1982 Porsche 911 Blown Air Box?

[crodog1]

I have a 1982 911 that I have smoke tested. Lots of smoke on the drivers side, none on the right. Can't tell where smoke is coming from but it is there pretty quick. Maybe air box cracked? The box does have a pop off valve in it but the car is pretty new to me. I can't see any smoke coming from injectors or intake tubes but of coarse I can't see all the air box. Maybe a better way to check it? If it is the air box do I have to drop the motor?

[pmax]

Pics will help.

[crodog1]

There is a lot of smoke. Not so sure a pix would turn out.

[tirwin]

Any chance you can get a mirror in there to look on the bottom side of the airbox while you’re running the smoke?

Maybe a vacuum line is cracked or disconnected?

Outside of that you’ll probably have to pull the airbox.

[RedCoupe]

Wonder if the pop off valve itself is leaking. Maybe not seated properly?

[john walker's workshop]

Any screws inside the box that are sticking out a bit?

[pmax]

Originally Posted by crodog1

There is a lot of smoke. Not so sure a pix would turn out.

Post one without turning on the smoke to confirm you are connecting it correctly.

Given there's a smoke screen, check if your airbox is split. Pull up on the upper half and if you can move it or see a crack, there is your problem.

[groovydude]

The crack pmax is talking about can be very hard to see, it doesn’t take much. If your airbox is original that would be my guess. It’s a serious pain to pull but it might be worth it in the long run. You can check all your hoses, connections and components with the CIS removed.

[crodog1]

https://youtu.be/iunpco63ouc this is a link to the smoke test. Not looking too good.

[crodog1]

I do see 2 screws sticking up a little in the box. It does have a pop off valve in it.

[theiceman]

if screws are sticking up your box is likely blown. as a good explosion will force up screws.
I am in the minority but i dont believe a pop off valve does much at all, well except maybe stop it from starting when it does not seat properly.

[pmax]

Originally Posted by crodog1

https://youtu.be/iunpco63ouc this is a link to the smoke test. Not looking too good.

Neat smoke machine there.

Looks like it could be from the intake runner boot or the brake booster hose.
1982 911SC Vacuum

[gazzerr]

If it's the original airbox even without backfires it would leaking along the seams.

I pulled the airbox on my '82 and it had failed along the seam that runs above the 4, 5 & 6 runners. There was a big hole in the big rubber CIS "hat" that bridges the air plate and throttle body. The phenolic block that the cold start injector is mounted in just fell apart in my hands when I unscrewed it from the rear of the airbox. The smoke is coming from where that mount is. The rubber connectors that mount the airbox to the runners where cracked. You just have to disassemble it all and pressure test everything to see what's good and what's just worn out from 30+ years of heat cycles. It was amazing that it ran at all really. Another common problem is that the air box mounts in the rear sag and the metal lines in the rear rub through on the engine shroud.

It is doable to R&R it in the car but it's tedious and back breaking. I've done it but I wouldn't recommend it unless you just can't at least do a partial drop on the engine.

[crodog1]

I have tested it again and looked at the brake boosted hose real well and I can't see smoke coming from there. I am like the rest of you. Esp. since I had 2 screws lifted somewhat in the box itself. Guess I have a project coming up. Drop the motor or just lower it to get some clearance? Oh, thx for all your feedback.

[john walker's workshop]

80-82 with the frequency valve, i'd pull it. Way less pain.

[gazzerr]

At least drop it partially if you can. For a start you can't get to the clips that hold the rubber sleeves to the runners on the passenger side. The fasteners face to the rear of the engine compartment. The breather hose on the top of the engine under the air box needs to come out before you can remove the air box. It's tough to remove it with the airbox insitu. There is barely enough room to get the air box out over the fan shroud. The nuts that hold down the runner to the number 6 intake are difficult too. It's just a real pain. Dropping the engine will also give you the ability to properly test it for air leaks when you reassemble. You have to be super careful you don't drop anything into the intakes (e.g. washers). With the engine out it's much easier to capture these parts as you remove them. When you reassemble you have to assemble everything loosely so it all comes together properly and then tighten everything down. It's really difficult to do in the engine compartment.

[crodog1]

Looks like you are telling me pulling it would be best.

[gazzerr]

Originally I was chasing a broken oil pressure switch so I pulled mine and went through all of the CIS and replaced the injectors and injector seats, all the gaskets, O2 sensor, o-rings and rubber parts. It's a lot of work and it probably took me a good 2 months of weekends (I am slow) but it's worth it. The car runs really sweet now.

Do a fuel pressure test before you pull it apart so you can check the condition of the WUR and the fuel distributor.

Search and you'll find a lot of really good threads. Tirwin's "CIS for Dummies" thread is the go to reference here.

[crodog1]

Thx for the great info and threads. After reading the threads I think I am going to try and remove the air box without dropping the engine. Thx again Gary

[gazzerr]

No worries good luck. Try the partial drop it's not bad at all.