This was my Smiths sender in a collar to fit the BMW head compared to the original - you can see why I was not happy with it!


https://farm8.staticflickr.com/7100/...96a215eb_n.jpg

Even after I trimmed the collar back as far as I dare there was still not enough reach into the main waterway

https://farm8.staticflickr.com/7213/...d863e8cd_n.jpg

Water Temp Sensor/Gauge Saga
 

Despite ordering a special Smiths classic VDO temperature gauge from Caerbont designed to work with my BMW VDO sensor, when I tested it to calibrate the scale, I could not get a reading.

I then bought a new sensor, thinking it must the problem, but it did not work either.

After a chat with Caerbont technical services and testing the resistance profiles, they advised they would not work with the gauge they had specified, and would I send it back with my sensors, and they would see what they could do?!

This has now been dragging on for weeks..............and I'm still waiting!!!!!!!!!

BMW M50TU Vanos
 

BMW M50 VANOS - Variable Valve Timing

The internet is a wonderful resource for finding information easily..............and finding problems too, real or imagined!

The following may not be of general interest, but hopefully may help anyone using a BMW M50TU engine in their Marlin in the future.

Driving back from Stoneleigh was my first long distance run, and allowed me to get a feel of my Cabrio's performance. Subsequent driving has confirmed my initial assessment that it pulls very strongly over 3000rpm, but I feel is disappointing below this band.

Trawling through the BMW forums was both reassuring and worrying.
The M50, with its steel block straight 6 cylinder design has been refined through almost 2 decades such that it is incredibly robust, often exceding 200k miles. However, with the M50 TU (stands for Technical Upgrade) BMW introduced their first variable valve timing system - VANOS. This is designed to improve the power delivery over a wider rev range, and improve fuel efficiency.

http://www.marlinownersclub.com/foru...2&d=1402088026

The Vanos unit bolts to the front of the head and is the bulge on the right side when viewing the engine as above.

VANOS works by applying controlled oil pressure on a piston which acts on a helical gear set to vary the angle of the Inlet camshaft relative to the Outlet cam/crank.
When new it works well and performs as designed.

However, having trawled the BMW forums, looking for why my engine was less strong below 3000rpm, it became clear very quickly that there is a design weakness in BMW's VANOS: the oil pressure seal is made of inappropriate material, and is usually worn out by around 70k miles. This allows the helical gears to oscillate in and out against the Vanos piston producing the commonly known "VANOS rattle".

There are a couple of remedial actions which can be undertaken with the M50TU Vanos.

The first is to buy a new BMW vanos unit - very expensive!
Secondly buy a refurbished unit from an after market supplier called "DrVanos" at a more reasonable cost (Very good apparently, but still £250).
Thirdly there is a DIY option: Beisan offer a seal kit which cures 95% of the problem for a much more reasonable total cost of around £30. Better still, the new seals are made of material more suited to operating in oil and heat, so are longer lived than the genuine BMW VANOS units.

There are several very good Youtube videos on how to change the Vanos unit, and seals, and it looks pretty straight forward, so this is the route I'll take. The kit from Beisan comprises just two seals, and a new bearing housing:

https://farm4.staticflickr.com/3842/...8a3c586126.jpg

(- the videos below are 25minutes long, but if you want to know what to do are very good)

Vanos Removal
https://www.youtube.com/watch?v=JPlKrOC718w

Vanos Install
https://www.youtube.com/watch?v=23jXHhkpV_I

BMW were quickly aware of the "Vanos Rattle" and introduced an upgrade in the M52 single vanos engines, changing the single plate No. 9 in the M50 to 3 plates Nos.9, 10. & 11 in the M52.



M50TU Vanos

http://www.realoem.com/bmw/diagrams/d/k/2.png

M52 Vanos

http://www.bmwmobiletradition-online...rams/d/a/9.png


As with a lot of BMW developments this upgrade can be retro fitted to the M50 provided the longer studs (#6) are used too.

The improvement comes from the "Cup Washer" #10 which is a compressed dish plate between two flat plates #9 (2mm thick) and #11 (4mm thick), and helps to stop the cam advance oscillating. It has continued to be fitted to all later BMW heads, so presumably does work.

