Finishing touches

It’s been quite the exciting year so far, at least for the car. I’m confident that the car will be roadworthy within the month. I’ve made some tremendous strides; gathering parts, new gaskets & seals on the B32, integrating Motronic 1.3, newer fuel injectors, WBO2, etc.. I’ve also managed to install the motor into the chassis.

So what’s left to do?

  1. Button up the cooling system. (Done 4/8/20)
  2. Swap the steel air filter assembly for a newer aluminum unit, install AFM and replace cracked hoses. (Done 4/8/20)
  3. Get the fuel system connected. (Done 4/11/20)
  4. Figure out what’s up with the EVAP system solenoid (4/11/20 – I plumbed it into a brake booster valve & taped it up – jury rig!).
  5. Get the upgraded coil installed & plug wires set up properly. (Done 4/11/20)
  6. Torque hub nut properly. (Done 4/11/20)
  7. Hook up the exhaust. (Done 4/11/20)
  8. Fill up the fluids; 15W50 synthetic & plain green temporary coolant. (Done 4/11/20)
  9. Clutch pedal is clicky, a little messed up. (Done 4/12/20)
  10. Bleed the upgraded front brakes. (Done 4/12/20; Easter Sunday)
  11. Hook up the battery, test for parasitic draws. (Done 4/18/20)
  12. CAR FINALLY STARTED! (Done 4/18/20)
  13. Install cheap/ugly digital media receiver ($20 Dual BT/USB/AUX from Walmart). Put the interior back together, including kick panels and center console. I ignored the door chime for the time being, since it’s annoying. (Done 4/19/20)
  14. Rewrap the tattered engine bay wiring harness, added some zipties. (Done 4/19/20)
  15. Washed the car, very thoroughly, noted leak at the base of the driver’s b-pillar. Plugged sunroof drains, ugh. (Done 4/26/20)
  16. Wideband O2 needs a proper wiring harness, instead of the hacked-together mess I made last year, I’ll have to figure that out. I’ve temporarily run the harness up through the gear shift into the center console. (Done 5/2/20)
  17. Change trans & diff lubes with RedLine MTL & 75w90 synthetic lubricants. (Done 5/2/20)
  18. Bleed the upgraded rear brakes. (Done 5/3/20)
  19. Bleed cooling system (Done 5/9/20)
  20. Re-wire the C103 connector. I like having an tachometer, the economy meter is also good fun. Why not? (Done 5/9/20)
  21. Crimp some scrap onto the exhaust so it doesn’t drop off the car. (Done 5/9/20)
  22. Figure out what’s up with the Auxiliary Fan. Low speed was fixed with a new relay. (Done 5/10/20). High speed fan from fuse 19? green/black wire to the high speed 210degF fanstat, black/green to the K6? relay, black/yellow to the fan’s red wire.
  23. Drive the darn thing! (Done 5/13/20)
  24. Rough running, it does rev nicely, really sweet high in the rev range, but idle is very rough. (Done 5/24/20)
  25. Figure out what the three three-pin connectors do on the E24 B35 wiring harness under the intake. Figure out how to integrate them with the E34 plenum since I have no other choice. There should be a fat battery positive from the battery, a smaller connection to the alternator (blue wire from C101 pin 1), and two oil sender wires (blue/violet C101 pin 2 and blue/white C101 pin 10).
  26. Fix the evap system, part 2. I managed to find the old mechanical evap valve in some E30 parts, so at least the boot is air-tight. The B34 uses a mechanical vac valve. The B35 uses an electronic one. How to merge these two into one?
  27. Coolant temp sensor? My guess is that the original part was this one, but it’s been replaced with this one.


