F40 Wastegate Hat Removal (long)

I was happily driving my F40 the other day when suddenly the boost was nowhere to be found. It would boost to about 6-8 pounds and that was it. Double bummer. The engine would rev freely, just with no/little boost. I parked the car and waited for it to cool down. I took it out again and, no boost. Ahem, it didn’t magically fix itself… ;-)

Given I had a car event in a couple of days, I didn’t have time to take it into Brian so I decided to research the turbo system and start tinkering. What fun! I put many hours into asking dumb questions, reading every scrap of info online, piecing together F40 manual info, and asking more dumb questions. I collected and measured a lot of data regarding the wastegate, its solenoid control value (and usage), and the BOVs (charge recirculation valves).

My F40 BOV Replacement thread also came from this experience:

http://www.ferrarichat.com/forum/showthread.php?t=246112

The thread below deals with the wastegate hat removal and cleaning. Although the BOVs were my boost issue, the working/clean wastegate unexpectedly solved yet another problem! I’m on a roll!

A number of fellow F40 owners have asked from time to time what’s involved with taking off the wastegate hat as that seems to be a good place to start looking for boost related problems. I took lots of pictures and the story follows.

Net/net: Although I pulled the wastegate hat and cleaned everything, I find it hard to believe that the wastegate would stick “open”. It’s very possible, but probable? That big spring is strong enough to overcome any slight wrinkling or twisting of the diaphragm. More likely that something would wedge at the wastegate valve seal – propping open the slide. However, if the engine didn’t crater, there shouldn’t be anything floating around in there.

My bet was on one of the recirculation valves (BOV) sticking open which would nullify the turbo in question. So, I decided to check those as well. (This turned out to be right on)

Note: The way I did it is not billed as “correct”; it's simply the way I did it. I’m sure you experts will set me straight where I screwed up.

Read on!

Tim

 

Since I was only removing the wastegate hat, I only needed access to the 6 hat bolts. To access the lower 3 bolts, you need to remove the heat shield and wastegate cooling “air conveyor”.

The air conveyor is held on by 3 bolts while the shield uses 4.
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When removing the 2 rear shield bolts, be careful not to lose the spacers that are in-between the shield plates. Turns out one of mine was missing from the last time the shop did some cat work. Those spacers are $35 – each!!!! Why am I not surprised…
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With the shields now out of the way, you can see the 6 hat bolts. The lower bolt head is on the outside because a mounting plate on the wastegate only has a 3/8” gap so the bolt can’t be mounted from the backside. Since the lower bolt also had a loose nut, I decided to take that bolt all the way off before starting to remove the rest in a star pattern.

Yes, the paper towels in the second picture were in case my fumbly fingers dropped a bolt or nut.
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Because the hat is under spring pressure, you need to loosen the remaining 5 bolts in a cross pattern a bit at a time so as not to crossthread/strip the bolts. It helps to have a second person to do this. I held on the hat against the considerable spring pressure while having my wife help remove the bolts.

Notice the gap in the picture below as I gradually remove the hat.
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With the hat bolts removed, I lifted the hat slowly off to expose the spring and diaphragm assembly.

I noticed that the wastegate valve was all the way “in” (shut) when I first removed the hat. This reinforced my thought that it probably was not the boost problem.

The second picture shows the flexible diaphragm pulled out a little so you can see its motion.
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The following shows the hat and spring. Note the wastegate adjustment screw. It puts pressure on the spring retainer and thus the spring.
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I removed the center nut on the valve shaft which freed up the diaphragm. I slid everything off and began the inspection and cleaning. The inside of the hat was fairly clean. The diaphragm was fairly dirty so I washed it with mild soap and water. However, it was in good shape and not in need of replacement. Ferrari sells the diaphragm by itself if needed: P/N 120750 Wastegate membrane.

Note how the diaphragm lip fits into its seat on the wastegate base.
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You can see how the collar fits onto the spring, and the (dirty) diaphragm fits into the collar. The diaphragm folds down around the collar and provides the up/down motion as the wastegate is activated.
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Closeup of the wastegate base. Note the air hole by the stem. This leads to the metal tube (seen on the right hand side of the bolt at 2 o’clock) coming from the wastegate actuator.

