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N62 Z3 Part 24: Test Drives & CCV Saga

I took the car out today for a long drive, it's so much fun and boy is it fast. On the last stretch headed home I started to floor it for the first time. Was recording a run when - BOOM - something happened. Steering wheel vibrating horribly. Oh my god... I thought the steering linkage broke but I still had steering... then I remembered the front tire was rubbing and near the end of it's life. Pulled over and took a look - sure enough I blew the front tire. I put the wheels on just as rollers, wasn't expecting to be driving it on them. But then I started to think eh, the tires are shot anyways, nothing to lose really... (except maybe the pair of underwear I was wearing! haha)

Needless to say - I have never been so happy to see a flat tire in my life

Hitched a ride home hanging on the outside of a box truck that just happened to be driving down the street. Took my jack, impact and a spare tire from my other Z3 and drove down to replace it. Drove the Z3 home then biked back to the truck and got home. The whole thing probably took 10 minutes. But I'm sad the drive was cut short, I was having so much fun. Oh well - time to get wheels that fit! This was also a pretty good test of the steering linkage... I feel pretty confident in it now. I was also testing it on the drive, I took it to some curvy roads near me. The feedback is surprisingly precise. I would say 90-95% of what a stock Z3 feels like. So I'm completely happy with that!

I have a good set of wheels and tires in storage but this happened while my fiance was driving my X5 which has the storage unit key on the keychain. So I focussed on some cosmetic stuff in the meantime

The trunk panel here will need one more skim coat of filler before primer and paint but I love how it has come out so far

Later that day I pulled my Apex wheels out of storage, fresh rubber! Maybe the best set of tires I've owned in my life... haha

And even better news - I have clearance at the strut! I don't know why the last set of tires was rubbing here, but I am fairly confident that was a major contributor to it popping...

Next is a string alignment to try to take out any excess toe to prolong the life of these tires

I didn't photograph the string alignment process but I got the front wheels pointing the same way and took it on a longer test drive. At the end of the drive the brake fluid light was coming on... I noticed the clutch pedal was a little damp as well, I suspected the supply line nipple wasn't seated correctly in the master. Closer inspection revealed the supply line hose was popped off the supply nipple. Easy fix... I routed the supply line a little differently so I could get good leverage on it. Should work fine like this

And I was tired of getting comments on the steering wheel being upside down so I took the 5 minutes to fix that

The car is still smoking a little bit and I think it may be related to the CCV hoses. The intake manifold is oily inside, I looked at the CCV hoses on my N62 X5 that doesn't smoke and it has the external PCV bank 1 hose. There was also a service bulletin about it in 2009 - just at the end of the N62's lifespan - and they retrofitted the external PCV line hose to all variants of N62 at this time. BMW said it was due to cold weather conditions but if that was the case I imagine the insulated hoses would have been enough - but they also added the external PCV onto the bank 1 hose with this service bulletin. So I think I need to install the ugly PCV hose, at the bare minimum I'm going to start there and see if the smoking subsides

There was a small amount of oil pooled just behind the throttle body and the inside of the manifold was coated with a thin layer of oil

I let it idle for a few minutes then gave it gas and it did not smoke at that time, which it would do if it was valve stem seals. It seems to only smoke after the engine has been off for a little bit - indicating to me that there may be excessive oil vapor in the manifold which, when the engine is off, cools and condenses at the bottom of the intake manifold, where it is sucked up next start. It smokes a little bit at first startup then gradually smokes less and less as it is driven. If the external PCV line doesn't fix it, I may install a catch can to at least know where the issue is... CCV or elsewhere

With the ugly external PCV line installed

Also took a few minutes to add a turn-down exit

It's a temporary solution - eventually I will cut it off at the straight section before the turn down and add a flange and build out the rear section, but for now this will keep the exhaust from heating the differential

Speaking of differentials, I have a 3.15 Torsen to drop the ratio down from the 4.10 and it looks like it can't come soon enough