  • Cooling system: Had a problem with the heater hose off the back of the block. The stock part was far too short?!? I managed to scrounge an S85 cooling hose from a large lot of parts I’d recently purchased. It needed to be shortened, but otherwise was a very suitable shape. I traded the newer spring type clamps for classic screw-style hose clamps; looks like it was meant to be there.
  • Air filter housing: The only AFM “elbow” hose that wasn’t cracked was from my 535i engine. Newer rubbers (with the exception of silicone & fluoroelastomers) are noticeably less durable than older parts, although they have gotten cheaper. I’d guess they must have used some truly obnoxious chemicals in the old formulae…if that’s true, a shorter lifetime is a worthwhile sacrifice.
  • Clutch: It worked but kept clicking in an annoyingly random fashion. Investigations determined that the return spring wasn’t seated properly. It’s a clever little setup with an over-centering spring, allowing adjustment of clutch pedal “weight”. I pulled it all apart to adjust & align the spring on its little perch properly.
  • Gearbox: Oddly, there was a small amount of water in the gearbox lube. WTH? I never took the car mudding, I swear! Worrisome development, to be continued… Update: the gearbox is improving. Originally, it was reluctant with R/1/2. After about ten easy miles it’s shifting very well, although it does still pop out of reverse half the time. Happily, there isn’t any nasty bearing noise, and the shift action is very good. The 265 has a legendary reputation for durability…why not test that out? I’m sure there’s still a bit of water left in there, but driving it around generates a lot of heat. The remaining water should evaporate fairly quickly. I’ll also be flushing it with new lube as time goes on. With a bit of luck and a few hundred easy miles the reverse pop-outs might fix themselves.
  • Rear brakes: There was quite a bit of loose rust plugging up my rear passenger bleeder valve (junkyard E32 740i upgrade!). Took a while to track that down & get it all cleared out. I should have rebuilt them, but I’m in a hurry to get this on the road…
  • Wideband O2 wiring: The proper wiring for the gauge is: red to +12VDC switched power, black to ground, white to NB O2 signal wire, blue is a serial output for standalone ECUs (not used here). The Bosch NB O2 harness in a BMW has four wires: black is sensor signal, grey is sensor ground and two white wires for the heater, non-polar.
  • E24 M30B35 harness: We’re missing the starter sub-harness. I’ve used an E34 version instead, and the connectors don’t mate up 100%. There is a spare 3-pin female plug. How will they mate up with the E34 plenum sub-harness in their purgatory under the intake manifold? Which one is the oil level sensor? Which is the alternator? What’s the third one for? Are they a combination plug? Lots of questions here, LOL.
  • Oil level sender has two functions as well. On the B35, there is a static and dynamic oil level function. The connector should have three connectors: blue/violet (static – to C101 pin 2), blue/white (dynamic – to C101 pin 10), brown (ground – engine block?). The oil level sender only has two connectors, is it grounded through the case?
  • Exhaust: Jury-rig the cracked center section so it doesn’t fall off the car, then get someone to weld the fragged junk together until I get something better. Old rubber hangars are beyond shot, new rubber hangars have arrived. I’d also like to restore the middle bracket; the center exhaust section hangs off the transmission tailcase. It’s NLA from BMW (No Longer Available), but I’m hoping a few rusted-out leftovers can be cobbled together into a workable substitute
  • Auxiliary cooling fan: , I noted that the fan is only powered on ACC. The A/C system will also switch the aux fan on at normal speed by jumping black/blue wire to the K1 relay, just as the fanstat does. A/C is protected by an inline diode upstream of the K1 relay, possibly mounted in the cabin somewhere. Normal speed can be triggered by either the A/C switch or the normal speed fanstat. Aux fan normal speed is powered from fuse 19; green/black wire to the low speed 190degC fanstat (lower location, white collar); black/blue to the K1 relay; black/blue to the aux resistor black wire thence to the fan itself.