The center valve shaft was very sticky as I moved it up and down through its travel. The shaft appeared to have some copper based anti-seize lube on it (probably original). I also rotated it a few turns to try to get any foreign matter out from the seal (where the exhaust enters the wastegate in the other end that I didn’t have access to because I didn’t remove the whole wastegate).

I thoroughly cleaned everything and used some high temp (1600 degrees) lithium-based anti seize lube in place of the old copper stuff. What a difference! The shaft now freely moved up and down. This, as it turns out, had a profound effect on the car’s operation.

The diaphragm bottom fits into a groove on the base. Make sure to clean the groove well! I used a qtip which fit perfectly. When installed, the hat lip presses down on the diaphragm in the groove thus sealing it into place.
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It was cool how all the “hat” parts fit together so I made a few pictures of everything. The diaphragm has a large hole at the top, but doesn’t leak because it’s sandwiched together between the two collars of sorts.

I cleaned the diaphragm with soap and water to get it ready for reassembly.
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I folded up the diaphragm and placed it on its sleeve, then put everything back on the stem, replaced the nut, and finally placed the spring assembly and hat back on.
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When reassembling the hat, the lower bolt was a pain to get back on. I reversed the removal procedure by first putting on the other 5 nuts a little bit at a time in a star pattern.

Note: Make sure to orient the hat correctly so that the pin holes in the outer edge match up with the pin holes in the base!

Because the lower bolt and nut also had a washer and lock washer which had to go in the small blind gap, I had to hot glue the nut, lock washer, and washer, to the small open ended wrench.

That was the only way I could figure out how to get all the hardware aligned together in the small gap without dropping everything into the engine bay. Once I got it tight, I simply pulled the wrench off breaking the hot glue bond. Worked well. If someone has a better idea on how to do that, I’m all ears!
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With the wastegate reassembled, I decided to test it. I removed its manifold pressure hose (which inflates the diaphragm which pushes against the spring which opens the bypass slide which routes the exhaust to the center exhaust pipe.

I hooked up a bicycle pump (!) to the hose and cycled the wastegate a few times. You can easily hear the wastegate valve sleeve thunk up and down as the pressure it built and release. Cool. Although I couldn’t see when it first opened, it would fully open around 15-18 pounds someplace. Given I wasn’t going to mess with the preload screw, I only made sure the opening was in the ballpark of normal.

Time for a test drive.

 

The first test drive was after I cleaned the wastegate hat and replaced both of the “charge air recirculation valves” (BOVs).

The BOVs gave me back my full boost as described in the other (BOV) thread of mine:

http://www.ferrarichat.com/forum/showthread.php?t=246112

The clean wastegate unexpectedly cured another of my car’s problems!

My car (test pipes and Tubi) had the dreaded acceleration/fuel interruption when it apparently built boost too fast given a certain temperature and other factors. The change from “black” to “green” ECUs had some effect, but did not cure the problem. There are a number of threads on this subject.

I think “rexrcr” hit the nail on the head in post #11 in the thread:

http://www.ferrarichat.com/forum/showthread.php?p=264235#post264235

By me cleaning the wastegate stem and using new anti-seize lube, I effectively reduced the overall spring tension (I did not touch the adjustment screw). This did as Rob said and allowed the wastegate to open sooner than before.

This had two effects:
1) the boost came on slower and smoother (rather then the big bang boost effect).
2) no more engine cutout upon full throttle!!!!!!

Combined with the new BOVs which allowed the turbos to continue spinning during shifts allowing for faster re-spool up, the car became a dream to drive. Much more controllable!

The fans of the rapid boost might consider increasing the spring tension to offset the lower friction, but not me.
That’s it for now.

Time for a beer.

Tim

 

The GTO wastegate spring is non-adjustable? It has a solid diaphragm and hat from the pictures? – thx!- Tim