E30 318i: Correct Temperature Sensor fitted (Brown Plug) + wiring/loom issue

The temperature gauge in the dash has not worked since I bought the E30, which was a little worrying on my 250 mile drive home, but the car does not overheat. Oh, it has some issues with the cooling-system, like the heater-matrix pipes fitted incorrectly and an air-lock at the back of the head, but hey it doesn't overheat. Still though, I thought it best to get the bottom of the faulty temp. gauge for peace of mind, particularly with summer coming / just about here.

The M40 has two separate temperature sensors that are independent from one another. The temperature gauge works from the 'Brown plug' sensor to the rear of the head [right in pic]. The forward sensor is the 'Blue plug' [left in pic] and that connects only the DME (ECU) to tell the car if the engine is cool or warm to help with cold-start procedures. A single sensor cannot be used for both purposes on these older engines as the resistance value ranges required for each function differ, the DME being a digital circuit and the temp. gauge still working in analog. [You can read more about this on the E30 Zone Wiki HERE].

MULTIMETER TESTING:

The temp. sensors can be easily tested with a multimeter set to 20k ohms resistance. 

The Blue plug is a two-pin sensor, so test across both terminals with the multimeter and you are looking for a reading of 4-4.5k ohms for a working sensor. This sensor and plug can be accessed easily without removing any parts from the engine.

The Brown plug though will require removal of the lower inlet-manifold to access the sensor for testing or replacing. This is a single pin sensor, so place one probe of the meter to the terminal and the other to a ground-point in the engine bay or against the block/head. Expect a reading of between 1k and 1.5k ohms for a working sensor. To test the Brown plug sensor without removing any parts from the engine, you can apply the multimeter to Pin 4 of the C101 connector (main wiring loom plug in engine bay) which is easy enough to get at, or at Pin 26 of the blue connector to the right side of the instrument binnacle, though the binnacle will need removing to do this.

WRONG SENSOR / CONFUSING WIRING LOOM:

All M40 engine wiring looms use a single pin temp. sensor on the brown plug that earths through the engine block and have only a single wire in use leading to it. Some looms, using components destined for other BMW models, are known to have a second wire leading to the Brown plug temp. sensor which is redundant on the M40 motor, though this is rare and seen more often on 6-cyl. M20 looms. My car has one such loom, however and I realise that this is what has caused confusion in the past and led to the wrong sensor in fact being fitted...

Upon inspection, the rear temp. sensor fitted to my E30 is black, not brown and has two terminals. The second pin means that the sensor body earths back to the loom and not through the block so, if the redundant earth wire in my loom is not connected to a ground-point then the sensor was open circuit. I guessed that someone had ordered a second Blue plug sensor by mistake and fitted that, but it turns out the part number doesn't match and the sensor is for a completely different model engine entirely. The reading from the multimeter was over 11k ohms, something like 7.5 times what it should be! That sensor was never going to work with the E30 temp. gauge circuit whether it was earthed or not.

I ordered the correct single-pin sensor with the brown base from mr-wiper on eBay, who also supplied my Bosch spark-plugs. It was only £7.69 delivered. My temp. gauge now works, but this may also be due in part to removal of an air-lock at the back of the head due to a heater-matrix problem so coolant is now flowing properly round the area of the sensor. 

A BIT MORE ON WIRING LOOMS:

Brown / Violet, brown being the main colour, denotes that the power source provided from the temp. gauge circuit is earthing through this wire and does not need to be a closed circuit back to the gauge. The other wire is either not wired in to the loom or goes to a body-earth anyway, so earthing the sensor through the block will make no difference. This colour coding is the same for all wires in all BMW looms, I would imagine most cars are the same.

E46 Clubsport: Loss of coolant... split radiator!

The Clubsport is starting to become a bit 'whatever next' lately. Amidst the other post new year jobs I forgot to mention the coolant expansion-tank that sits next to the radiator had swelled and split down one side, so a new one was duly fitted.

Last week the sudden loss of coolant returned, with the puddle in the same place under the radiator, but no visible sign of a leak. Nath assumed it to be the radiator-cap, so we pressure tested it in work and it's fine. Then we pressurised the rest of the cooling system and this is what we found - the radiator has burst along the top. A new radiator is going straight in, but the fact remains that something is still pressurising the cooling system and needs to get sorted.

E46 Clubsport: Quick rev and exhaust burble...

