My cam belt has started to go very slack when cold and very tight when hot. I have checked to see if any pulleys are loose but they are fine. My other cossie is fine and never changes, hot or cold. Has anyone had this happen?

 

quite normal really, as the head expands as she warms up the belt will get tighter,

its just a case of checking it when its hot, or the belt may be to tight and break or suffer premature failure

 

What type of pulleys are you using?

 

Just regular pulleys

 

What type of cam belt is it?

 

NO way on earth is the head going to expand enough to take the belt from very slack to very tight, I seriously doubt you'd even be able to measure a difference.

tabetha

 

agree
change the belt and pulls for good ones

 

Are they ally pulleys ?

 

Exactly what i just thought when i read that!!!

Check that the tensioner is in good nick etc..


cheers danny

 

is the engine always at TDC when checking?

 

It is a genuine Ford one as a matter of fact I got it straight from Cosworth USA in California.

 

IIRC the long part of the belt should be able to turn 90 degrees if fitted correct

TAB maybe you should make a thread about fitting a timing belt on a YB

As you know your onions on the engines

 

I know how to adjust the belt, that isn't the problem, may be I haven't explained myself well enough. If I adjust the belt when it is hot to the correct tension, then check it again when it's cold I have one and a half inches of slack at the longest point, so much so there is a flapping noise when I run the engine which is the belt hitting the thermostat housing under the cam pulley and it is wearing a groove on the back of the belt. NOT the indentation that occurs in the middle of the belt from the contact with the tensioner

 

No just normal Cosworth ones

 

No I have tried both TDC and other

 

Pics would help a lot via language help

Can you get any

 

Hey captiva.
Check that the timing belt tensioner is tensioned clockwise before tightening the nut. It sounds like its tensioned the wrong way (ie) anti clockwise. I have seen this done before, it allows the belt to be in contact with the thermostat housing enough to cause damage.
Clockwise Allows the belt to be lifted away from the thermostat housing by the tensioner.
Let me know if this helps.

Regards, Stephen.

 

Captiva. Hope This helps you.



Regards, Stephen.

 

It is running as you say so it is correct, what I was trying to explain earlier was that the tension was so slack it was allowing the cambelt to flutter along the top flange of the thermostat housing, it actually does hit it and causes some wear on the back of the belt but thank you for your suggestion.

 

have you tried taking the belt back off and retiming it all back up again.

 

All manually adjusted belts should be checked for tension when the engine is hot, this is the reason manufacturuers have now turned to self adjusting belt tensioners, so the tension is linear and always correct nomatter what temp its at.

the belt may not actually be that slack when its cold, but when they run they often appear slack because of the slap effect on the longest side of the belt.

i see alot of belts fitted by other people here, and some even whine when they are hot, as they were tensioned up when cold.

 

It would expand more than you think

We collected a friends car from a very well known tuner and my friend said not being cheeky but is that timing belt not too loose.

He said it will tighten up when its warm, we stopped after driving for a while and it was tight.

 

+1

 

well i for one didnt know that and am not afraid to admit it.
i guess you just never stop learning about the cosworth.

 

My problem is that while it is cold it is flapping and hitting the T/stat housing and wearing the belt. Remember it gets down to -42C here in a couple of months time.

 

No I haven't but where are you going with that? I will be fitting one shortly as this belt is gonna break!!

 

I wondered why mine whines when it gets hot as ive tensioned it when it was cold , learn something new every day .

 

Yes its very true but still wont give 1.5 inch of slack!!!!
This guy has a problem and it wouldnt matter a fuck if it was timed hot or cold!!!!lol


cheers danny

 

Its quite a common problem guys, I have never heard a good enough reason to believe why some blocks expand more than others although I suspect that oil/coolant temperature variations between engines and previous overheating will be an issue if its ever examined carefully, but the fact is this is a known problem, we used to have them brought to us at Ford when brand new with noisy cambelt / cover interference.

Tensioning them backwards causes a seperate problem, but its a problem all the same, I suspect in this particular case that one of your cars is tensioned backwards causing the stat housing interference you mention.

Regardless: Tension the belt when fully hot using a strain gauge and pull it to teh right hand side oof specification. remember, this chap isnt in the UK, when he says cold he desnt necessarily mean its only 10Deg C. LOL

 

According to some experts on here you are imagining it mate...

 

I definitely have both tensioners on both cars tensioned in a clockwise rotation and the reason it hits the housing is the "flapping" motion of the slack belt not because the belt is routed differently i.e. if it were tensioned anticlockwise. It's not cold yet we are at +6C but Christmas will be -20C and January will be in -40C, February HELL freezes over!!

 

Stu, is it only cossies that suffer this problem or do other engines suffer? sounds like pottentially all engines can suffer.

i've done my cambelt on my 2l zetec an tensioned it when cold and never had any problems when cold or hot with it.

 

Quite a lot of engines suffer from it, the severity depends on the material the engine is buit from and the natural elasticity of the belt.

 

interesting stuff stu

cheers