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1 month ago, replaced valve cover gasket as oil was leaking onto exhaust manifold (See pics). Still on the OE covers. I'm an idiot and I broke one of the valve cover bolts. Doesn't leak oil, when I pulled the covers the gasket was totally intact and not pushed out. Will be extracting the bolt and replacing all 12 bolts, as I clearly over-torqued them (stupid harbor freight wrench).
1 week ago, get a random engine icon and bing on the rev counter digital display while driving. No OBD codes are stored (I do not have a mini scanner), no CEL on the speedometer instrument. After this, the car won't make boost. I hear a loud whistle whoever the turbo spools in any gear, every time. Clearly sounds like any boost which is built is escaping somewhere. Car drives totally normally, engine feels smooth and makes power as you would expect without the turbo, the only symptom is lack of boost and the missing 100 horsepower. No codes, the icon has not happened again.
I checked the diverter valve, no rips no tears, looks fine. I checked the PCV diaphragm, mild rips and tears, but nothing serious. I'm going to replace both since I've got it all apart.
I noticed the PCV cover was slightly ajar before I removed it, some of the clips weren't fully inserted. And there is a crack in the cover. It also appears oil was leaking from the PCV as that whole area is wet (I cleaned the valve cover before reinstalling it), in addition to the oil cap (I've ordered a new one).
Any ideas what is causing the boost leak? Can the diverter valve fail internally without tearing\ripping the external seals? Can that damaged PCV valve cover cause the boost leak? Maybe the check valve built into the covers? I came across this thread:
If you have a “half engine” indicator on the tach display, the DME is artificially limiting boost due to some other issue. Need a BMW / Mini code reader to determine the issue and get it resolved.
When I replaced my valve cover I accidentally unplugged the vacuume line that controls the turbo boost. It is real easy to go unnoticed as the vacuume line is small and unplugs easily. The line is located near the turbo / Fuel pump area. Make sure to check if this hose is still connected.
I would just start with the diverter valve and the PCV valve as you planned: my guess is it's one of those. If your diverter is original those are known to be problematic; the latest rev is supposed to fix the reliability issues so if yours is original I'd just replace it regardless.
Some of the valve covers are crappy. The first replacement one I got did what yours did and was leaky around the PCV valve area. I don't remember what brand that was but I got another one (Uro brand from Pelican Parts) and it seems to be better.
Will be extracting the bolt and replacing all 12 bolts, as I clearly over-torqued them (stupid harbor freight wrench).
Honestly I never had much trouble with the (used to be, lol) $9.99 HF Pittsburgh torque wrenches. I had one stop clicking on me at one point, but otherwise they were always in cal when I checked them over the years. With all my clickers I got in the habit of putting the drive in a vise at the start of the job just to make sure they still clicked at what felt like a reasonable point.
Torque on those bolts looks like it's 10 Nm (7.3 ft-lb or 88 in-lb). When you're going that low you need to use a dedicated in-lb torque wrench, the only HF model I'd trust for that is the 1/4" one. You also really need to get a feel for it and stop just as it clicks: if you're going to fast it's easy to hit the other side of the click and overtorque the bolt.
If you want to try another wrench I found it surprisingly hard to find a decent-quality 1/4" model that wasn't Snap-On pricing. I ended up with the GearWrench 120XP and it's quite good, but a lot more spendy than the HF one. So if you're only going to do this now and again (and you have the 1/4" wrench...don't try this job with a 3/8") then check your wrench for accuracy, if it's not working right it should have a lifetime warranty and HF will replace it for free if you bring it in.
When I replaced my valve cover I accidentally unplugged the vacuume line that controls the turbo boost. It is real easy to go unnoticed as the vacuume line is small and unplugs easily. The line is located near the turbo / Fuel pump area. Make sure to check if this hose is still connected.
I'll take a look at it, but I'm pretty sure I didn't disturb anything unintentionally. And certainly not enough to pull any lines, the lines I've had to pull so far are pretty solidly attached and didn't accidentally come off. They all needed two hands and I only barely got them off.
The history of the car is unknown, but the covers say Polytec Group right on the front. I believe those are OE? They seem to be in pretty reasonable shape, I just hope I didn't crack or damage them from over-torquing them. Could cracked covers from over-torqued bolts cause a boost leak?
As for how I cracked the valves, I dunno. This is the first time I've ever pulled covers, and re-torquing the bolts I had 9Nm torque spec. Not sure why it was different than your figure, but it's basically the same. I just stupidly kept cranking because the wrench didn't click. Then it REALLY clicked lol.
I'll be picking up these parts and moving forward for now. Thanks guys!
Installed the parts. Hissing sound is still there and it's not making full boost still. It feels like more power than before, but it's hard to judge. There's a bost leak somewhere else, looks like I gotta go hunting.
PCV membrane had several small tears in it and was filthy. Good to have it replaced.
Original valve (it came apart on its own like this when I removed it). This looks like the original revision that fails a lot, the one I installed looks quite different.
Last edited by minifanboy; Mar 5, 2025 at 11:50 AM.
Oh, well that was silly. Forgot to clear codes. Had a 2774 "air mass too high", cleared it, we're back. Full power!
I wonder if this car has a tune on it, because that's one of the ways you trick it into making more boost right? Is there any way to determine that on my own? I know nothing about the previous ownership history.
