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Tuesday, April 23, 2024

Doug's Domain

Doug Vetter, ATP/CFI

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Saturday, November 5, 2016

CEL Followup

Not long after I posted my last entry a long time reader of the blog emailed me to let me know that the problem I'm having with the evap system was most likely related to the expansion tank (Item 1). He said that it's a fairly common problem with these cars and if I hadn't experienced the failure yet I was overdue. Frankly, given the location of this part it's no surprise that I had not heard of it before or understood its potential failure modes.

(Image: Closeup of new fuel supply expansion tank)

Research on the topic revealed that the problem is caused by poor design of the nipples on the tank -- first, because they're made of plastic, and second, because the small brass tube they use to reinforce the crappy plastic nipple does not extend much beyond where the hose attaches, making it pretty much pointless. So naturally vibration and heat eventually cause the plastic to become brittle and crack, thus producing what is categorized as a "minor" leak similar to what one might experience with the gas cap secured improperly. Left alone, the nipple can break off entirely, leading to a "major" leak.

While waiting for the parts to come in I read about the evap self tests the car goes through on every drive cycle to verify that the fuel system is sealed and discovered that after 150 miles a persistent minor leak will be reclassified as a major leak, because the system looks at total emissions, not just the current rate of those emissions. I also learned that the system *should* extinguish the CEL by itself if the leak no longer meets the criteria that triggered the warning in the first place. I found that revelation particularly annoying, since I've always run over to my technician to clear warnings created by a loose gas cap and now I'm not so sure this was necessary, particularly given what happened next.

While doing errands the other day I looked down after a few stops and suddenly realized that the CEL was no longer illuminated. Coincidence or not, the fuel level was down to about 1/3 at this point, while the CEL was originally triggered when closer to 3/4 full. Since I did nothing to fix this problem my guess is the thresholds are related to the fuel level (and hence air space and rate of change in pressure in the tank) and I seem to recall reading something about that as well, so I still plan to go through with the work.

Unfortunately, an incident last week involving my right index finger and a deathly sharp serrated knife (made in Germany, of course) will delay any work with my hands for a couple weeks but I'll get to it eventually.

More Engine Overhaul Research

After recently learning that M52 long blocks are no longer available from BMW I decided to call a couple of well known performance shops in the area to see if they wanted to rebuild the engine for me. Unfortunately they both declined.

The shop with obvious BMW experience said they didn't want to get involved in the project because they didn't want to "support a stock engine". I wasn't sure what they meant by that. They did begrudgingly put me in touch with the machinist that does all their work. I spoke to him and his only warning was that BMW engines cost big money to rebuild, at least as compared to the garden-variety LS motors. I didn't exactly consider this a news flash. His rough quote for parts and rework? $8K. That is about what I expected, and it's not far off Metric Mechanic's engines which are in the 10-12K range to start.

I do have other machinists local to me but they don't seem to advertise BMW-specific knowledge. Why is this critical? Besides the obvious benefit of knowing exactly what to expect and what works best on these engines, I would expect such a shop to have a torque plate and use it when boring/honing the block. I also don't want to pay a machinist to build or buy a torque plate for what I consider a ubiquitous engine.

Incidentally, I learned recently that BMW does not use a torque plate on these engines in manufacturing and that's why out of the box they have egg-shaped cylinders. They no doubt compensate with wider clearances and for that reason I expect to dial in the bores to the low-side of their clearance numbers or use whatever the manufacturers of the pistons I use ultimately specify. MaxSil recommends 0.0015 (1.5mil). That's pretty damn tight.

Bottom End

Due to the likelihood of egg shaped bores I am expecting to bore the block to some degree.

