. But I'm still concerned about the tension. I have a gut feeling it's a little loose....that the top run should be firm but not tight.

 

I find the timing setup is quite good actually! I'm just not experienced enough with timing belts to know when the belt is just right, which I think is important on this setup with two solid tensioners. Once I've done it just right it'll be in the memory for good.

 

Any other comments welcome....

Edited August 21, 2014 by Stuey

[kyepan 291]

You can get in a muddle with these...and i'm about to give you a most unscientific explanation from my perspective, i've probably done cam belts on MI-16's about ten times.

 

 

Most importantly you have to get it roughly right then pull the pins out and spanner it round for two rotations and check the pins, then you know where you really are with the resting tension.

 

Generally you want about 45-70 degrees deflection on the longest run (front run). The cams will also find a resting point that may artificially tension one or other of the runs whilst giving slack elsewhere during the tensioning procedure.

 

Generally I wind on a max rear tension first to take up the rear pulley slack, then wind on a bit too much front tension, to pull the belt tight across the top between the pulleys,usually causing the pins to stick.. and then take off a bit of rear and a bit of front until it's tensioned across the top between the pulleys and then tensioned down the front and the pins sit okay.

 

granted, this is no scientific method, but the first time i did it, it whined...when re-tensioned it was too lose... so after that i just took my time until it was right, it takes time to do well but once you know what your looking and feeling for you can't really get it wrong.

 

Being anal here is a good thing, also not being satisfied until it's right is the second good thing, plenty of light, and the right tools to make tensioning in car easy are a good thing, dropping the engine down off the right hand mount helps immeasurably if you don't have tiny girls hands like me.

 

Cheers

Justin

[Stuey 2]

Hi Justin; you don't probably realise just how helpful that was. I had the impression that the belt between the pulleys is slacker than the rest and guessed it might have been what you said regarding the cams. I did essentially do what you said, by setting the front tensioner almost as tight as it would go, etc. etc. until I had it essentially right for both timing and tension. But that's where it was still whining. So your suggestion to persevere and the comment about the distribution of tensions is really useful.

 

Checking the tension at the various runs at crank positions other than the 'timing setting position' might also be helpful.

 

I do take the mount off and have made decent tools so that's all OK.

 

Thanks guys

 

Stuey

[kyepan 291]

glad to be of help, sounds like you've cracked it!

[Stuey 2]

Just a bit of an update. I couldn't stop the whine without the belt being loose enough for the front run to slap the front part of the plastic surround. This only happens at a very specific rpm, around 1500. Damned if I could solve it - either the belt's a little tight or it's loose enough to resonate at ~1500 and make a racket on the plastic.

 

I'm thinking of trying another belt brand, just to see if it'll make a difference. Dayco uses a slightly different profile they call CWC which they claim has 'soft meshing' with the pulleys. Or I might just put up with the whine, but it's probably not good for the bearings in the pump and tensioners.

[nixonmi16 5]

Hi I had the same problem on my alloy block mi16. I find the only way to get the tension correct is run the engine up to temp then readjust to 1/4 turn on belt . It amazing how much these engines expand and make sure the tensioner are turned the correct way other wise it puts the belt too tight round water pump as it changes the way it runs over the pulleys. I've done 3 belts on mine up to yet and never a problem doing it this way using contitec and gates belts

[Stuey 2]

Hi Nixon,

 

Thanks. The trouble is, it whines even when cold. If I adjusted mine to 1/4 turn (90 degrees) hot it'd really slap on the front of the cover. Have you had this issue? With the front of the cover still off, I can hear it while I'm driving, just as it goes through that rev range.

 

Pretty sure there are no worries with the way I have the tensioners; they're set up to tighten by turning anti-clockwise.

[yorkshirekowboy 19 1 Cars]

Sorry to hijack thread, I'm looking at doing my cam belt. Been looking at belt kits by gates as I know these are brilliant. My engine is an xu9j4 aswell (mi16x4) and cannot remember the amount of teeth on the belt. I'm sure it's 133 can anybody confirm this. Also is circoli water pumps a good brand? Regards Danny

[Anthony 1,003]

1.9 Mi16 is 133 teeth. Last Ciroli water pump I fitted worked but felt "cheap" - still going a couple of years later mind you.

[yorkshirekowboy 19 1 Cars]

Sweet thanks. What make would you recommend then? Regards Danny . Ps crazy amount of stuff I searched on this forum about cam belt info. I must be looking at the wrong threads haha ????

[yorkshirekowboy 19 1 Cars]

Are febi a good brand of water pump?