See63Run

I replaced my intake manifold gaskets, IM bolts, and PCV valve today using genuine MB parts. The IM bolts were torqued according to the proper sequence and specifications (10nm, 90deg, 10deg).

after the car warmed up, I went for a spirited drive and when I got close to home, I noticed a high pitched whining noise that I originally thought was an idler pulley. However, the noise persisted for a few seconds after the car was shut off and the pulleys had already stopped moving.

after doing some reading on here, I started the car again and pulled the engine dipstick while the whining noise was happening. It immediately stopped and I could hear air being sucking into the dipstick opening.

I checked all the IM connections and everything seems fine. The car was not making this noise before I took of the intake and PCV. Do you think it’s more likely that I have a leak somewhere or that I got a faulty PCV valve and that’s what’s causing the leak?

some people say it’s possible to swap the PCV without removing the intake manifold, but I’m really hoping I don’t need to pull the IM again. Not difficult, just a bit of a PITA.

Any ideas?

one other question, are the IM bolts stretch bolts / single use or can they be re-used?

chrisridebike8

Spray brake clean around the IM gasket while the car is running when it’s making the whine. If the idle changes, you have an IM gasket leak. Bolts are torque to yield (they stretch). You saved a few bucks by not changing the PCV valve. Bold move…

See63Run

thanks for the advice, but I stated a few times that I did change the PCV

chrisridebike8

my mistake. It’s one of those two leaking. My guess is the IM gasket.

BLKROKT

I know it’s not SOP, but I also put a pretty good bead of high temp RTV on my intake manifold gaskets (both sides) just in case to ensure a good seal. Has never leaked.

See63Run

the MB gaskets are pretty thin metal and I was thinking about adding some RTV but that stuff is such a mess to clean off of sealing surfaces in the future if I ever need to remove the IM again.

I'm going to see if I can get the new PCV off without removing the IM and swap it with the old one and see if the noise goes away. If it does, I may have received a faulty PCV from MB.

WidowrRacing

Curious to see what this issue is.

TPete19

Are you getting a CEL? If one of the IM gaskets were still leaking, you'd likely get a lean code for that bank (p0171/p0174).

When I did mine a few years back, the new ones still leaked. Mine didn't make the noise that you're describing but my CEL came back on. I ended up RTV'ing them just like BLKROKT did. No codes ever since.

I don't that you got a faulty PCV, but it's possible. Double check your vacuum lines' routing.

See63Run

No CEL. No strange idling issues. No power loss. Just the high pitched whine when the car is warmed up and at low RPMs. I did not open the intake so I don't think it would be an internal leak within the IM.

The parts are genuine MB but came from FCP Euro so I am not at all hesitant to take advantage of their lifetime guarantee on the gaskets, bolts, and PCV.

Here's my likely course of action:
-Recheck all connections to the intake
-Since I still have the original PCV and did not cut the clips to remove it, I'm going to try to replace it without removing the intake by reaching behind the intake. Some posts seem to indicate this is possible, others say its not. From my recent experience, I had to loosen the bolts on the crossover pipe in order to remove the PCV, which is impossible with the IM still in place so I'm really not sure how anyone would be able to do this without taking the IM out. Doing it for the second time, I really don't think it would take more than 30min to get it unbolted and out. If the old PCV doesn't solve the problem, I'll know I have a leak somewhere else (possibly the gaskets).
-If I can't get the PCV off or if the old PCV doesn't solve the issue, I'll reorder the gaskets, bolts, and PCV from FCP euro and replace everything again.

I don't think there's any other obvious 'while you're in there' type maintenance items to attend to, but if anyone is aware of any, please let me know. My injectors have already been replaced, as have the coil packs, spark plugs, and valve cover gaskets. The only other thing that comes to mind is the air temperature sensor plugged into the back of the intake manifold.

BLKROKT

Don’t forget to spray the carb cleaner around the IM. It may help you to narrow the search.

Did you have a good look at your throttle body mounting plate while you had the IM apart? They’re known to degrade over time and leak. If it’s looking corroded and nasty you might want to change that out too.

See63Run

thanks for that reminder - will try that first because it’s the simplest diagnosis.

i didn’t open the intake at all so don’t have any idea what the condition of the throttle plate might be. Seem quite a few examples of ones that have corroded on this forum as on Tasso’ channel.

now that I’ve had the intake out, I’m much more comfortable cracking it open if I have to and rebuilding/replacing as needed. Would be an easy time to swap in some larger TBs

eightysixtuned

any video you could share of the noise?

skullbox15

If you open your manifold, please share some pictures of the TB plate.