Unless I find a better deal I am currently planning to go with MaxSil pistons and bore 20 over since they appear available only in 20 over sizes. These are 13% silicon and lighter than factory pistons, similar to the Metric Mechanic offering. The MM pistons have the advantage of hard anodizing but they are not available in 84mm (or oversize equivalents). MaxSil are roughly 60% the cost of BMW OE, which run $350+ a piston now. They also come with oversize wrist pins that should allow honing to match my (likely worn) stock rods. The ideal spec for wrist pin to rod clearance generally appears to be 4-5 ten thousandths (0.0004 to 0.0005 inches) so that is what I'll ask the machinist to achieve unless, of course, his experience dictates otherwise.

While researching boring and honing I read a bunch about the Sunnen SV10 honing machine. It's fully computer controlled and uses diamond cutters, which results in a much more consistent hone from cylinder to cylinder as compared to traditional vitrified abrasive stones. The problem is I have not found a shop within driving distance (yet) that has one of these machines. Most shops seem to still be using the old gear with traditional stones. The machinists who use the SV10 say it's "transformational", in that they can set it and forget it, and it is much more difficult to get the same consistent hone with the old fashioned machines.

Despite reading how well the cast iron blocks typically hold up I'm planning to mill the block simply to ensure a perfectly flat surface. Based on what I've read I shouldn't expect to cut deeper than 2-3 mil to clean it up. Flatness is not that critical with the OE gasket (as opposed to MLS) but it's fair to say it would be foolish to rebuild an engine to this extent and skip this step.

I'm still not sure what rod to select, if any. Many people refurb the stock rods with good results. I may be able to do the same but I'd like a lighter rod if possible and do plan to avoid anything of Chinese origin. I did confirm that M52 and S52 rods are the same (135mm) and with so many more people building S52's (or converting M52 blocks to S52) I will have my pick of rods. I also read a few accounts of people who have pulled stock rods with high mileage and found little to no wear, which provides some confidence that my rods will be reusable should I wish to keep costs down.

Obviously all bearings will be replaced with new. I learned that BMW has basically three color codes for the cranks and those match the bearings. One performance shop indicated that they typically see more wear on the front-most bearings (near cylinder 1) because the oil pump chain places additional forces on the crank in that location. However, they noted that the bearing clearances even on high mileage examples are remarkably consistent on these engines. So after I do the required cleanup of the crank journals I'm expecting to get a single set of bearings matching my crank and then purchase individual bearings to tighten up the front end of the crank if the wear in that area is inconsistent with the remaining journals. Naturally, I will be using a combination of measurements (via bore gauges and micrometers) and plastiguage to ensure proper clearances during the teardown and assembly processes.

Speaking of the oil pump, everyone recommends a new OE pump in this situation. One guy recommended using the chain designed for the S54, which is apparently better quality and has less slop out of the box than the equivalent M52 part, which is coincidentally the same as the S52 part. Of course, everyone also recommends using a drilled oil pump sprocket nut and some safety wire to eliminate any chance of the nut backing off. This problem appears to be mostly confined to cars that see track duty, but I am curious as to what I'll find when I pull the engine. Fortunately Turner and others sell these nuts, as they are a pain in the ass to drill without a fixture.

Someone on the forums suggested buying the reinforced oil pump pickup tube they described as originally designed for the 2.8L Z3. Turner lists this as part 11411703930. Realoem tied to my VIN indicates 11411730465 should be installed on my M52. It also confirms the 465 part is the older of the two as it is shown going into service in 1989 vs 1992, but curiously, both parts were apparently applicable to the E36 for the entire production run of the car. Thinking this was perhaps optionally installed on some subset of the E36 I checked the M3 (S52) and found it used the same 465 part listed for the M52, at least with respect to the production date of my car (1/98).

In any case, the pickup tube is a bolt-on upgrade and a relatively inexpensive one that that, so the plan is to examine my part, compare it to the new one and install it if necessary. The reinforcement requires removal of some of the mains bolts so an overhaul is the ideal time for the swap. My guess is this upgrade is probably only required on vehicles that spend a lot of time on the track but the effects of a failure of the pickup would be just as devastating on the street so I'll call this cheap insurance.

