Thread: NOT the inlet air leak - 300Tdi Discovery 1997

Have you checked the Boost Compensator Diagphram (BC) isn't split or punctured inside the body of the B/C, Regards Frank.

Leo,
That's a very nice, clean engine for a 1997 vehicle!
Impressed.

Originally Posted by Tank

Have you checked the Boost Compensator Diagphram (BC) isn't split or punctured inside the body of the B/C, Regards Frank.

No, I haven't Frank. As mentioned, the compensator seems to be working fine - no loss of power.

And the actual cause of the noises will be revealed in Part II shortly.

Originally Posted by AndrewMilne

Leo,
That's a very nice, clean engine for a 1997 vehicle!
Impressed.

Thanks Andrew. It looks nice because it had a very thorough wash-down before a new, very shinny, Turner Eng. UK 'performance' head was fitted about two years ago. And repeatedly washed-down while I was chasing and fixing the injector pump leaks a few months ago. And again washed-down after the No.3 injector pipe cracked at the injector union a few weeks after that...

So, dear readers, it was now time to check the main inlet system for leaks. First applied 20 psig to the inlet manifold via the intercooler outlet hose (photos below).

No sign or sound of leaks. Soapy water produced only the tiniest bubbles from the gasket near No.3 inlet port - not enough to be my problem.

So then repeated the process by applying air pressure to the turbo outlet elbow hose (the one that can famously de-laminate and choke the engine completely!). So now the system is pressurised from the turbo outlet elbow, through the intercooler and right up to the inlet valves - and again no sign or sound of leaks.

Put everything back together and went for another test drive - and, yes, the noise is still there! This is getting very strange.

The next step was to pull out the intercooler to see if it has a crack or similar that only made a noise under the pulsating inlet flow, rather than steady pressure. So, I put it 'spigots-up' on the floor and filled it with water (and a bit of washing powder, even though it was relatively clean). No water leaked out.

THEN I looked at the short hose between the turbo-to-intercooler pipe to the intercooler inlet spigot. See below what I saw. The hose had de-laminated in the small gap between the two metal pipes, less than 20 mm wide. But no sign externally and no actual split or leak from the hose. Could this be the source of the noise?

Finished cleaning up the intercooler and connecting pipe, fitted a new hose and went for another test drive. And Hey Presto - the noise is gone!

Has anyone else encountered this?

Forgot to attach a couple of pics of the rig used to pressurise the inlet manifold while testing for leaks:

Ian,I'd go through all the hoses and pipes and change them all,turbo,intercooler,charcoal canister and it's hoses and the injector spill lines,all of them are cheap from the UK except the spill lines and boost compensator line,buy a meter of both from your local diesel shop and cut to length,they rub through against the head and worse the acoustic cover and the compensator rubs through everywhere.The key to reliability is to look for rub points,you'll see polished area's especially were hoses etc pass over/under/around other parts,while your doing the charcoal canister I'd do a valve set and check the lash caps,your got to take the cover off anyway so I'd do it while your there,this sounds like lots of work and expense but it's simple stuff and Tdi parts from the UK are as cheap as car parts can be. Pat

ive seen that before.

its caused by the weight of the pipe and vibration.

if when you pull the hoses off take it off of the intercooler side not the pipe side and check to see if its stepped, if its stepped replace it.