98 S70 T5: Peculiar vacuum leak after engine swap

[WhatAmIDoing]

I've phoned 2 friends, had another friend look at it, and paid a mechanic to find the leak. Nothing a foul has turned up. I've taken the snorkel out and replumbed it several times now. Smoked the car dozens of times, even isolating individual hoses. I've tried running with the MAF and/or O2 sensors unplugged, made no difference. It either runs lean or rich or normal and you never know what you'll get or for how long.

Could running too big of a hose from the PCV breather box to the snorkel cause issues? That's all I can think of for right now that is nonstandard.

Waiting on a big box of parts. I'm going to take the intake back off and replace every gasket, o-ring, and hose. Hoping for a win.

[abscate]

Is the PTC orfice original or drilled out? I was never a fan of drilling it out, it is an engineered vacuum leak on these cars

[WhatAmIDoing]

Is the PTC orfice original or drilled out? I was never a fan of drilling it out, it is an engineered vacuum leak on these cars

It seems to be original. This is the second one that came with the new-used snorkel when I swapped them out thinking that would fix the issue. Old snorkel was leaking at the rubber grommet around the PTC. Of course it couldn't be that easy.

[scot850]

Can you use a piece of hose to your ear and use it as a stethoscope to try to help isolate the area of the leaking sound? Obviously be careful near anything that rotates and could catch the hose!!

Not everyone had a mechanics stethoscope to hand so this is a cheap version.

Neil.

[WhatAmIDoing]

Can you use a piece of hose to your ear and use it as a stethoscope to try to help isolate the area of the leaking sound? Obviously be careful near anything that rotates and could catch the hose!!

Not everyone had a mechanics stethoscope to hand so this is a cheap version.

Neil.

A couple people and myself have tried isolating with a hose and stethoscope. Just can't pinpoint it anywhere. Have tried ether and propane as well. The idle is so inconsistent, it's hard to tell wether it makes a difference anywhere. Unfortunately my parcel looks to be delayed until next week. Was hopping to tear back into this this weekend.

[scot850]

Another question, sorry! Is the replacement engine the same type and year? Just wondering as there were differences in 1999 from 1998 that may leave a hole on the LHS of the engine block/head is a 99 engine was fitted to a 98.

Neil.

[WhatAmIDoing]

Another question, sorry! Is the replacement engine the same type and year? Just wondering as there were differences in 1999 from 1998 that may leave a hole on the LHS of the engine block/head is a 99 engine was fitted to a 98.

Neil.

The donor engine is from a 1994 850 T5. Coded B5234T.

[scot850]

I'm trying to remember on the 98 (I'm assuming you just used the block and head from the 94 and the intake/exhaust manifolds from the 98),
there is a pipe that runs under the intake manifold. At the distributor end it folds around the block going to the PTC.

I and others have made an error fitting the intake manifold by trapping a mounting bracket to hold the bracket between the intake manifold and the head giving a intake leak and hiss.

Neil.

[WhatAmIDoing]

I thoroughly investigated around the intake. I confirmed the bracket for the pipe work is on top of the manifold and not trapped between the gasket. There does appear to be more gasket sticking out on the right side of the intake than the left. But I'm not sure how the gasket could have got misaligned during install when it's trapped by the bottom bolts.

I pulled the fuel rail to redneck test the injectors. They seem to be fine, very even. This is when I discovered I had rolled and pinched 2 of the injector o-rings (smoking gun perhaps). I replaced all 5 with the IPD Viton o-rings and lubed them for the reinstall.

I also discovered the top of my dipstick had cracked. Stuck it back together with JB Weld and replaced that petrified o-ring as well.

Took it for another test drive this morning to get a full tank of fresh 93. Still has an occasional hiccup, and I think it is still idling too rich. But it drove much better and the LTFT stayed within +/- 2.5% of 0. Drove around for about 20 miles. Also, the weird hissing is still present, but it quieted down quite a bit. It's definitely isolated to near the PTC orifice.

Don't want to call it fixed yet, but I think catching and replacing those O-rings definitely helped quite a bit.