The OE main bolts have been used in applications exceeding 500HP so they will be adequate for my application obviously. The disadvantage in using main studs is that they extend higher than the windage tray so it would have to be cut. I don't see any point to spending the extra money and hacking up my tray so I will be using bolts (BMW or ARP, whichever is stronger and less expensive, if that's possible).

I am planning to replace the timing chains, guides and tensioners with OE simply because it's time.

Head and Gasket

Research revealed that the service limit on the head is 0.3mm (11.8mil). As I have never overheated my head I'm expecting to remove no more than 4-6 mil to correct it though I obviously won't know how much until it's done. I am planning to request a surface finish (Ra in micro-inches) of around 20. Only MLS gaskets require <20. I'm not sure what the factory spec is. Someone else reminded me that the timing cover must be milled along with the block so I'll have re-fasten that to the block when I provide it to the machinist.

I am convinced I will use the OE composite head gasket mostly because it's cheap ($50) and will obviously handle stock power. The newest BMWs use MLS (Multi-Layer Steel) gaskets because of forced induction, but this is not necessary on the M52 / S52. The OE gaskets are available in a 0.3mm (11.8mil) oversize. I may need to use that to compensate for the material removed from the head and block, as well as to provide a bit of a cushion with respect to compression ratio, since that will increase with the 20 over bore...though I haven't calculated yet how much.

I will be using head bolts as opposed to aftermarket studs. Everyone talks about studs being better, and they are. They allow for a more accurate torque because the stud and nut are torqued separately, but they make R&R'ing the head in the car more difficult, as the head can't be pulled sideways...it has to go straight up and over the studs. And as anyone who's done plugs on these cars knows, there's limited clearance in the back near cylinder 6.

Valve Train

My tech told me if there is any part of this engine that is guaranteed to be completely tired and worthy of a complete re-manufacturing process at 265K it's the valve train. I am therefore planning a full set of valves, springs, caps, retainers and seals. Supertech is one popular valve manufacturer. Normally I'd want to keep things simple and go with BMW parts but BMW charges over $100/valve. Supertech sells inconel valves or stainless with a black nitride treatment. The inconel variants have a higher temperature tolerance (1600 vs 1460F, or equivalent to 2200 and 1900 EGT respectively) and are only necessary for the exhaust position. The difference in price between alloys is not that bad, actually: $24 for black nitride stainless and $38 for inconel. Times 24 of course.

My tech said that BMW has a very imprecise measurement for valve tilt (a measure of valve guide wear) and this process has been screwing dealers -- the reps tell the dealers to send back heads with X amount of valve tilt, then the heads get back to the BMW repair facility and they find them within spec, so they bill the dealers thousands. My tech said that when they had a Cadillac franchise GM had a test involving a calibrated weight tugging on the valve stem. BMW apparently just tells their techs to "push on the valve and see what happens". How precise!

My technician suggested that if valve guides are indeed out of spec (whatever that means given their measurement technique) BMW typically reams the guides and installs valves with oversized stems rather than changing the guides. It turns out BMW offers +0.1mm and +0.21mm oversize stems with either standard or +0.5mm oversize heads, as well as oversize (+0.4mm) seats, while Supertech effectively offers only standard stems and +1mm oversize heads. Well, in full disclosure Supertech does offer a slightly oversized stem (+0.01mm or 0.4mil) but I'm not sure that would do anything but make a sloppy guide slightly less sloppy.

Interestingly, I read an account on the forums in which someone using the Supertech +1mm heads bent a couple valves during his initial dyno runs. He did not indicate that he had exceeded redline but did say he was using the stock pistons so I must assume this was a simple case of failing to accommodate the larger valves by either milling the piston reliefs or selecting an aftermarket piston with sufficiently large reliefs. This suggests rather strongly that exceeding 0.5mm heads with stock pistons requires extra work that I would prefer to avoid if at all possible. The question then is whether that work would exceed the rather high cost of a full set of BMW valves ($2500) that I know will work out of the box with the stock or stock-equivalent pistons.

