Testing for boost leaks

ferocity02 · Post by **ferocity02** » 01 Oct 2018, 22:03

Anyone have a good write up for testing for boost leaks on a S70 GLT?

On my BMW 335 it's pretty easy. Just remove the air filter and replace it with a PCV cap that has a schrader valve for pumping in air. Then you just have to remember to block the PCV hose so you're not pressurizing the crankcase. The intake valves hold in the pressure at the engine side. On this car I would pump up the system to about 25psi since it's boost up to 20psi.

You don't need to use smoke or soapy water, it's usually easy enough to listen for the leaks.

I assume this can be done on the Volvo S70. I figure I should block the PCV line going from the PTC valve to the oil vapor trap, and leave the oil filler cap off just in case. Anything else to block? I would probably pressurize to 10-15psi.

Post by **hausmeister** » 02 Oct 2018, 01:30

There is nothing special to look out for imo. I guess you are talking about a turbo car? Buy a tester kit (2 hose plugs with valve and pressure gauge), block off the hose from the turbo outlet and block off the hose before the throttle body. Block off the Idle air hose with random object. Apply pressure. Profit.

The engine is not air tight so you can't use that. At least I don't see how short of plugging the exhaust.
Even if it was I wouldn't apply ~2 bar to the pcv system, it's likely to blow apart.

Post by **abscate** » 02 Oct 2018, 04:21

I don’t think I’ve seen this done here, but it is much easier just to remove the induction path and inspect components , with the exception of the intercooler.

There is a weep hole on the intercooler to remember , too.

Also remember the PTC is just an orfice, not a valve.

ferocity02 · Post by **ferocity02** » 02 Oct 2018, 21:57

hausmeister wrote: ↑02 Oct 2018, 01:30 There is nothing special to look out for imo. I guess you are talking about a turbo car? Buy a tester kit (2 hose plugs with valve and pressure gauge), block off the hose from the turbo outlet and block off the hose before the throttle body. Block off the Idle air hose with random object. Apply pressure. Profit.

The engine is not air tight so you can't use that. At least I don't see how short of plugging the exhaust.
Even if it was I wouldn't apply ~2 bar to the pcv system, it's likely to blow apart.

The intake valves will block any of the air from getting through the engine, assuming the valves are all closed (there may be some slight air hissing through the valves). But you need to be especially careful not to pressurize the crankcase, or else you can damage seals or pop them out entirely. Hence leaving off the oil filler cap as a safety precaution.

Ideally as much of the system is pressurized, including the turbo compressor side and the intake manifold, to test as much of the system as possible. There are many hoses and the vacuum tree entering the intake manifold, so its especially important that it's pressurized. Capping off the system just before the MAF sensor is an easy location to do it. The weep hole in the intercooler would need to be capped as well, maybe duct tape would suffice since it's a tiny hole

WhatAmIDoing · Post by **WhatAmIDoing** » 03 Oct 2018, 07:45

If you don't know the age of you hoses and vacuum lines and/or are pretty sure they are original, it's probably better to just replace them all and then search for boost/vacuum leaks. Old, rotten lines might not like being pressurized, and it's easier to replace lines when they aren't blown off and you know where they go.