Ironically BMW charge only £3/4 for the cup washer plate, but want over £30 each for the two flat plates (#9 & #11) - so I sourced a pair from a BMW breaker for £10 delivered!

https://farm3.staticflickr.com/2908/...11e1acd7fe.jpg

Of course things are never quite as easy, or as cheap, as you first think, and I've ended up buying a raft of genuine BMW gaskets to replace the old ones when I make the upgrade as the plastic gaskets become brittle and fail on removal:

https://farm3.staticflickr.com/2923/...18806a7a2b.jpg

My expectation is that these upgrades will help improve the low down torque, and eliminate an odd "rattle" I can hear in my engine around 2700rpm - by all accounts a classic Vanos seal failure symptom.

VDO Temperature Gauge
 

After a further 4 weeks Caerbont have now told me their VDO 'Low' Temperature gauge will not work with the BMW sender!

However, they have a programmable gauge which will work with the BMW VDO sender (as it can be programmed to give the correct reading for a given temperature) - but of course it is more expensive!

Rock and hard place come to mind.........

Extensive VANOS post, I'm sure it will be really useful for anyone with an M50. Look forward to hearing how it goes :)

I haven't done the VANOS seals on my M50 but I did do them on my 130K M54B25 as I also perceived a lack of torque low down. The old seals were very brittle and flattened but the new ones didn't make a blind bit of difference as far as can tell, either on performance or economy. I've come to the conclusion that the BMW straight six is just not a very torquey engine low down. My old 3.0 V6 used to pull hard from 1500rpm but the straights seem to be a different kettle of fish.

I hope if makes a difference for you though. Have you got the special tool for setting the cam position or are you going to fabricate something?

Your m54 should have plenty of bottom end torque - have you checked your DISA valve - these are very prone to wearing out?

You may be right about not improving the M50 bottom end torque...... it will be interesting to see? If it solves the strange "rattle/rumble" noise I get at 2700rpm I'll be pleased enough.
If the torque improves then it will be a welcome bonus.

The M50 is known to have relatively aggressive cams, which have been tamed with each new M5x engine. The M50TU is milder than the M50, and the M52 milder than the M50TU. The forums suggest the M50 has been criticised for lack of low down torque, and the M52B28 was introduced to produce its torque lower down the range (due to milder cams).
The M54 introduced DISA which allowed a more aggressive cam to be brought back for the top end, but improved the bottom end torque by changing the inlet runner lengths between slow and fast revs.

I've not looked at the M54B25, but the torque figures for the M54B30 make me very envious! So much more torque, and significantly lower down the rev range too - my kind of touring car engine!

A spot on one of the forums showed a very simple way to set the cams - place a flat bar across the tops of the flat cam lobes, and then clamp them with two G-clamps - very simple and works a treat.
I'll make myself a bar with two pins to rotate the exhaust cam sprocket to push the Vanos unit off. It seems fairly easy for a single Vanos unit.

yeah it was the tool to rotate the cam sprocket I was thinking of. They don't cost very much but the proper tool for clamping the cams themselves costs well over a hundred.

My 325 is an auto too which also kills some of the low end and torque across the range generally. Once I've recovered from the £470 worth of parts I've thrown at it in May :( I was planning on doing a transmission fluid drop and refill, new filter etc in the next month or so. That should help a bit.

My DISA is fine, it was one of the first things I check when I bought the car to make sure that the pin wasn't about to drop out and take out a valve. You hear a definite change in engine note at around 4K rpm that I've always assumed was the DISA cutting in but may be wrong, that may actually be the VANOS cutting in?

Mike

Where did you get to with your temp sensor problem?

I have used the Smiths eclipse gauges which also do not work with the standard BMW sender.

The m20 also has a long sender tube which gives me the same issue you have.

The 1/8 NPT sensor with adapter supplied by speedycables provides about 20 mm less length into the thermostat housing than the original even cutting the adapter down as much as possible.

I assumed when they said they did a solution for the m20 it would be the same length (a fool and his money). It means the sensor is buried in a threaded tube in the thermostat housing with only 5 mm of the sensor exposed beyond the thread adapter, speedycables say it will be fine but I remain unconvinced.

Just wondered if you had found a solution.

GOO / Patrick did you have similar issues and how did you sort it.

Any info most appreciated.

John

On further examination there are two spare take off ports in the thermostat housing which are blanked off with 14 mm studs. One of them has a much thinner threaded boss which will allow the new sender in its adapter to sit in the water flow.

