That's why I haven't heard any fan switching on/off then --
haven't had the aircon on since collecting the car back.

Just been out again and the temp needle didn't even flicker from its half position -- didn't push it though, Saturday afternoon shopping traffic in and around southeast London. Tried with heater on full too (negligable heat output)

What I did notice just now though was a slight moisture weep from around the new coolant resovoir's cap. Didn't realise that much torque has to be applied to ensure a seal there. Had a look as fluid escapes from resovoir's undone bleed screw -- there were a few, just a very few, very very tiny bubbles coming up in that. My mechanic has offered to check with his kit to see whether they are combustion gasses or not. There's no mayonnaise on dip stick or filler cap. Guess this coolant's too new (just over 100 miles) to tell yet?

But today's last trip back from Crayford to home (12 miles) did give me the temp gauge once slowly creaping up to beyond the ¾ mark before falling back fast to ½ again, then staying there

I would say it is an airlock...the M62 is notoriously difficult to bleed properly.

Vid here from a uber BMW man, much respected in Bimmer circles....



I had curious temp gauge readings, and it turned out to be a chaffed wire from the sensor grounding out and causing the needle to fluctuate....so check that out too....but 1st thing, make sure the cooling system is bled through and rid of airlocks...

I'll follow that vid to the letter -- thanks for bothering to post it, much appreciated. Just went out and heavans opened.
Can't assume previous mech followed that procedure what with being a Merc head. But after getting back from Bromley and having the "up to ¾ FSD" experience just the once then, did check the expansion tank level when engine was cooler. It was float level OK. So had then probably introduced air into the system again then. And have been chasing my tail in ignorance ever since. Once rain's stopped will follow vid procedure.

Previous keeper lists having changed expansion tank. Merc mech reports having found an 84º electrical thermostat in on a bridge. This has been changed back for a new 105º
All at the time of not knowing that the heater hose coupling at the rear of bell housing was then leeching before it finally went big time. Merc mech reports as exactly like in the vid I posted earlier. (It'd be useful if Jubilee clips with rolled edges were used as OEM sometimes...)

Tim's vid shows a pic of a piece of rag wedged down the expansion tank filler cap's hole. Why? He doesn't make reference to it...

Save anyone else without the latest n'greatest iPhone from writing the procedure out from the vid:
Use this procedure from cold start only
You only have five mins to complete this
Park facing up a hill
Catch bowl (old washing up bowl or similar) under engine to catch spilt coolant
Take off expansion cap
Take off bleed screw
Heater on full in all directions
Start engine to idle
Top up coolant level to float high (top just above top of filler neck as embossed diagram on tank shows)
Rev up engine to see coolant coming out of bleed hole
Keep level in expansion tank correct after revving, i e at idle
Refit expansion tank cap fully (I'd not known this means tight, not just like old-style radiator caps)
Rev up engine again with bleed screw still fully removed
See some slight coolant coming out of bleed screw hole
Refit bleed screw for 30 secs
Remove bleed screw
Rev up engine again with bleed screw still fully removed
See some slight coolant coming out of bleed screw hole again
Refit bleed screw fully
You (should be) done

Think I've got this right...

Just completed above procedure, didn't see any of the tiny gas bubbles in the overflow from the expansion tank's bleed hole. Got to complete procedure just as temp gauge was nearly at ¼, slight warmth coming from heater vents.
LPG had not yet switched on

Followed this recommended procedure (the above video) from:


Took out from Blackheath to Plumstead light foot all way crawl heavy traffic and
behaviour was solid staying at ½ FSD. Coming back gave it some wellie on a quiet
stretch of road and up hill -- after which needle went just over ¾ once but seemed to stay
there longer than usual before falling back again to ½. Fuelled up ready for tomorrow at
Charlton one swing up to ¾ then back again to ½ on the way home again after
climbing hill and so increase in revs to 2,500.

Motor factors shop didn't have the chemical for checking for combustion gasses in coolant
Mind you, they didn't even have the check tabs that show if brake fluid has too much water
in it. What's happening nowadays?

Baffled -- will find out how constant 60mph up to MK (via Blackwall, M11, M25, M1)
and back affects on motorway tomorrow. What could possibly go wrong?

Still sounds exactly like my old cavalier was when the water pump impeller was loose on the shaft. Exactly the same symptoms.
I'd be checking that again.

Yes, I haven't changed the water pump. But previous keeper did list it in his list of things he'd done (now three years ago but that was in his sales blurb ) Merc mech says water pump's OK though. Apparently these sort can be checked if there's play felt by woggling the shaft from side to side

Years ago was a Dub head and VAG went through a spate of bad plastic impeller water pumps -- cheeepo Chinese made -- so they had to start a spares' sales procedure that they would only give a return credit on an old water pump bought from them when old one returned so that they could check it was a genuine VAG one, so good a copy was the counterfeit from the likes of Euro-cr... and other factors

Bring up the hidden menu on the instrument display and call up the coolant (KTMP) digital reading....

this will give a digital readout of the temp display which you can monitor and check against the gauge reading....see if it climbs steadily or if it is a sudden jump.

