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Friday, September 22, 2023

Doug's Domain

Doug Vetter, ATP/CFI

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Saturday, July 15, 2017

Another Parts Order

This week I purchased the remaining items from BMW I feel comfortable purchasing prior to the pull. The most expensive item in this order was the oil pump. Two weeks ago I was quoted $383 retail ($255 my cost). Unfortunately, in that time BMW raised the price of the pump to over $500 retail with a dealer cost of $323. My parts rep felt bad but could not sell me the pump for lower than cost so he sold it for a dollar more. He further offered to make up the difference to the original quote but there wasn't enough margin in the other small items I purchased at the time so he said he'd make it up to me on future orders.

If you're wondering why BMW would increase the cost of the oil pump so much it probably has to do with the fact that they are no longer collecting cores. The initial quote indicated that the core was required but when I finally purchased the part I was told that was no longer the case. Given how many engines use this particular pump I would like to think that BMW has simply decided to sell new units outright and avoid dealing with the overhaul process (perhaps because the quality of the cores has dropped below remanufacturing standards) but if history is any judge this is more likely a prelude to selling the remaining inventory and transitioning the part to ENDED status.

Transmission Cooling System, Mounts, and Solenoids

(Image: New automatic transmission cooler lines)

One essential step in the installation of a remanufactured transmission is to ensure that both the transmission cooler and the lines leading to it are in good condition and flushed free of any old fluid and contaminants. Toward that end, this week I analyzed whether to flush or replace the transmission cooler and pipes.

I last inspected the transmission cooler back in 2013 while I replaced the radiator. Although it was visibly dirty I didn't see any obvious corrosion or other defects, which is why I returned it to service. Considering the price ($370 with my discount for OE, $250 aftermarket via Turner) and the fact that swapping it would require pulling the radiator (yet more work I don't need right now) I'm planning to flush it in place and return it to service.

The lines are a different story. If they were 100% metal I'd flush and return them to service based on condition, but they integrate a flexible rubber portion and I haven't seen a 20 year old rubber line I'd trust. Although the transmission is instrumented to the point that an over-temperature condition would be reported in the event the lines internally swell and cut off flow with the cooler I decided to replace the lines now as doing the work later would be considerably more complicated. Browsing Pelican Parts I saw two different brands of aftermarket lines, but because my discount more or less wiped out the price differential I purchased the OE parts ($94/$122) to ensure quality / fitment and take advantage of the 2 year warranty. Of course, I purchased four new o-rings for the lines as the originals are not to be trusted.

Knowing that the transmission mounts are original I decided to buy new mounts. The only thing interesting to report about these is that the ETK part description says "mount kit", implying a set of two but then suggests the vehicle needs two of that part number. My parts rep confirmed that the kit is a set of two mounts, so I only needed one kit at $16.

I considered buying new solenoids through BMW but quickly learned two of the units were no longer available. It's probably just as well considering that the EPC solenoid (responsible for setting line pressure) was last listed in the ETK for $450 and the other solenoids were more reasonably priced but still over $100 each with my discount. This forced me to look to the aftermarket for these items. As it turns out there are two versions of the EPC solenoid available in the aftermarket -- one is made by Borg Warner and the other by Bosch. The Borg Warner comes wrapped in a black cover, while the Bosch unit lacks a cover and is hence advertised as the "silver can". I learned from several unrelated sources that use of the Borg Warner unit in a BMW will result in transmission fault codes so I began looking for a supplier for the Bosch part.

I eventually came across a company selling an entire set of NOS OEM solenoids specific to the BMW application of the 4L30E, including the Bosch EPC solenoid. According to the supplier these were obtained directly from the GM factory in France -- the same facility, incidentally, that originally assembled the units for BMW. While I'll reserve judgment until the transmission has been road tested, if these units do work as advertised I'll consider this one of the better deals I've found in this project. I should point out, by the way, that I will be keeping the original solenoids removed from the unit so I can reinstall them in the event the new OEM solenoids cause problems.

Lifting Hardware Order

In preparation for lifting the engine block with the newly acquired AFF load leveler I used my calipers to measure the inside dimensions of the links in the provided chain. With a bit over 9mm to spare, I decided to acquire some high strength M8 bolts and nuts, as well as some oversize washers necessary to secure the chain to the lifting points on the engine.

In this configuration the bolts are in shear. This requires careful hardware selection because the threads further reduce the effective diameter and hence the shear strength of the bolt. In addition, the thread valleys can serve as stress risers and precipitate a failure under load. As dropping this block would very likely result in severe damage to both the block and my brother's garage floor, I decided that I would acquire bolts with a partially threaded shank so that the chain links are in direct contact with the unthreaded portion (or as much of it as possible). When the bolts I selected (50mm in length, roughly half threaded) came in I test fit them by passing the bolt through two links of chain. Although I probably should have bought bolts in a longer length I think these will do. I guess I'll soon find out.

For those that care about this sort of thing, metric grade 10.9 bolts (similar to SAE grade 8) are typically rated to 150000 PSI. For a M8 bolt this typically results in a tensional strength of over 8000 lbs and shear strength of nearly 7000 pounds. This far exceeds the rated lifting capacity of all my equipment, to say nothing of the weight of the engine fully dressed, so if anything fails it's fair to say it won't be the bolts.

Lifter Precharging

I picked up a couple tips recently while watching a video about M50 cam and lifter replacement. The author was using INA lifters and said that he had communicated with INA at one point to verify the break-in procedure. It turns out that there is nothing special to this process -- the engine should be started and idled for one minute. If after one minute there is any persistent valve tap the engine should be revved to between 2000 and 3000 RPM (presumably varying the RPM slowly between those limits) for 4 minutes. The engine should then be returned to idle. If the tapping persists then the procedure may be repeated up to four additional times before declaring that a lifter has collapsed. It should come as no surprise that this matches the BMW procedure as well.

To avoid valve tap it is helpful to precharge the lifters before they are installed. This can be done by compressing the pistons repeatedly with the lifter submerged in oil or by dropping the lifters into a small vacuum chamber filled with oil to draw out the air. I have decided to try the vacuum chamber approach and toward that end have purchased a $25 hand-operated vacuum pump kit. Although it is possible that the lifters will continue to bleed down in the days prior to installation and some valve tap will be inevitable on the first start, I have always been impressed by this engine's ability to tolerate long periods of inactivity. I have often started the engine after 3-4 weeks and been greeted with a silent valve train (at least until very recently), so I'm hoping this precharging effort will reduce the chance of valve tap during the initial start and possibly expose any defective lifters before they are installed.

If the lifters are precharged the lifter pistons will be fully extended and rigid, i.e. they will not compress -- at least at first. Once the lifters and cams are installed this will cause all the valves to open to some degree. For this reason it is REQUIRED to ensure all the pistons are below TDC before the cams are installed. Furthermore, it is necessary to wait at least 30 minutes at room temperature (longer at lower temperatures) to ensure the lifters bleed down and all the valves close against their seats prior to engine start, but as my engine will likely sit for days prior to installation this limitation will not be a factor in my build.

While doing additional research on Bimmerforums I discovered another US-based manufacturer for M52 lifters. However, I found several accounts of owners complaining about the noise these units produce even after several break-in procedures. This is obviously not just an issue of noise -- excessive clearance between the lifter piston and the top of the valve that causes the tap can ultimately cause damage to both parts. Several people recommended the afflicted owners replace the problem lifters with INA so I think it's safe to say I've selected the correct parts.

Next Up: Work Begins

The vehicle is scheduled to go to my tech on Monday. If all goes well I should have the car back (in pieces) by the middle of the week, at which point I can start the rebuild process.