Both spare ports are on the hot side of the thermostat so I think should be fine, does anyone happen to have a spare 4 port thermostat housing lying around that they could sanity check for me to make sure the spare ports are open to the original sensor location just to save me taking mine off the engine to check. I can't see any issue with using the front spare port.

Cheers



John

Hi,

I used the supplied senders that came with my instruments - and I got all of them from ETB

http://www.etbinstruments.com

Never had an issue with them - so can't really comment further. Sorry.

Hi Jason

Without knowing I think you have answered the question.

I looked at the ETB sensors on the link you provided and the sensor they supply for their gauges looks to be the same dimension from the pictures as the one I have for mine.

I can see from your pictures on your website of your installed sensor that its fitted into an adapter boss exactly as mine would be, and is "buried" in the thread of the adapter and thermostat housing thread in the same way.

I think the fact you have seen no issues with this setup reassures me that speedycables are right and it should work fine. I am maybe trying to fix a problem that doesn't exist.

I'll fit it as is and see what happens when I fire the engine up for the first time.

John

Hi John

Looking at my new, as yet to be fitted, housing and checking with the actual M20 installation on my spare donor, the 2 fitted senders (brown upper blue lower) are on the top hose side of the thermostat. The 2 large blanking plugs are on the bottom hose side of the thermostat. As you say, one of these has a much better penetration into the water flow than the other but whether they can be used successfully is another matter. Incidentally the original senders penetrate approx 5mm into the water flow.

Sorton

Hi Sorton

Thats what it looks like on my fitted unit but the two sides are open to each other as shining a light down the brown sensor hole you can see light from the spare blanked ports and all four ports are on the hot side of the thermostat. That said it looks like the shared sides are partially restricted as the hole behind the thermostat looks to be about 30mm ish.

The Bentley manual shows the flow as you would expect, I assume the partial restriction in the housing is sized to balance the flow of water once the thermostat opens.

I think as Jason has seen no problems fitting his etb sensor with adapter in the correct port I will try mine in the same and set up a reference temp sensor to check the reading on the gauge. As you say the original bmw sensor length allows about 5 mm into the housing, with the short sensor and adapter I have I figure its about 10 mm inside the threaded part of the housing which doesn't really feel right but I'll give it a try and monitor the engine temps with a contact temp sensor.

John

I also have etb instruments. I have never had any reason to doubt the temperature gauge. It is always rock steady and bang in the middle under normal conditions.

Cheers, Robin

I got my gauge and matching sender from Marlin - I use a thread adapter to fit it into the stock brown sensor location and it's been fine:

http://www.msportster.co.uk/gallery/...ts/parts26.jpg

The M14 x 1.5 on the right is for the temp sensor. I've not had any problems - it sits at 80C until you sit idle for a while, at around 85C the fan kicks in and keeps it there.

I had more problems with the original radiator/fan combo getting too hot. I'm using a big ali radiator and 16" fan now. There some pics of the rad install here: http://www.msportster.co.uk/2008/06/...diator-fitting

http://www.msportster.co.uk/2008/06/08/cool-runnings

The photos show the original 12" fan which I've since replaced with a 16" fan. Sufficed to say I don't have heat problems any more.

Decision made then, cheers Patrick

John

Hi John

Sorry for the delayed response - been away on holiday.

Although you seem to have settled on an answer to your own question, one comment I would add is that when talking to Caerbont/Speedycables they said their sender/gauge only operates as a zone guide and should not be regarded as an incremental scale, and offers no idea of what the actual temperature is!

They then volunteered that they have a programmable electronic gauge which could be calibrated to my own original BMW VDO sender to give a true temperature read out. As this allowed me to keep my BMW sender (and will be really important when I swap to the M54 alloy block which is known to be sensitive to damage through over heating) I went down this route and chose a face to match my other Classic Smiths gauges.

Hi Mike

Hope you had a good holiday.

Reassuring words then on the speedy cables front!!

I've fitted it all now but do intend to carefully monitor the temp on first startup with an independent and more importantly ukas calibrated temp gauge that I managed to blag from work on loan.

John

Its not just Speedycables - a BMW elec tec told me the BM gauges are designed to sit rock steady at "Normal" over quite a wide temperature range - but if they do move off normal towards "high" it is likely you will have done damage to the engine already.