  • Rough running: Turns out I had a bad spark plug and needed a valve adjustment. I had to think that one over, dig a little deeper, double-check what I’ve done so far. A leak-down test can test out a lot of potential causes at once. It’s best to pull all the plugs and check the valves before doing a leak-down or compression test. While I was doing this, an obvious problem jumped out at me – the #1 plug had a bent electrode! I’m guessing that happened when I (carelessly) tapped the head on the block once during assembly. Most of the valves were also too tight, so I re-adjusted them all. To finish up, I bent that plug electrode back into shape, cleaned & filed & checked the plug gaps, popped them all in after the valve adjustment and cleaned up. The car immediately started running FAR better. I’m still suspicious of a bent valve or timing issue. I didn’t get any results at all, 100% loss in the three cylinders I checked. I’m sure it’s user error, or potentially because the M30 has too much overlap at TDC. Regardless, I’m putting the leakdown test on the back burner.
  • Hacked up distributor: I suspect my hacked-in early M30 rotor arm –> late M30 distributor cap mod is causing some trouble. It’s a little ugly anyhow, I’d like it to be easy to fix in case of trouble. There are a few solutions; (1) Modify the later-style ‘wide’ cap to work with the early ‘tall’ rotor. Just takes some judicious grinding and drilling a deeper hole for the center carbon ‘button’ electrode. That’s because the later ‘wide’ cap has a deeper center pin to prevent installation with the ‘tall’ rotor. (2) Shorten the ‘tall’ early rotor to fit the late ‘wide’ cap…instead of grinding down the dist. cap center contact tower, just shorten the early rotor. I’m not 100% sure this can work since the arm has grounding tabs internally. (3) I’m guessing it’d also be pretty simple to make an early ‘skinny’ plug wire harness with the Motronic 1.3 cam position sender installed on the #6 wire.
  • Coolant temp sensors: So the idea is to have the DME sender match the motor & electronics. The temp gauge sender has to match the chassis. The plug changed, we’ll have to chase down some wires.
  • Here’s the RealOEM diagram for the late-production E24 chassis BMW. It mentions that there’s a dual switch (VDO Temperature sending unit/warning contact – 120CEL – 03/1987 – 12621716137). The E24 has a temp gauge sender, grounded to the motor, with two outputs: one to drive the gauge with an NTC (negative temp coefficient) sender, the other to light up an “overheating” idiot light in the gauge’s red zone with a switch. ETM states that the switch closes above 117degC/243degF precisely. With the M30B35, the NTC/sender side uses a brown/violet wire to the gauge, the warning contact/switch side uses a brown/yellow wire. Late production E24 apparently didn’t keep the warning contact/switch function.
  • The DME sensor has two part numbers listed: 13621709966 and 13621709967. They should both be the same, with blue connectors. That bit appears to be functional.
  • The B34 has three senders on the coolant neck. On the E24 B34 neck, the DME sender is furthest from the head, with a black connector. The middle position is the “Thermotime” (TT) controller, also a black connector but with dual spades, and nearest to the head is the temp gauge sender, usually with a white connector. There’s two different TT systems: an electrical sensor or a thermal vacuum switch. Both use different techniques to control the evap system, preventing it from opening when the engine is warming up (in open loop). Later B35 motors used a solenoid valve directly wired to the Motronic. I’m told that the B35 has two: the blue plug goes to the DME, the black one goes to the cluster. Link:

Edit; Bentley manual page 170- 4 and 5:1.. temperature gauge sender in thermostat housing2. engine coolant temperature sender ECT to DME3. EML coolant temperature sensorso where the hose is connected, first first one is 3, then 2, and 1. If you do not have EML, the one closes to the hose is item 2 for DME, and the one farest away is for the temp gauge.but realoem shows it a bit different…diagId=11_4616coolant temperature sensor wire colours1988 -1992 M30gauge sender: brown/violet-brown/yellowECT = DME: brown/red-brown/orangeEML sensor: brown/red-blue/violet12621710535 2 pin, [mm]:M 14 x 1,5, Nennspannung [V]:12 Widerstand/resistance [Ohm]:5000, 54413621709967 BOSCH Temperature Sensor – Coolant (20 deg. C / 2500 OHM) , 2-pin, M12 x 1,5