to those with aux water temp gauge - cluster vs aux readings??

[Jaker]

I'm running 5W40 Driven DT40 synthetic oil, and my lowest hot idle pressure is about 16-17psi. My pump is the Z3 aluminum block single Vanos pump (it's a little different externally, but the internals are the same). You could also bump up your idle a bit. Mine's set at 900 rpm to stave off the Getrag gear rattle.

I rebuilt the motor about 20,000 miles ago, and it gets beat on pretty hard - 7,800 rev limit in 1st and 2nd. I think if you're concerned about your hot idle pressures, and not already using a good synthetic, it might help.

[Sh3rpak!ng]

Engine was recently rebuilt by a highly reputable local machine shop to stock specs (hone, rings, bearings, valves). I'm at about 6,000km since the rebuild. Did not replace the pump which has roughly 150,000km. Nut is secured. Pressure hits about 55-60psi above ~3500rpm when hot.

My new gauges actually led me to finding a voltage issue. Started getting fluctuations after a track day this weekend with it dropping to 12.5 at times from 14. Intermittent fault with no cel and barely visible battery light flicker at some points. Suspected brushes but found both bearings very loose which killed the brushes from shaft wobble. On pulling the belt to get it out also noted Graf pump bearings had play and trickled coolant when wiggled. Only 30,000km on both of these! Talk about piss poor lifespan... glad I noticed the voltage dips early, either of these could have left me stranded.

Should I swap my 80a to a 140 while I'm at it? Car is fully loaded but stock electrically (16" pusher fan, heated seats, mild stereo never cranked, no ac, deleting ps this week).

Nah, no need for the 140. And my hot idle oil pressure is about the same after a full rebuild. I changed to a better condition pump after worrying about low idle oil pressure and finding some scoring in mine, it helped a bit, but its really nbd as long as pressure under load is good.

[Varinn]

Engine was recently rebuilt by a highly reputable local machine shop to stock specs (hone, rings, bearings, valves). I'm at about 6,000km since the rebuild. Did not replace the pump which has roughly 150,000km. Nut is secured. Pressure hits about 55-60psi above ~3500rpm when hot.

My new gauges actually led me to finding a voltage issue. Started getting fluctuations after a track day this weekend with it dropping to 12.5 at times from 14. Intermittent fault with no cel and barely visible battery light flicker at some points. Suspected brushes but found both bearings very loose which killed the brushes from shaft wobble. On pulling the belt to get it out also noted Graf pump bearings had play and trickled coolant when wiggled. Only 30,000km on both of these! Talk about piss poor lifespan... glad I noticed the voltage dips early, either of these could have left me stranded.

Should I swap my 80a to a 140 while I'm at it? Car is fully loaded but stock electrically (16" pusher fan, heated seats, mild stereo never cranked, no ac, deleting ps this week).

[JRKOUPE]

yup..

hot idle can be like 8-12 ish

kinda common...



as asked, miles?

[Sh3rpak!ng]

Only downside is now I'm very aware of how the engine is behaving. I'm finding that the stock 5w40 at cold start temps (+5c ambient) is about 50-60psi at idle, it drops progressively and hovers around 12psi idle when the oil gets hot (100 celsius). In stop and go traffic my pressure light flickers off and on somewhat frequently but I've replaced the oem switch with a double pole VDO that has a 10psi warning contact. I seem to never drop below 8-9 psi by the gauge reading.

I wouldn't be worried about those hot idling pressures... pretty normal for an *old* S/M5X with many *worn* surfaces. What's most important is your oil pressure under power. How many miles on it?

[Varinn]

what engine????....3.2 s52?


and yes..w/ gaUGES U WILL BECOME HYPERAWARE OF ENGINE STATE OF HEALTH..LOL...youll get over it


oops sorry bout caps

Right, yeah car has an S52B32 in it. OBD2 with m50 manifold.

[JRKOUPE]

what engine????....3.2 s52?


and yes..w/ gaUGES U WILL BECOME HYPERAWARE OF ENGINE STATE OF HEALTH..LOL...youll get over it


oops sorry bout caps

[Varinn]

I ended up running a 10gauge from the positive post to a distribution block/relay under the dash then 3 separate 14gauge feeds to the gauges and a 14ga ground from each gauges to a ring terminal on the chassis under the dash. 20 gauge wire is running the 3 bulbs in parallel and 20 gauge is also used on each sensor, everything so far is rock solid and appears very accurate.

