V belts m20 2.5

[NMcC]

I’m going about replacing the timing belt on my 325i sport and I thought I may aswell replace the v belts and water pump when I have it stripped back but I’m ordering the parts online and was wondering if all m20 2.5 belts are the same as it has options of 125kw / 170hp or 126kw / 171hp?

It will be my first time doing a timing belt so all eyes will be ok the wiki hopefully it all pans out ok,

Any other bits I should have handy when doing it?

Cheers

[Cloggy Saint]

I'm pretty sure all M20 engined cars use the same timing belt but am prepared to be proved wrong! It would be wise to replace the cam belt tensioner at the same time for peace of mind.

[Brianmoooore]

Early M20 engines did use a different timing belt, with a square edged tooth, and one less of them, but I think very few, if any, of these made it into E30s.
Unless you know it to have been replaced recently, it's a good idea to change the water pump while the timing belt is off, since the timing belt tensioner spring locates against the pump, and makes it very difficult to fit the pump and its gasket, while keeping the spring in place.
There was a problem with some M20 tensioners, where the joint between the pulleys shaft and its mounting plate becomes loose, throwing the belt against the front cover and wearing it away. I once took of the timing cover on a M20 to find a belt about one third of the width that it should be.
The suspect tensioners are supposed to be marked Z231 (or Z321 or Z132) - can't remember the order of the digits.
For mail order, try Autoodoc.co.uk, who, in spite of their .uk URL, are based in Germany. Good service, good range of makes, and they tend to send exactly what you ordered, (unlike some other UK parts suppliers), with the option of free returns if the wrong part is supplied for whatever reason.

[steve_k]

the early m20 timing belt had 128 teeth (i had an early m20 that had one fitted & still keep a 128 tooth belt in stock) with slightly square teeth.

the proper/new/correct one has 127 teeth with more rounded teeth, also the correct tensioner is marked "Z127" on the back of it,

also there is a little trick when replacing the tensioner spring, compress it as much as you can then use either two very thin (3mm/4mm) cable ties or some strong wire to keep the spring compressed while you put the bolt/pin from it in place then cut the cable ties/wire & pull it out with some needle nose pliers,

[steve_k]

forgot to add,

if you can, replace the spring for the tensioner at the same time, IIRC bmw still supply them.

[paultv]

Personally I would replace the camshaft seal whilst it's all opened up.

And +1 for auto doc

Paul

[NMcC]

Thanks men , was planning to change the water pump aswell along with the the accessorie belts.

13 years since the timing belt and water pump was done even tho it’s only done 12k in that time but it could have perished over time so getting all this done right before it’s put on the road for the summer all being well

Any answers regarding the 125kw or 126kw just curious?

[Brianmoooore]

Any answers regarding the 125kw or 126kw just curious?

This is probably the '87 - '88 changeover from high compression ratio, primitive engine management to low compression, more advanced management. No change to cam belt and related bits.

[NMcC]

Is a torque wrench needed for assembly again?

[Cloggy Saint]

There are recommended torque values for the water pump etc but if you don't have one then common sense should be enough! Just don't over-tighten ...

[Brianmoooore]

'Ordinary' 8.8 grade bolts and nuts, doing 'ordinary' jobs are always tightened to the same specific torque,depending on their diameter. This is 22 Nm for M8 and 10 Nm for M6. As far as I can remember, all the fasteners that are involved in the jobs you are proposing are 'ordinary', but check with a workshop manual, such as Haynes 1948.
The length of an 'ordinary' combination spanner is chosen so that it applies the correct torque to the nut or bolt when 'comfortable' force is applied to it. Knowing the feel of that 'comfortable' force is something learnt by experience, but it's NOT do it as tight as you can get it, then a little more to be safe! Far more damage is done to mechanical assemblies by fasteners that are too tight that is done by fasteners that are not tight enough.

[NMcC]

Spent a couple of hours tonight futtering at it, down to the timing belt now trying to get the TDC markings lined up but was wondering what way to turn the engine to get them lined up, if I’m looking at the engine face on from the front of the car does it turn clockwise or counterclockwise? And does it matter if it turns in the opposite direction say 90degree if need be or would it cause damage even when timing belt is still on?

[steve_k]

it turns clockwise as you look at the front of the engine, may take a couple of full turns to get both marks lined up,

as for turning it 90dg the opposite way? i'd be very carefull.

[NMcC]

Any ideas on where I would get the guide pin and spring for the tensioner? Previous owner had the water pump replaced and left it out

[steve_k]

Any ideas on where I would get the guide pin and spring for the tensioner? Previous owner had the water pump replaced and left it out

i'd say main dealer, try cotswolds on here,

makes me wonder why the PO left it out?

[Brianmoooore]

makes me wonder why the PO left it out?

'Cause it's difficult to bolt the pump in place and keep the gasket where it should be when you're trying to hold the spring compressed. Many a gasket has been destroyed while trying.
Spring and pin don't do anything once the tensioner is fully bolted in place, so they're often left out, leaving the problem to the next person that changes the cam belt.