4-in-1 Digital Gauge Question

[Beetz]

Hi all,

I am considering installing this gauge system into my 91 318is:

https://www.ebay.com/itm/BMW-E30-E24...EAAOSwhe9eOdQw

Has anyone installed this kit? If so, would you recommend it?

I plan on installing the oil temp sender on the front of the oil filter housing in place of the M12x1.5 plug. I believe I can install the oil pressure sender on the back of the head in place of another M12x1.5 plug; could anyone verify installing the pressure sender on the back of the head?

What is the best location for the coolant temp sensor? Would replacing the coolant drain plug with a M12x1.5 sender be sufficient? (I know this car has a coolant temp gauge in the dash, I would just like to know an actual number and also don't really care about ambient temperature outside the car) If this is not an option, what is the next recommended installation for the sender; drill and tap thermostat housing? add a section of hose designed to hold a sender?

Any advice on this would be greatly appreciated! I've wanted oil temp and pressure data for some time and this seems like an affordable option with very minimal interior modification.

[bmwman91]

If the senders have the same thread size as the plugs you mention then that much is fine. There really are no other options as far as locations, unless you want to start cutting hoses or messing with tee-fittings and stuff. Fitting the oil pressure sender to the back of the head might be sort of tight against the firewall, and the reading there is likely going to be lower than at the filter housing, but the value varies across the system anyway so it's sort of relative.

Are you building a track car? If this is just a street car then this stuff is sort of a bit of work for minimal useful information. It's fun to have the measurements and all, but beyond that I am not sure how much value it provides (to each their own, of course).

[Beetz]

I have also cleaned up the mess-under-the-intake on this car, would it be better to try and put the coolant sender there somehow? Would putting one in the drainplug be an issue as its close to the exhaust? Also, I believe I posted the wrong size plug for the drain plug. It should be M14x1.5 I believe.

For the oil senders, would you recommend switching them? Putting the oil pressure sender in the blank plug on the filter housing and the temp sender on the back of the head? This would eliminate the space issue on the back of the head, but could also introduce a clearance issue with the belts and things by the oil filter housing.

This is a street car that is driven spiritedly on mountain roads. The main reasons for wanting to install this is, it would be fun and interesting to know, and also the car has 265,XXX miles, so I would like to know immediately if something is going wrong. It is also a relatively inexpensive mod that is fun, and also I can attempt to "justify" it by telling myself it will help the life of this engine ( lol )

[bmwman91]

Yeah, tapping into the unused (after the MUTI cleanup) barb coming from the head is a decent option. Maybe you could rig something up with hose barbs and pipe fittings. You'd want it to connect to the nearby unused barb on the plastic water pipe so that coolant was flowing through. That is a lot more work though, and the block drain is probably your easiest bet overall. The nearby exhaust pipes might be a little bit of an issue for any plastic stuff, so you are correct about it possibly being an issue. I would not worry so much about it melting, as just getting brittle and falling to pieces after some time.

And yes, putting the oil pressure sensor on the filter housing might be better. If it seems to be in the way of the belts maybe you could extend it out with an additional fitting. Either that, or if there is room and you can find an M12 tee fitting, you could have the sensor and stock pressure switch all together on the back of the filter housing.

[Beetz]

Sounds good on the coolant sender location! After a bit of looking around, there seem to be a few inline 5/8" hose adapters that can take 1/8npt senders: https://www.glowshiftdirect.com/16mm...se-attachment/ This would allow me to install the sender inline between the block and the plastic pipe; would you recommend using an adapter like this?

As for oil temp/pressure, the kit does come with a T fitting, allowing the pressure sender to be installed on the stock sender side of the housing. Are those fittings known for being failure spots? The last thing I want to do is add a known source of failure. Would perhaps something along these lines be a better option: http://www.hardmotorsport.com/rally-...adaptor-block/ or https://www.bimmerworld.com/Gauges-D...MaAvYxEALw_wcB ? More expensive, but not in comparison to a catastrophic oil failure.

Thanks for all your help on this! My initial goal was to use no adapters so as to not increase the number of failure locations, but that is seeming to hard to do; the area behind the head is definitely tight, and the area in front of the oil filter housing is quite close to the alt belt...

[bmwman91]

Honestly, whatever fits is probably fine. The coolant system is less than 20PSI, and the oil system is probably no more than ~80PSI at redline. Those are low pressure in the grand scheme of things. If the fittings are metal, I find it pretty unlikely that there will be any sort of failure where you lose all of your oil or coolant...the most likely complication is an annoying leak that slowly makes a mess on your engine. Even that can be avoided by careful assembly and the use of crush washers where applicable.

[Beetz]

Gotcha, that all makes sense to me!

Would it be possible to mount the oil pressure sender in the location of the stock sensor that talks to the light in the dash? Would it physically fit and also function correctly in a horizontal position? If I could put the pressure sender there, I believe I can cut the original connector off and then wire it to the WK post on the new sender. This would theoretically give me a functioning dash light, and also eliminate the use of a tee fitting; I would however still need a bushing style adapter to get the 1/8npt sender to mount into the M12x1.5 hole where the dash light sender is currently. Any thoughts on this going route?

[bmwman91]

I'd avoid hacking up the factory harness. It's a lot harder to undo that than it is to move fittings and whatnot. The better solution is to make the non-OEM thing fit somewhere withoutmaking permanent changes to the original equipment. Having a functional oil pressure light is pretty important, as infrequent as it may be that it is needed.

[Beetz]

That totally makes sense. I may try and make a little connector that can connect the factory harness to the WK post on the pressure sender then; we'll see how that goes! Thanks so much for all the help, I think that answers all my questions for now! I will post updates once I have them, and document the process of installing this 4in1 gauge setup on an M42.

[bmwman91]

Sounds good.

For reference, the factory oil pressure sender is just a switch. It is normally closed, connecting the light in the cluster to ground, and once oil pressure is above ~1.5PSI it will open, thereby breaking the light's circuit. Your oil pressure sensor is probably going to have some sort of voltage output, or maybe it is resistive, but either way it won't quite be what you want to maintain oil light operation.