See63Run

good idea - I’ll take it for a drive tomorrow and take a video. I took a short drive yesterday and didnt hear it but it was only 1-2 miles in each direction

See63Run

will do but hoping it doesn’t come to that

See63Run

Update....I think I found the issue.

I sprayed some brake cleaner around the IM gasket and did not notice any chance in idle so I don't think the IM gaskets (or the torque applied to them) were the problem. I tried to remove the new PCV valve without removing the IM and found it to be impossible. Between the tight space, difficult angle, and coolant crossover pipe in the way, I'm not sure how anyone could remove the PCV while the IM was still mounted. I know people have claimed to do it, but I really don't see how it's possible. I then removed the 10 bolts holding the IM to the heads and lifted the IM up and out of the way. Because it's very difficult to remove the small hard line entering the rear of the IM (there have been some other posts on this challenge), I could not remove the IM entirely and instead rotated the entire IM towards the diver side such that the front of the IM was facing to the right (when looking at the engine from the front). While doing this, I noticed that there was a pinch in the hard plastic line approximately where the rearmost ignition coil is mounted to the valve cover. There is also a small T25 screw here that holds the plastic line in place near the valve cover. I think I had pinched this line when I removed the IM a few weeks ago and this pinched line was causing my intake issue. I'm not exactly sure if this would cause the issue, but other than a faulty PCV or IM gasket, nothing else on the car was changed.

I can't find this line on a parts diagram, but it goes into the rear driver side of the IM into a rubber bung that cannot be easily removed from the IM. From the IM, it runs along the valve cover (zip tied in with some of the ignition coil wiring) and to a small valve near the front of the engine that has an electrical connector attached to it. It is also clamped at the front end with a non-removable clamp.

Any ideas?

edit: adding some photos

See63Run

after watching one of Tasos' videos on the IM, the thin hard plastic line running from the rear of the IM to a solenoid/valve at the front of the engine appears to be for the charcoal canister. in his video, he removes the original metal clamp in order to remove this line from the rear of the manifold

edit: Mercedes calls it a 'purge line' and the part# is A1560100470. it does not appear to come with the necessary clamps on each end (at the IM and at the solenoid valve)

Cwagon

Did you replace the O ring where the brake booster line goes into the rear of the IM.
He stated in one of his videos that that particular O ring has a habit of splitting if you insert the tube dry or use and old O ring.

See63Run

no, I didn’t, but I didn’t see one on that line. In his video, that’s the line that you have to push in two clips on the side and the line pulls out. Are you sure there’s an o-ring there?

Cwagon

I found one of his videos where he mentions all the seals/ O rings required.
Not the video where he explained about what happens when it splits.
Look from around the 4.30min mark.

See63Run

you’re absolutely right - he mentions it twice - once when the parts are on the table and once when it’s assembled. Unfortunately he never shows insertion of that o-ring.

i can’t find that part listed on any diagrams for the intake. Anyone have any idea what the part number is??

See63Run

Thinking this through some more…

wouldn’t I notice a different pedal feel if the brake booster line wasn’t sealing properly?

See63Run

update - problem is resolved. took a nice drive last weekend with some spirited driving and didn't notice any noises and did not have any suction from the dipstick.

I replaced a number of things because I had the intake off (again), so i cant be 100% certain what the issue was, but my guess is that it was a pinched vacuum line (see post #16 above). thankfully, I was able to unpinch the line with a pliers without cracking the tubing.

for those that might find this in the future, you will get a lot more room to maneuver the intake without removing the small vacuum hose IF you unscrew the clamp holding it to the valvecover at the rear of the drive side bank of cylinders. this provided a lot more room to move the IM around without pinching the line.

-bolts
-PCV
-manifold gaskets
-brake booster o-ring
-brake booster locking clip
-brake booster insert

for the three brake booster items, see post #6 in the following thread where i listed the part numbers that i ordered.

thanks to cwagon above for providing info on the o-ring. i do not think this was ultimately my issue, but it gave me the opportunity to do a thorough check of something I wouldnt have otherwise checked.

https://mbworld.org/forums/c63-amg-w...cuum-line.html

Cwagon

Glad it's all good now, no matter what it was in the end.

See63Run

tasos just posted a new IM video and the parts for the brake booster clip are pretty clearly shown in this video, including the o-ring.