Only downside is now I'm very aware of how the engine is behaving. I'm finding that the stock 5w40 at cold start temps (+5c ambient) is about 50-60psi at idle, it drops progressively and hovers around 12psi idle when the oil gets hot (100 celsius). In stop and go traffic my pressure light flickers off and on somewhat frequently but I've replaced the oem switch with a double pole VDO that has a 10psi warning contact. I seem to never drop below 8-9 psi by the gauge reading.

I'm thinking it's worth switching to something more like a 5w50 or 10w50 oil to try and bring my hot pressures up some without effecting cold much.

[Sh3rpak!ng]

Pretty sure vdo or whatever gauge manufacturer specs that out in the installation instructions. I'd follow their requirement.

[CorvallisBMW]

I think you could use 20AWG for the signal, backlights, and +12VDC, but VDO recommends at least 14AWG for the ground wires.

[Varinn]

Bump from the dead!

Does anyone have any input on what size wire needs to be run between the gauge and the sender? Could I get away with 20awg between the two and doing something like the distribution block with fat wires for the + and - part of the gauge circuit?

[CorvallisBMW]

Nice work! Yes, gauges like these are very susceptible to errant power from either wires that are too small or wires that feed other sources. I did the same thing you did with a power distribution block and 14awg wires for power and ground; mine are dead accurate!

[Sh3rpak!ng]

FIXED :D

So I was very stupid. I had chained all of the gauges onto the same 20awg wire. So there was a single 20awg wire for power, and a single 20awg wire for ground for all three of them. Also, I tapped the power supply to the radio to supply power/ground which I also tapped to hardwire a phone charger my god I feel stupid. I have NO idea what I was thinking. That kind of work is not even close to my usual standards...

Anyway, I have been wanting to clean up and organize the behind dashboard/under cluster/steering column wiring for a long time since the PO hacked it all up to install an alarm.

Solution: I ran a large gauge power line straight from the under hood power terminal which split to 2 12awg wires into 2 80amp relays (yea I know way overkill) which feed a 10 slot fused power distribution block. The relays are switched from ignition power (tapped a larger gauge purple/white wire which came straight from the ignition cylinder). I also added a ground distribution block which is supplied with 2 12awg wires from a factory ground near the top of the pedals. Each gauge is now individually wired with a 14awg ground and 14awg power and fused with 2 amp fuses. Additionally, I got a new water temp gauge just in case it was faulty since I didn't want to have to take anything apart again (I returned the old one via amazon).

I am now showing a solid 180-190 during normal conditions and haven't seen it pass 195 :D :D :D

Power distribution block makes it so much easier to add auxiliary items. I already wired up my radar detector, hardwired my usb phone charger and a volt meter

[Sh3rpak!ng]

I DO love my level sensor on the tank-

when the heater hose bypass popped off,
the housing temps DROPPED- so I looked over, the
level sensor was on (DOH!),
I braked- and the braking
sloshed coolant over the bulb,
causing it to spike up to about 240.

Which was where my heart rate was as I switched off...

I find that the housing location's pretty sensitive- I can watch
temps overshoot in warmup, rise slightly when drafting, overcool just
a touch afterwards- signs of an ever- so- slightly sticky t- stat...

t

So you have your temp sender on the thermostat housing on the m20?

Ugh I don't know what to do.

One thing I am sure of is that this will drive me crazy until I find a suitable solution :hitler::hitler::hitler:

[TobyB]

we kept racing for 2 laps on no coolant and the race was over.

I DO love my level sensor on the tank-

when the heater hose bypass popped off,
the housing temps DROPPED- so I looked over, the
level sensor was on (DOH!),
I braked- and the braking
sloshed coolant over the bulb,
causing it to spike up to about 240.

Which was where my heart rate was as I switched off...

I find that the housing location's pretty sensitive- I can watch
temps overshoot in warmup, rise slightly when drafting, overcool just
a touch afterwards- signs of an ever- so- slightly sticky t- stat...

t