Climbing steadily would show there is a cooling issue (airlock, blockage, dodgy pump, leak, etc) or a sudden jump would show an electrical issue.

Will try that. But if that's shown on the LCD display fear might not see much as a few pixels are not working so only about ⅔ of that display is actually de-cypherable

<later> well have gone thru what's available both on the HUD and the LCD and can't find any display that's giving a running temperature. Still, as its "hidden" then that's probably not surprising.
Go on, tell me how to access? You know you want to

Decided discretion was a good idea so cancelled my appointments in MK -- no sense in risking a warped head --
I've already got one of those

RichardSEL said:

Will try that. But if that's shown on the LCD display fear might not see much as a few pixels are not working so only about ⅔ of that display is actually de-cypherable

<later> well have gone thru what's available both on the HUD and the LCD and can't find any display that's giving a running temperature. Still, as its "hidden" then that's probably not surprising.
Go on, tell me how to access? You know you want to

Click to expand...

Ignition key must be “off”.

• Press and hold the Check Control button in the instrument cluster (RIGHT button), and turn the ignition key to the first position (KLR).

• You will first see "Check Control OK", some seconds later you will see "Test Nr.01"
• Push the left button on the instrument cluster to see the car's identification number. Add the 5 digits (not 6) together and write down that number, you will need it for unlocking all the functions. Example: A123457 will lead to 2+3+4+5+7 = 21
• Push the right button until you see "Test Nr.19"
• Push left button until you see the number that is equal to the one you calculated above
• Push right button again

1. Display Car's identification number, HW/SW version, construction date
2. instrument cluster self test. Will light up all lights and run all guages
3. Current consumption (liters/hour)
4. Average consumption (liters/100 km)
5. Current range
6. Remaining fuel in tank. Three sets of numbers: A/B/C. C=total amount.
7. Engine RPM / Coolant Temp (C)
8. Current Speed (kph)
9. System voltage at Term. "R" (Battery Voltage)
10. Country/Language (UK, US, Spa, Ger, Jap, etc.)
11. Units am/pm
12. Average Speed
13. ETA
14. Date of Software Mask
15. Production Diagnosis
16. ""
17. Display Vehicle Specific Data
18. Alarm Changeover (cont. vs. intermittent OBC chime)
19. Lock/Unlock
20. Correction factor for fuel consumption (nicht ändern!)
21. Reset all defect codes


(Copy Pasted from fullfatrr.com)

Ah, right. I should've known that. Silly me

... every day I'm getting better, and better, and BETTER
(film, yes but from which film?)

Because of your and this forum's support I will not be beaten -- well, not by an L322 anyway

Driving around lightfoot trying to find a shop with the gas-in-coolant detector kit (Halfords Crayford, plus Dartford, and Plumstead olde style parts shops = nothing) this symptom only ever occurs when I have to accelerate causing the temp needle to go over the ¾ mark, stay there temporarily, then fall back.

As you'd mentioned that the current coolant temperature was available for display figured it must be available from CANbus data so my iCarsoft i930 should see it too. Wondered whether there was a delay between this new
(eBay found stipulated for the BMW M62) electric thermostat reacting to temperature increases caused by greater loading on the engine. Trying to drive at the same time as performing down shifts performing greater load while viewing temp gauge and the iCarsoft all at the same time was interesting. What I can confirm is that the iCarsoft is reporting electric thermostat being "On" and "Off" during the temp gauge going up and down. But whether there's a delay (think there must be) I've not confirmed.



But there's more. Given that before all these dramatic dumping of coolants over various motorways in the southeast I was driving on LPG, and given that there was some problems with switching over from petrol to LPG on warm up (had to press the button multiple times to get the system to changeover but that fault's not happening now) decided to drive back from Dartford via A2/A102 with LPG switched off. Got back and even when I got to Blackheath Hill where the car usually drops a gear and afterward temp gauge swings upward there was no swing upward this time.
Course I'm keen to clutch straws to assume there's something amiss with the LPG system -- avoiding believing there's a head gasket leak -- both mechs that have had this have wondered the same LPG thing. But apart from reading that changeover's temperature controlled and the system's LEDs are pressure controlled, I know not much more.

Now I've got that hidden menu will try exploring it tomorrow together with my iSoft to see whether the Coolant Temperature readout on it is dynamic if my LCD display's not up to showing that menu to give any real meaning.

Lpg normally has its own sensor on the vaporiser.
Does yours have the electronically controlled viscous fan or is that only on the jag engines?

Wazzajnr said:

Lpg normally has its own sensor on the vaporiser.
Does yours have the electronically controlled viscous fan or is that only on the jag engines?

Click to expand...

Thats the Jaaaaag engined version - the M62 uses the traditional bi-metallic spring method!

