Hi all, l have looked over as many posts as l can, searched the net and l cannot find a similar issue with a resolution. Noticed a couple of times that the temp gauge was over halfway, but when glanced back it was back at 12 o'clock. Just dismissed it as seeing things. Now the weather has warmed up decided to get the aircon re-gassed. The aircon previously completely dead burst into life and is great. But as l have been driving around l have noticed the temp gauge going up, just before the red then dropping down to normal
At first l thought they had damaged something but after a bit of thinking l know its just a coincidence. With the added heat of the aircon and the compressor now working away whatever issue was underlying has now been made worse. Ok so plugged the iid tool in and and the engine temp goes up to 120 degrees, the rad temp drops amd is around 58 degrees, then all of a sudden the engine temp drops and settles at 105 and the rad temp increases. Then it does the whole scenario again. I have videoed this but have no idea how to add it.
Does not lose any coolant.
Can hear the viscous fan kicking in
No engine misfire
No fault codes
So as the rad is cooler than the engine amd judging by the way the temp is fluctuating l have concluded the stat is toast. Has amyone else had similar issues. Any advice would be appreciated.

Yep, defective stat or blocked rad, or a bit of both... I imagine the mechanical side isn't working but the electric side is so it only opens when it gets very hot...

If you want to do it a favour then fit one of these kits with an 80deg stat... runs lovely and cool and is much better for everything...

For now you could just remove the stat, I ran without one for months with no issue

http://www.ebay.co.uk/itm/80-C-Thermostat-...xyUrZSwcNg Pete

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Viscous fan clutch may be weak. Mine went round but not enough to cool the engine at certain speeds. The aircon fan kicks in to help, so you get fluctuation. Do the "newspaper test".

Thanks, this was my deduction also. The wax side of it not as good as it should be and when getting to meltdown point the leccy side kicking in. I feel having a car running at 105 leaves very little room for error. Towing my 22 ft caravan in july so need it right.
Thanks for the link and great minds must think alike, l trawled pages and pages of forums and the 80 stat upgrade was something l wanted to do. This mod was originally spotted on a bimmerforum and so yesterday l ordered the stat direct from abbes and is on its way. I know some people are against this but the 4.4 based 5.0 M5 bmw does not run at this volcanic temp and as l am on lpg my emissions are practically 0 and the loss of 100 yds to the gallon isnt gonna worry me. At the end of the day it is a bolt on mod using the old stat so can be reversed if needed. Is this a mod ypu jave carried out yourself? If it is l can only presume and hope the results are positive. Can you let me know how it performs of you have?
Thanks

The viscous was and still is a possibility but the radiator is cold up until the stat opens, its just toooooo hot l think l have uploaded the video right (asked my 9 yr old ) here is the link.

https://www.google.co.uk/url?sa=t&sour...dR9CHhTOvg

Hope it works might have to copy and paste.

The fan is activated by the temp at the centre of the rad, except for the first 30 or so seconds after starting. So if you stat is closed, the rad won't heat and the fan won't run. But that wouldn't explain the fluctuation you're seeing.

Thanks, yes the viscous kicks in lovely at start up and as soon as the stat opens the car cools instantly, at any speed it just does not move on the gauge but as soon as stationery ticking over it has this issue. If it was the water pump not circulating quick enough the stat should still open at the given temp. It is getting progressively worse and quicker so l think the stat is failing, the stat is supposed to fail in the open position but with a big spring pushing it shut...... Gonna try the stat first and should be able to see the water pump impeller once the housing is off. As its not pressurising and losing coolant l am keeping my fingers crossed its something other than engine related. Stat, water pump, rad temp sensor for the gauge or gauge issue. Not ruled anything out yet and will keep updating as and when l find more info.

Bare in mind the viscous fan can look like it's turning and doing something but it may not be engaged hard enough due to the viscous fluid disappearing over the years. Hence why mr_spock mentioned the newspaper test, if you can stop the fan with a rolled up newspaper when it's supposed to be engaged fully (i.e. hot) then the viscous coupling is not doing it's job. Obviously it's a test that needs doing carefully using some common sense.
I've had it happen to me before on another viscous fan on a BMW which caused overheating when stationary, it looked like the fan was working but simply was free wheeling and not pulling enough air through (air con fan was toast so that didn't kick in).
It worked fine when moving as natural air flow was enough to keep it cool. Newspaper test confirmed the viscous coupling was knackered. I ended up replacing the viscous fan with a decent electric fan.

Yep defo not ruling it out in any way and using a newspaper is a damn good idea, l used to use a leather glove to do the same but as in a wheelchair now a bit tooooo risky. The video though shows the rad temp as being cool compared to the engine and as mr spock states the fan gets it heat from the radiator if the rad is not getting hot the fan will never kick in properly. To me it feels like it could be any of the issues oulined. Why do l always get the unique issues..... Gonna start it up in a mo and see if l can talk the mrs into putting a newspaper in whilst it is kicked in. Its somerhing l can test without cost and risk. Wish me luck......

If that were me I would look into a full cooling system overhaul. Piece of mind end of the day. Just a thought.

Trust me if finances were better l would do the lot, but as it is l just cant afford to. It is all in my plans as she has done 99000 and has no service history, was gonna change rad and stat anyway but up till now had not been an issue, replaced rear brakes and handbrake shoes a fortnight ago, serviced the engine a month ago and changed all front brakes 2 months ago, got silicon upgraded breather pipes and new rocker cover gaskets so they will be done soon too. There is never a good time to get issues, but there couldnt be a worse time. At the end of the day the car is 13 yrs old so not upset, just bad timing. But defo a complete cooling system overhaul would be the way to go and eventually will be done.

I had a combination of issues which caused symptoms like yours:

1. Weak fan clutch
2. Low coolant level, made worse by:
3. Coolant level sensor lying!

I suspect the rad wasn't great either as it had clearly leaked. I therefore:

a. Changed fan clutch
b. Bled system and filled with distilled water to test (was OK then)
c. New rad and expansion tank
d. Refilled with correct coolant and bled

It's fine now.

Yep got 10 itres of a/f andriend who is looking to break an
10 litres of distilled water yesterday, once the stat comes will drain system, flush change stat and re-fill. Thos si why l am so confused when the fan went on my carlton gsi it was fine driving but when ticking over would get hotter and hotter and hotter. The rr is similar but cools down gets hot and cools down, doesnt overheat and has not used a drop of coolant in 4000 miles. A friend is looking to break his 07 diesel so gonna do some digging and see if any parts are interchangeable, fan and rad may be the same....

I had the same symptoms. Exactly.

Engine starts cold, good
Engine heats, weak fan means it doesn't heat up mega fast but it still gets hot. Depends on how weak it is too. (gauge goes up to centre)
Engine heats more, fan can't cope (gauge up)
Drive over 40, airflow cools the rad enough (Back down)
Also, aircon fans kick in enough to cool the car under 40 ish on a day if it's not too warm outside. (gauge goes back down)

That's your fluctuation.

If the thermostat was stuck shut, the temp should just go up. And up. Eventually you'll lose coolant as the overheat=overpressure and the expansion tank cap releases coolant and air gets in.

Oh, by the way, if you look in the expansion tank and see coolant, and the indicator shows it's full, DO NOT TRUST IT. I got 3.5 litres of coolant into mine under those conditions! New expansion tank was the solution to the indicator, although just filling it up and bleeding solved the heat issue (with the fan replacement).

I have not tried putting any coolant in, just trusted it...... Gonna go mix some and attempt a top up, the fan seemed solid on start up a few minutes ago. There is a float that bobs up in my expansion tank that shows coolant level. Should this not be there l wonder.