Sprinter 311 "gasping for air?"

[Cnics]

My Sprinter has developed an odd noise recently (actually 6 months but its never got any worse) which can only be described as gasping for air.

It makes this noise without fail when you take your foot off the throttle at between 1500 and 2000 rpm. it is mainly in the higher gears if you are pulling at say 1800rpm you can hear something build up (possibly pressure or a vacuum) and letting your foot off the throttle only slightly causes this noise. is is not an "air" noise more a noise of something intaking air quickly.
its done it before and after a change of air filter. i can't check under the bonnet very easily as it only does it under load (when moving and in the higher gears at that).

it has been doing this since before the other problems i have mentioned in another section occurred.


Rob

 

[dava]

Prone for splitting intake pipes to manifold, gives a woosh noise though, more details would help.

 

[Cnics]

I wouldn't say it was a whoosh noise.
more a short sharp intake or something. it is literally a 1/4 of a second long.

Not really much more i can tell you i'm afraid. when you accelerate in say 4th from 1500rpm it sounds like something is building up, and then a slight release of the throttle (or fully, but doesn't have to be more than a bit) and you get this noise.

Doesn't do it above 2000rpm doesn't do it below 1500rpm. theres no loss of power or anything like that. Doesn't do it in 1st of 2nd, possibly under load on a hill in 3rd and 4th and 5th on any gradient. it seems like a load issue.


Rob

 

[dava]

Still think it could be the air intake hose, it's the big black one in front off you as you look under the bonnet. They split underneath and under load the expand as the boost goes on and the split opens to allow the pressure to release. Get some one to rev it and have a listen under the bonnet and carefully run your hands around it to feel for air escaping, it's a very common fault so start there. Another thing it might be is the exhaust manifold bolts loosen and allow exhaust to leak, but this gives a chuff and you dont normally loose power.

 

[Cnics]

Thanks, i'll check the pipes and the bolts.

Rob

 

[philsparky]

hi,just reading about your problem,it wont be a split pipe cos if it was or if you had got a fault on the cdi system the vehicle would go into "limp" mode i.e. it would not rev above 3000 rpm .as your fault does not have this problem i suggest that its probably the variable vein turbo sticking causing an overboost just for a split second and releasing the pressure down the exhauast giving a whistle when you release the throttle.my advice ,make sure the vaccuum controlled lever mech on the turbo is free ,if it is ,hobsons choice unfortunately,try a new turbo