Horrible screech when accelerating.

[cookie79]

Hi was hoping that somebody on here might be able to shed light on this issue.

The problem is that under acceleration between 3000-4000 rpm the car makes a horrible screech sound, like a belt slipping on a pulley, if you ease off the pedal & accelerate very steadily the noise stops, seems to happen in 3rd & 4th gears but also occurs whilst in neutral & revving engine. The car has only done 150 miles since I rebuilt engine which was the 1st time I've rebuilt a engine so I'm worried my inexperience could be to blame, although apart from the above it runs lovely. The charger was rebuilt over 2 years ago & was kept in the house until it was fitted so again has only done 150miles, I'm keeping it under 4000rpm until I've done the recommended 500 miles.
I've checked the cambelt, thought the cover might be rubbing but took it off & no difference, also have single belt conversion & that doesn't seem too tight or signs of damage.

Not sure if this is related but also my boost gauge reads -0.5 at idle, I even bought a new gauge thinking that my original 1 had spent 9 years in a damp garage & was knackered, but the new gauge reads the same, although it was 9 years since I last had it road worthy I'm sure I remember the gauge reading 0 at idle & boosting to about 1 bar. I've been round the car for potential boost leaks but haven't found anything obvious.

Any ideas please?

[GR40]

-05 at idle sounds right! Your engine is in vacuum at idle so that is what you should be seeing. Now as for the sound it could be a hundred things. Can you upload a video? It would be very helpful and the fastest way to trace your problem.

[cheys03]

The symptoms described sound exactly like alt/aux belt slipping as you have mentioned. Various things to try - more tension, quick spray of WD on the belt etc to rule it out. Have someone rev the car to make the noise and spray the belt with WD40 at the same time. If the noise stops for a few seconds until the WD40 is burnt off then that's the fault. Do not do this on the cambelt though (and make the the cover is on). If you need to, is there any reason not to remove the alt/aux belt entirely and test only in neutral without driving the car? I must admit to not knowing much about how this would affect the charger or if it is safe to do so on a G40...

[kwijibo_coupe]

If the battery is decent enough running the car without the charger belt on will be fine just to see if it is that making the sound.
Don't drive it like this though as the alternator won't be charging the battery.

Is it the 5pk micro V belt conversion you have on the car? I ran one on mine for a while and noticed the belt would slip under hard acceleration. I then switched to a set of toothies and the issue was sorted. Also found my alternator was loose which wouldn't have helped.

[cookie79]

Thanks for all your suggestions I'll try all you mentioned to see if I can narrow it down, the belt conversion is the 5pk kit from max rpm. I've just took it out to video it making the noise, it was making the noise whilst driving then I pulled over to do the vid & couldn't make it screech, however  when I popped the bonnet & revved it off the throttle it then made the noise, I think it's all down to how the revs are applied to make it occur. Tried to post the vid but it won't allow it on here.

Thanks again

[GR40]

Post it on youtube and then post the link here!

[SuperMario]

Check the camshaft caps are put on the right way also.
Less of a option but possible.

As mentioned, remove the belt to rule it out if your having trouble identifying the source.

[cookie79]

sorry for the delay with the video took me 2 days fighting with various computers tablets & phones to finally get this on youtube, please check out the link below. & if the video is of a kitten falling off a chair or someone doing a crochet "how to" or any other video other than my engine then please except my apology.
https://www.youtube.com/watch?v=A4Ononl9XPE

[SuperMario]

Ouch that sounds knarly!!
I'd go against your belt slipping.
I refer to my previous comment still..
How much of a rebuild did it have?

[cookie79]

Yep sounds pretty awful eh! I'll try the belt scenario over the wk'nd when I get 5 mins, then if no joy give the cam journals a look.
The rebuild I did new pistons & all new bearings, oil pump, I had the head skimmed, & valves re seated with new guide valves, thought I was pretty meticulous when re assembling but you never know with me might have put a piston in upside down 

[GR40]

Well the good think is that this does sound like a belt slipping. I think one of you pulleys doesn't have enough contact surface with the belt and its causing it to slip I would try and tension it a bit more before removing it to see if that will fix it! If you don't know how much you should tension the belt here is a video that might help you! https://www.youtube.com/watch?v=FMiB3CnZpRc

[cookie79]

All fixed, no more awful screeching, thanks for the video it did help as my belt felt really loose according to the rule of thumb on the video.

Cheers