Quick rev of the CS as we stave off real work by fiddling with Beemers. It finally has that proper vanos whoosh and exhaust note, though there is still a bit of a misfire / bogging down under acceleration and no fault codes are coming up on Autocom GDP, but DIS will find something and I will post the results. Shame, as this is delaying that front bumper splitter...

E46 Clubsport: Nathan's split rubber + other issues.

More big spending as the Clubsport gets back on the road with a new MOT, starting with 4 new Maxxis tyres for the refurbed split-rims. It's been running a bit rough, but as he started it for the first time in a month it ran a bit worse and began producing a lot of white / blue smoke from the exhaust. Fearing the head-gasket he started dismantling and found it was just one of the profile-gaskets in the rocker-cover [16 in the bottom diagram] was split and hadn't seated in the head properly the last time it was replaced and was allowing oil to spill down into the chamber and was causing the smoke. This, he assures us, is a common problem in 6-cylinder BMW petrols and had nothing to do with any 'engine-weld' products he may have also added. Never the less, with a new rubber-gasket the smoke has ceased. During the job he found the rubber intake hose was also split in two places, clearly contributing to the lack of smooth acceleration suffered since he got it, so he treated the 330 to a new one of these as well.

The MOT threw up borderline high emissions, which was waved, and both front lower ball-joints were knackered. These are usually replaced as a whole control-arm, so that's what was done and finally the Clubsport is back on the road, looking and sounding as it should with better pull and a really raspy vanos exhaust note. Next up comes replacing the lower bumper splitter sorely missing from the front end.

E46 Clubsport: New split-rims!

Oh yes... it's time the 330CS had some money lavished on it and what better way to start than new wheels. They are the same set of Italian-made Cromodora 18x8 and 18x8.5 2-piece split-rims that come with the car. He still has the old ones, but after 2 failed attempts to refurbish them he's been keeping an eye out for a replacement set, which aren't common. Finally some have shown up and been quickly snaffled for £ delivered. They've been sandblasted back to bare metal, then lacquered and the colour / finish is very nice indeed. Awesome.

Also, a rubber rocker-cover gasket to signify the start of the engine tweaks. Lots more to come...

E46 Clubsport: Nay's new wing! Paint, polishing... fail.

It's good to get the purple 330ci Clubsport on the pages of BeemerLab and a bit of bodywork, no less. The driver's side wing was a bit bubbly when he got the car and has worsened somewhat over winter - front wings are the classic rusting spot on E36 / E46 after all and no matter how well you patch it up, it always comes back before long, so Nathan went the whole hog and bought a new patterned wing for just under £100. Despite offers to have it sprayed professionally for next to nothing, he opted to do the work himself with a rattle can of Holt's Colour-Match, mixed at Halfords.

He started with U-Pol Hi-build filler primer to deal with imperfections in the etch-primer, moved on to a single can of Holt's 'BMW 576 Velvet Blue Metallic' and finished off with 2.5 cans of Halford's own clear-lacquer. A spray guy at work gave us a tip - apply the first coat of lacquer and wait a couple of minutes for it to go tacky but not start to dry, then apply a good thick second coat. This enables you to get a proper coat on that can then be layered on without causing crazing in the base lacquer. Nay tried this out and, after 4 more coats, some flatting back with 1800 Wet/Dry and a bit of machine-polishing, the finish is glass-like and the colour-depth superb. What a shame that, after a week spent carefully spraying one wing, the colour-match is terrible. I guess this is a lesson not to have complex paint codes mixed up at Halfords. A local painting firm is on the case, watch this space...

Only 330 M Clubsport models were built in the original three colours. Only about 40 were made in Velvet Blue. This is one of the 40 and it has seen better days. 

E21 316: MOT + New Brake Hoses.

Took the car in for MOT last week expecting to come home with a great long list of costly repairs, like split bushes or the back being too low and fouling the tyres, so I was hugely relieved to find out it had failed only on a wiper-blade and one brake hose was swelling under pressure!

To celebrate the victory I treated the car to a full set of Goodridge stainless-steel brake-hoses, front and rear, as I figured if one is beginning to swell then they could all do with replacing. The set cost me £93 from CAM Motorsport on eBay, which was slightly dearer than average, but they were the only stockist who could guarantee them in time for my re-test. For the price you also get two 1L cans of Super Blue Racing Brake-Fluid, worth about £30, which has a higher boiling-point than normal, though I doubt I'll ever get to try that out, but hey at least I had some fluid.

Oh, and I also bought the best dang Bosch wiper-blades I could find!