M40 to M42 Is engine

[DaveMcleod88]

Hi all a previous owner of my E30 fitted an IS engine to it from the standard 1.8 engine my only problem with it is the temp gauge doesn't work, when u put ignition on the needle goes straight up to red line once started it drops and doesn't move at all.

Is this a common thing to happen with the conversion or does it sound like something else

I will change the temp sensor to see if that does it the car has been like this for the last 25k mile and has an electric fan installed that's manually operated via 2 switches inside fast for traffic jams and slow for slow moving traffic has always kept the engine happy but I really want this sorted to make sure of no nasty surprises

Is the only sensor on the engine? The radiator fitted to this doesn't look to be standard any maybe out of a E36 put I believe sensors on radiators are only fan switch's not temperature gauges for the dash

[jmc330i]

Was the engine from an E36? They use a different temp sender for the guage, so you would need an E30 sender for the gauge to work.

[Brianmoooore]

E36 325i radiator is identical to an E30 318iS radiator.
If it's an iS engine from an E30 that has been fitted, the gauge should work properly, since the sensor and wiring are identical.
If the engine came from an E36, then that will need an E30 sensor fitted to it.
Unscrew the C101 20 pin engine loom plug and socket (next to the fusebox), turn the ignition on and see what the gauge does.
I'd recommend retro fitting the correct mechanically driven fan as well. An electric one has no advantages over what BMW specified, and is far less reliable.

[Brianmoooore]

Was the engine from an E36? They use a different temp sender for the guage, so you would need an E30 sender for the gauge to work.

I'm fairly sure that, in itself, wouldn't make the gauge over read, so I think there's more to it than that

[DaveMcleod88]

Thanks hers a picture of the engine if it's any help to tell the difference between E30-36


As you can see the radiator is botched in, There is an IS at the local scrap yard will be taking the fixings to secure the radiator and viscous + Shroud at the weekend

[jmc330i]

The rad looks ok... the fan on the other hand That certainly needs sorting!

Was the engine from an E36? They use a different temp sender for the guage, so you would need an E30 sender for the gauge to work.

I'm fairly sure that, in itself, wouldn't make the gauge over read, so I think there's more to it than that

The OP said the needle goes to red when the ignition is on, but drops and doesnt move once started. I wouldnt call that over reading...
The needle on my S50 conversion did something strange for the first few start ups as I hadnt changed the sender, but to be honest as it was so long ago, I cant remember what the needle did. It was just an idea.

O/T - Brian, you have a PM when you get 5mins

[DaveMcleod88]

Going to give this a wee bump

So pulled the 2 coolant/temp sensors out a scrap E30 Is at the local scrappy and tried plugging them before fitting to see if the gauge flew up at ignition then back down once started and the same problem happened, When digging out the plugs I found that Sensor 6 Wasn't plugged in at all and when I put it back on the oil light now stays on and the gauge still doesn't work

Can anyone shed some light on what I can do here

Oh Radiator has been secured and awaiting a new viscous coming, Picked up a shroud and fan blades today but the viscous had no resistance so left it

[Willeh]

For reference, the breather hose being at the front of the cam cover rather than the rear says it's most likely an E30 engine, but I'm guessing they're interchangeable so it's not 100% confirmation.

[bake_e30]

I had this problem when I did my m40 to m42
Found out I had the oil pressure switch and temp sensor the wrong way around at the c101.
The oil light would get brighter as the car warmed up and the temp guage would hit full when the ignition was on.

[DaveMcleod88]

I had this problem when I did my m40 to m42
Found out I had the oil pressure switch and temp sensor the wrong way around at the c101.
The oil light would get brighter as the car warmed up and the temp guage would hit full when the ignition was on.

Haa this might actually be the problem as it did get brighter good stuff I'll look into the pins to swap them round thank you

[bake_e30]

I had this problem when I did my m40 to m42
Found out I had the oil pressure switch and temp sensor the wrong way around at the c101.
The oil light would get brighter as the car warmed up and the temp guage would hit full when the ignition was on.

Haa this might actually be the problem as it did get brighter good stuff I'll look into the pins to swap them round thank you

I might have had the plugs for the sensor's the wrong way around but I just swapped them at the plug because it was easier to get at

[DaveMcleod88]

I'll test for continuity between the plug and c101 to make sure there in the right position, I hope this is the problem and thank you for posting !

[Brianmoooore]

This theory fits exactly with your OP, so there's a good chance you're onto a winner.

[DaveMcleod88]

This theory fits exactly with your OP, so there's a good chance you're onto a winner.

I agree and thinking more into it with it shooting straight up to the red on ignition as would normal the oil light once started goes back into the cold as would the oil light go out so indeed sounds very promising

[DaveMcleod88]

Well swapped the wires around and hey presto! The gauge is now working as should. Thanks for the replies everyone now can safely keep an eye on the engine temp instead of running a noisey electric fan all the time

[rix313]

Looks to me like you need to shortern that rad top hose and probably the lower one too. will be doing you no favours having it kinked like it appears in the photo.