And the new to me differential

The bushing in the stock diff looked very odd and further inspection has revealed the subframe bushings are cracked, allowing the diff to sag at rest. Likely both the subframe bushings and the diff bushing were original to the car and with an engine producing double the torque of stock they accelerated the failure of bushings already at the end of their lives

The good news is the trunkfloor is mostly still intact at this point. It isn't perfect but I have had cars worse than this that, when monitored, didn't get worse for years. Admittedly those were S52 cars (making a fair bit less torque than the V8) but I am hoping with stiff subframe bushings installed I can prevent total failure

I also got one of my M diff covers out of storage. I had some choices but I chose to use the worst of the bunch... just because, otherwise I likely won't have any application for this cover in the future and it isn't worth much used. This came off an M roadster I parted out a few years go and it had some damage to the lower fin area

I simply decided to clean it up and clean the edges of the break. I may cut off the entire bottom section, to leave the fins "floating" but I am not sure at this point and it's not a priority given what I discovered with the subframe bushings

I do still need to clean it properly, but again not a major priority. I need to replace the subframe bushings first and foremost

I was also researching N62 CCV problems in the meantime, trying to learn if I need to do new valve covers, replace the orange diaphragms, or if its perhaps a different issue altogether

Boring CCV tangent below

I was also researching N62 CCV problems in the meantime as it is still smoking a little bit at idle and in fact it got worse with the external PCV line hose, which led me down a long rabbit hole of researching N62 CCV/idle smoke issues. I did get confirmation that the external PCV line is ONLY to be used with the updated valve cover which removes the internal CCV diaphragm on bank 1. Running the external PCV with the integrated CCV on bank 1 effectively blocked the vacuum off from bank 1, forcing all the vacuum to be pulled from bank 2, where the hose feeds to the bottom of the intake, right to the mouth of the intake ports. On this note, the more I think about it - the more it seems likely that the revised PCV hoses on the last years of the N62 were a bandaid more than a remedy - as it supplies both valve covers with vacuum from a single port on the intake manifold vs the previous styles, such as mine, where each valve cover feeds off it's own vacuum nipple to the intake. Supplying both valve covers from a single vacuum nipple seems to me it would halve the vacuum seen at each valve cover.

I am considering retrofitting this line, but before I do, I need to decide if I want to throw new valve covers on first as those will knock out two other possible culprits - the orange CCV diaphragms and the valve cover itself. The valve covers have an internal labyrinth of vacuum passages which can become clogged. The valve covers - I'd go with the Uro/APA valve covers, as so far their products have been great - are the updated style, requiring me to run the external PCV line, so before I order the revised line (it comes with the external PCV and without) I need to make a decision on if I want new valve covers or not

There was also a SIB in which BMW changed the minimum valve lift. The minimum valve lift can be set anywhere from .1-.8 - the SIB and most discussion around it seems to indicate this was done to fix idle issues, but as time has gone on (there are several long running threads in various forums about this topic), I have observed more people talking about this in reference to idle smoking. I have three N62's here currently so I am going to compare all of the values these have then look at mine. Mine idles smooth as silk, just smokes a little bit, so I am wondering if maybe my lift is actually possibly set too high - and that by reducing the minimum lift it would reduce the vacuum in the manifold at idle

End of boring CCV tangent

Another idea is to simply steer into the skid by renaming the car from "Dunklenator" to "Lil Smokey"

..."Lil MIGy" also crossed my mind but technically I run FCAW and right now I'm frankly FCAWing annoyed with it haha

On that note if I decide to do the trunkfloor myself I will hook up some gas and run it dual shield...

For the subframe stuff I ordered the Tuner solid subframe bushings. I've always wanted to try the solid subframe bushings and this seems like a great test bed for them. Maybe it would stop the trunkfloor issue from progressing altogether. Turner recommends using them with a solid diff bushing but I don't see any real reason for that. I'd rather let any deflection be absorbed the bushing and not the trunkfloor. Though of course ideally, the solid subframe bushings will not allow any deflection in the first place. I also have new trailing arm bushings ordered as well - for those I am using stock rubber to try to minimize NVH to whatever extent I can. Diff bushing I'm going to use whatever is in the cover I end up running, as both the 3.15 and the M diff cover have decent looking bushings. Those are super easy to replace later anyways. Rear sway bar bushings I'll do later as I will likely end up upgrading the sway bar so I don't want to order bushings until I'm set on what bar I'll run

More CCV talk!