I am considering replacing the lifters (Item 10). If there is no obvious damage to the lifter body (particularly the surface that interfaces with the cam) the core of the lifter can be removed from the body and both cleaned up and reinstalled. However, someone on the forums suggested that the tip of the lifter core wears to the point that after 150K miles or so it does not mate properly with the valve stem and so must be replaced. New whole lifters (Part# 11321748884) are $33 (~$792 a set) but the German OEM (INA) appears to provide replacement lifter cores for $12.50 ($300 a set). Assuming my lifter bodies are in good shape I'll likely go with the latter option.

The Vanos unit will be rebuilt of course, probably incorporating the Dr Vanos viton seals. One guy recommended buying their modified 16mm socket but he didn't say why. I have to re-read that installation process to figure it out if it's required for my application and/or worth the expense.

I'm reasonably confident my tech would let me borrow the expen$ive factory cam installation tools but many people R&R the cams using the "quarter turn" technique which involves clocking the cam properly, removing one of the caps entirely, and then very slowly removing the remaining nuts. Installation is the reverse.


I'm sticking with the M52 manifold due to OBD II compatibility.

All vacuum and vent hoses going to the manifold will be replaced. Fuel and vent hoses are obviously available from BMW but at what I consider high cost. I found Wurth (see online shop) sells the same quality fuel hose for a fraction of the price per foot but their minimum purchase is significantly higher, meaning the total cost would be a lot higher than buying the exact quantity required from BMW unless I wanted to sell the remainder. I don't want to be in the business of selling auto parts so I may default to BMW parts and just tighten my sphincter a bit before I pay the bill.

I'll be sending the injectors out for cleaning and balancing, probably to Marren Fuel Injection in CT. I was planning on using them years ago but never got around to it. Since it takes a few days to turn those around this is clearly the time to do that work.

M2 In Person

(Image: Perspective on the new BMW M2)

This is kind of old news at this point, but the M2 has been released. I managed to see one up close at the dealer for the first time this week and based on my initial impressions I must admit it's one of those cars that doesn't photograph well. It looks a lot better in person.

Standing alongside it I found I liked the overall size -- it was very "E46ish". The contours of the body side panels and doors were particularly attractive, especially as they related to the pronounced wheel arches, though the execution of the arches leaves a bit to be desired, at least compared to the 1M. Turns out the designers themselves weren't happy with them either but they admitted the bean counters tied their hands (on a M car, really?) Thankfully the M2, along with its parent 2 series vehicles, dispenses with the stupid melting door feature that plagued the entire 1 series.

The rear is probably the ugliest part of the design in my opinion. I find the vertical reflectors (obviously designed to break up the monotony of that big fat ass) particularly annoying and reminiscent of the Queen Family Truckster school of automotive design. The front is typical modern BMW -- which is to say -- hard edges and facets that serve little purpose other than aggression for aggression's sake. Hey BMW DesignWorks -- understated design language -- do you speak it?

There are two severe technical problems with this car in my opinion:

  1. Rev matching is on unless you turn all the nannies off. This is brain-damaged beyond belief. BMW needs to seek medical assistance for this obvious case of cranial-rectal inversion. Why the hell is there no button or other software option to simply to turn rev-matching off and leave all the nannies on? I just don't get it. I'm used to driving cars without nannies so I'd probably just turn everything off, but then why integrate (and pay for) systems I'm not going to use?

  2. The steering has no feel. Everyone is saying this -- even the apologists who take press cars for a spin and actually want to get a call back for the next new car BMW releases. I don't give a shit about gas mileage, or at least the degree to which electric steering improves it. Make it an option if you have to appease the libtards who are hell bent on making life suck for us all until the planet is pristine and our farts smell of roses, but I want my fucking hydraulic steering back!

Speaking with my technician we shared a frustration with how modern cars are built and behave. I asked "if everything new sucks, where do I go from here?" I guess the answer is the same as it has been for some time -- rebuild my 20 year old BMW, which is more of a BMW and closer to a true M car than anything BMW currently ships.