1995 S4s Won't Build Boost, Loud Whooshing Under Load- Blow off valve or wastegate?

[drdoom]

An audible "whoosh" is just so typical of a BOV. I'd double back onto that trail, can't think of anything which could generate a comparable sound. 

[ramjet]

Easy way to check your plenum gaskets. Start the car. With a small diameter piece of plastic tube, one end in your ear and run the other around the gasket position. If it is sucking or blowing, you’ll hear it as clear as a bell. 

[Bomb Factory]

Makes sense.

It looks like only modifications to the stock vacuum lines to accommodate the BOV is a T that goes into one of the lines running on the back side of the engine. It seems pretty simple to just pull it and place a cap on the T or even just use a barb splice to reconnect the stock hoses.  The vent tube is external and just hangs down so that is pretty easy.

Suggestions on where to get a good replacement hose to span the intake to the charger cooler?

I will definitely test the plenum too.  @ramjet thanks for the tip there.

[Bomb Factory]

@jonwat so its just the one part number that gets me both parts of the gasket or do I need to order two?

 

[Erikl]

SJ will sell the stock piece of silicone tubing to replace the Tee where the BOV is.  Or you can buy the correct diameter from hundreds of vendors on E-bay etc.  I forget what the diamter is 2.5" or 2.25" I believe.   You get what you pay for their, quality all over the map.

In 5 minutes you can pop the BOV out and manually push the plunger in and out and see if that is likely the problem.  My last one could be disassembled and I could see where the plunger had deteriorated and was sticking.  

[jonwat]

11 hours ago, Bomb Factory said:

so its just the one part number that gets me both parts of the gasket or do I need to order two?

Give them a call & ask, they were always helpful to me whenever I had a query 

[Bomb Factory]

Finally got time to remove the BOV and replace with a new silicone tube/hose.

That seemed to do the trick.  I can now peg the boost gauge at its 1 bar limiter.

PO on mine had the gauge recalibrated since he has a red race chip that ups the max boost under the right conditions.

I want to get the car on my dyno and I am thinking that Id like to have a more precise boost gauge before I do.

Any advice on replacement/upgrade boost gauge that others have found to be of good quality and functionality?

Also- I noticed that one of the little rubber mounts that holds the charge cooler to the head is severed. This would be the one towards the back of the car and is hard to see since it is obscured by the charge cooler.  Id like to replace it but dont know what to call the part to search for it.  Any info on what the part is called or a PN is also appreciated.

Happy to have all my boost back.  Now I need to learn how to use the boost properly- I find this car requires you to wring the power out of it- vs the large V8s in the rest of my cars. Im getting to know it slowly so I can feel the limits and keep better control.

 

 

 

 

 

 

 

 

 

[Erikl]

The vendors know what its called (JAE, SJ) its super common...I replaced mine and imediately broke the new one moving the Charge cooler around re-installing ...grrr.  

If you have the manuals you can see the Part number in the Parts manual.

[jonwat]

5 hours ago, Bomb Factory said:

Also- I noticed that one of the little rubber mounts that holds the charge cooler to the head is severed. This would be the one towards the back of the car and is hard to see since it is obscured by the charge cooler.  Id like to replace it but dont know what to call the part to search for it.  Any info on what the part is called or a PN is also appreciated.

Rubber Mounting, chargecooler rear 

[Erikl]

Buy a spare so if you break the first one....🤪

[Bomb Factory]

Link provided says part no longer available.  But since I have the PN I am sure i can find one.

 

thx!

[jonwat]

57 minutes ago, Bomb Factory said:

Link provided says part no longer available.  But since I have the PN I am sure i can find one.

 

thx!

SJSportscars 

[Bomb Factory]

Found it ordered it.

Looks like the rear one is a real pain in the ass to change out!

[Escape]

Nah, they're easy enough. The ones Lotus uses have a hex so you can use a spanner or long socket. On Monday I was working on an old Peugeot, same mounts but without the hex and if you grip them with pliers they tear off...