M40 Distributor area loud squeaking and squealing

Post Mon Jun 11, 2018 2:25 pm

Ever since I adjusted the timing on my engine, as it was 1 tooth off, there has been a squeak coming from the distributor cap area.

I initially thought it was one of the two timing belt pulleys squeaking. I have since replaced these and the noise is now even worse.

I have had the distributor cap off a few times and everything looks normal.

Definitely is not the water pump as I ran the car cold, without the accessory belts attached.

What in the distributor cap can squeak and squeal?

Post Mon Jun 11, 2018 2:47 pm

take the top cover off the cam belt. run engine mind pinkies and see if the cam belt is rubbing anywhere.
nothing in the dizzy i can think off, did you fit a new camshaft seal , which is behind the rotor arm. some folk do when replacing the cam belt ?

Post Mon Jun 11, 2018 2:49 pm

how did you re tension the cambelt ?

Post Mon Jun 11, 2018 3:14 pm

if the belt is over tightened it can howl ==== taken from haynes service manual 1948 .

Post Mon Jun 11, 2018 4:46 pm

Hi Arris,

Cam belt does not rub anywhere. Ran the engine on the starter motor with no sounds at all and with the timing belt exposed.

Have not changed the cam seal. Does not leak. Engine in general is in excellent nick. Only 60k miles.

I re-tensioned the cambelt to 30nm, with a torque wrench on with an allen key bit in the end. Haynes says 35nm. This seemed a lot to me when leaning on the end of the wrench and doing the obligatory thumb test on the belt for deflection.

I started the car and it squealed like a pig. I immediately thought it must be the tension on the belt, as you did and set it again, this time to about 22nm. This made no difference.

The sounds tend to go away over about 2000rpm to add to the confusion.

Post Mon Jun 11, 2018 4:58 pm

After a bit more reading from the Haynes it could be that I was mislead by the 35nm. That is if you have the BMW special deflection tool.

Going by the spring balance and allen key method described in the Haynes, 85mm long Allen key pulled by a spring balance with a force of 2kg =

0.085m * 20newtons = 1.7nm

1.7nm!! No where near 20nm or 30nm!

Will go adjust and see if this fixes it. Hope I haven't stretched the belt too much!

Post Mon Jun 11, 2018 5:42 pm

don,t know where you got 34 nm from but its wrong.

yes use an allen key about 100 mm long mark it at 85 mm this is where the s/b sits. pull it to 2kg or 4.4 lb
then lock the centre nut. turn the engine over thru 2 complete revolutions , loosen the centre nut and again use the s/b at 2 kg. tighten centre nut. turn the engine again 2 revolutions, check all timing is correct with top camlock tool and pin that goes in the crankshaft. then torque center nut on the belt tension adjuster and don,t forget to re- torque the camshaft top pulley bolt if you undid it.

Post Mon Jun 11, 2018 5:46 pm

in haynes manual bottom right picture ( 10.23b ) on page 2A.11

Post Mon Jun 11, 2018 6:05 pm

I miss read: Timing chain tensioner plug, as timing belt tensioner plug.
I then assumed that plug referred to the hole in the tensioner for an allen key.

Anyway. Thanks for your help Arris. Ran out of time today. Will finish adjusting tension tomorrow and report back.

Post Mon Jun 11, 2018 8:54 pm

oh yes easy mistake , timing chains only on the earlier engines , not m40 or m20. later e30 facelift

Post Tue Jun 12, 2018 8:15 pm

Found the spring balance in the garage after hunting around for a while.

Timing is now set to Haynes spec. Everything is purring along perfectly.

Post Tue Jun 12, 2018 9:11 pm

glad you got it sorted. did you take any pics ?

Post Wed Jun 13, 2018 8:33 pm

I always take picture as I go along.

Once Steve has the new forum up and running I will definitely post more often with pictures included.

It is too complicated and too much is involved with 3rd parties at the moment for my liking.

Post Wed Jun 13, 2018 9:16 pm

ok great, be good to see them. sure others would appreciate too. a quick guide with pics on the basic of a cam belt change. I believe your talking silly money in a bmw garage. 400 +

Post Thu Jun 14, 2018 8:50 am

I agree.

Even better would be if good forum posts could be elected to make it into the wiki, once the new forum is up and running.

A slightly more up to date wiki would be good. Not to detract from the fact is it an excellent piece of work already and is much appreciated, however as with anything it could be refined and improved further.

I'm sure all of this is probably on Steve's long to do list.