Saint.V8 said:

Thats the Jaaaaag engined version - the M62 uses the traditional bi-metallic spring method!

Click to expand...

Thanks again for your experience & insights. Most useful

The engine fan on my M62 is just the viscous-coupled one. I've already had the viscous coupling changed for the BMW M62 equivalent one. Today will see some definitive driving tests to confirm whether this fault is showing only on LPG or both fuels. Just out now to see whether the LCD display is sufficiently readable to get into that "hidden" menu

Just been out to attempt (with an LCD display that has missing pixels) access and read the "hidden" menu.
I can de-cypher "Check Control OK", and "Test N?01" I then push the left button and get "FGSTN?¦: A13042׀
I've read that to mean totalling 10 as I don't know what the last calligraph character is in missing pixels.
Pressing again the right button to try and match the total of the last five numbers, or 9+׀
brings me to starting the Instrument Cluster Self Test (all OK) -- #2 on the list.
Pressing further the left button until I believe I've reached #7 on the list just brings up "LOK #/??"
So it seems I've insufficient pixels to read to actually key in the correct codes or to access the system.

But I still have my iCarsoft that I believe its Coolant Temperature readout is dynamic so will try that later when the rush hour traffic's lessened.

... hi-ascii characters entered into this message may not display correctly as keyed. ? means unreadable

Saint would know but I seem to remember a mod where a lower temp stat was put on some engines. Cannot remember why though.

Yes, a previous owner was either an enthusiast or had problems like what I'm trying to fix.
A previous mech said that he'd recommend next change the electric thermostat as an attempt to cure.
When I'd already asked them to change that plus the ECT sensor plus the resovoir cap. And
they just changed the viscous coupling and flushed out and re-pressed up with coolant. That
lasted the return trip plus another couple of weeks before loss of coolant was happening again.
Apparently the hose -- union to the heater feed at rear of the bell housing leeches first at the
Jubilee clip before deciding to let rip big time...

When current mechanic actually did the repairs that I'd originally asked the previous mech for he found that the electric thermostat fitted was on a bridge and it was an 84º one not the OEM 105º that he eventually fitted as a replacement. He said the 84º one that he took out was OK though, just that it'd been fitted wrongly trapping the "O" ring across it's fitting recess and not entirely in it I too don't know why that was a much favoured mod back in the day. Does it need re-adaption or re-setting in the ECU program?

I'm now running on petrol only and seems the temperature's rock solid showing half temperature meter at the moment. Can't avoid a trip going 30 miles or so today.
But switching over to LPG seems to produce these odd temperature needle swing ups and then
back down to normal again. Have ordered the cheap eBay CO2 sniffer tester so will know today whether
there's combustion gasses in the coolant. Or whether there's LPG leeching past the Vaporiser/Reducer
and into the coolant that way and causing the fault when on LPG -- hopefully the sniffer's fluid doesn't also react to LPG

Vaporiser -- Reducer: two names for the same component?
Is it the part with the Prins label on it in my pix?

Yep that's the vap.

Your sniff test shouldn't detect LPG as it is testing for burnt hydrocarbons in the coolant space.

It is very strange you only get temp fluctuations on LPG only - unless the Vap seals are leaking past and causing an intermittent airlock in the cooling system.

The stat mod is because the M62 engine runs at 105degC which is super hot - it helps for a more economic mpg, but leaves very little headroom for any over temp - CH damage can occur over 120degC...so only give 15degC of wiggle room - that and the gearbox is 'cooled' by the coolant, and anything over 110-120degC can frag the gearbox fluid. Also, high temps can cause plastic fittings to go brittle and crack!! So the M60 running temp stat at 84-85degC can be modded to fit, allowing the engine to run cooler, cooling the gearbox fluid better, more overhead for pushign the engine harder when off road or towing, saves the plastic fittings etc.....MPG determent is minimal in reality.

The electric heated stat, keeps the engine at 105(ish) for the majority of the time, but when you put your boot down, the engine ECM heats up a coil inside to open the stat further to provide more cooling and can get down to mid-high 80's when tanking along....only for it to close again when less spirited or 'hardwork' driving has ceased.

If the stat heating coil is fecked, and you are demanding more from the engine, the temps can creep up as it is expecting the stat to open further to increase cooling...but this isn't happening hence temps climb.

The temp gauge centre point is anywhere from 70-110degC I believe so there is a ~40degC 'tolerance' when it sits vertical, it starts to move to the red above 110 and I think red zone is 124degC....so from 105degC baseline to needle movement toward the red is only a matter of 5-10degC or so....which is not a lot of increase compared with 105degC running temps - hence the 84degC stat mod - it just gives more latitude without affecting engine performance. although it should be said, a well maintained M62 should run perfectly well with the OEM 105degC stat....and fitting the mod should only be done because you have a specific need to do so - towing a 3.5 tonne trailer in Dubai in the Summer! - although the peace of mind with having that extra headroom temp wise is tempting!