The more I read forums and etc the more mixed answers I got. I decided to try to research how the CCV valve itself works to try to get an understanding of the system. As I understand it, what is supposed to happen is at high vacuum conditions, the vacuum pulls the valve closed

Here is the CCV valve/diaphragm in question

I used a flashlight shining into the CCV port to see where the vacuum comes from. It comes from the middle

At "rest"

But the diaphragm can be pushed in

This side, after fiddling with it and pushing it, left a clear mark where the center nipple contacted the valve cover. The shadow of the pick tool shows the mark left by the center nipple itself, the metal of the pick tool shows where this diaphragm leads under the valve cover (direct access to the oil vapor in the valve case)

The other unfiddled with side showed no signs whatsoever of this contact

I believe - and I am not entirely positive - that what is supposed to happen is the high vacuum pulls the center nipple against the valve cover, sealing the diaphragm thus preventing the engine vacuum from pulling in crankcase vapors at idle

I used aftermarket diaphragms (vaico) and there is a spring between the diaphragm and the diaphragm and it seems to me that what may be happening in my case is the spring pressure is too high for the diaphragm or the rubber is too stiff, preventing the proper sealing action from occurring

Oh and just some normal Arizona stuff...

Later that day I dug the original diaphragms out of storage and installed them. The rubber is noticeably softer - like, completely different feeling

The springs were also slightly different, but not by a lot. I installed the original diaphragms and the softer springs and started it up, pulled the oil cap, no vacuum! Throttle response improved too. The vacuum was so high previously that when I pulled the oil cap there was nothing coming out, I just heard and felt air going in. When I pulled the oil cap this time oil was spraying out. Which was a great sign! There was virtually no vacuum at all I haven't ran it too long as it is on jackstands and it is still smoking -burning residual stuff I imagine - but I hope after sorting out the rear subframe stuff I can go for a longer test drive and burn out whatever is left in there

It was still smoking, but the CCV's seemed to be working though. I started to worry it was a head gasket... pulled the plugs, compression tested... everything looked good there but plugs 7&8 were oily. Hmm. I was wondering if it was still residual crap burning out. Looking in from the throttle body I just couldn't imagine how much oil could be in there. I heard reports online that there is enough space for oil to pool but looking inside its impossible to tell

I didn't like the smoking and I wanted to get a better understanding of the intake manifold design. I had a spare intake manifold in my storage. Dug it out and tore it apart... the fancy schmancy variable intake mechanism is attached to the "lid" and the bottom section looks like this. A nice little tub for potential oil pooling

You may also notice the "lower" port supplies towards mostly bank 2. When I ran the external PCV on bank 1 previously this forced all the vacuum into this port which seems like it may have filled the intake with oil as some have described

Beyond this - I used my level to check the engine and the engine is leaning rearwards and to the driver's side with the way the car sits on the jack stands. So any oil pooling will pool right in front of cylinder 7 and 8. The ridges in the bottom would also keep some pooled in front of cylinder 7

The rotary intake runners also have a second "inlet" which is open to the bottom at idle (feeding directly from this lower area)

So on my engine in the car, I manually set the intake runner to the "high RPM" position where these lower inlets were not open to the lower pan. I started the engine and idled it a bit and there was no smoke. I revved it hard, then the intake manifold reset to it's normal operation position and at idle the runners were open to the lower pan and it once again smoked

For now I am still thinking it just needs to burn off residual stuff. But I have a better understanding of the system now at least. I think I am also going to go forward with my plan to cap the lower port and run the N62TU upper hose that splits the CCV to both banks

Enough about CCV's though! Next up I focus on refreshing the rear end!



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