CDTi Thermostats - Why they fail, how to diagnose yours and how to fix.
 

If you have a 75 or ZT CDTi, you may have noticed your temperature gauge never reaches the middle of the dial.

It should do this during normal driving - 3-5 miles of normal driving should see you have a healthy 9 o'clock reading on your gauge. If not, read on!

Why do they fail?
It seems the BMW thermostat fitted to the M47R suffers with sticking open - it's reported widely on BMW owner's clubs, on Land Rover forums (the Freelander TD4 shares this engine) and of course on this forum in the many threads discussing the issue.

When your thermostat is stuck open, the engine will be over-cooled and you'll suffer with low running temperature - reducing fuel economy. Normal operating temperature for the M47R (when driving) is usually around 85-90 degrees Celcius, with this increasing when sat in traffic or idling with no movement. The fan will cut in to prevent overheating if this is the case, however when on the move the CDTi won't make enough heat to make this a necessity.

9 o'clock on the temperature gauge is 75 to 115 degrees C - the chances are if you reach 9 o'clock and this doesn't change when driving your thermostat is OK. You can test the exact running temperature by going into the integrated diagnostic mode built into the Instrument Pack - T-Cut has made an excellent guide on this subject: https://www.the75andztclub.co.uk/for...38&postcount=1

How do I fix this?
Luckily, fixing this issue isn't as hard or complicated as it used to be.
If you're after restoring normal functionality with the minimum of fuss, you can fit the thermostat from a Renault 5 into the top radiator hose (at the engine end). This is a simple affair, as detailed below:
- Cut through steel band securing top radiator hose to engine coolant outlet
- Fit thermostat into top hose, with the copper bulb facing the engine (You'll need to grind the collar of a standard Renault thermostat down a little, however the kits I supply are already ground ready to fit)
- Secure the thermostat with a Jubilee clip, and use another Jubilee clip to re-attach the pipe to the coolant outlet
- Fill the header tank back to the 'maximum' position, and run the engine for a couple of minutes to circulate coolant. Check coolant level and top up if needed.
- When using the car for the first time after this job, check the coolant level once a warm-up cycle is completed (make sure your coolant is cold again though, hot coolant can scald if the cap is removed when the system is under pressure).

I supply both the OEM thermostats, and the Renault 5 items.
Renault 5 Thermostat Kit, including pre-ground thermostat and 2x Jubilee clips: http://www.dmgrs.co.uk/collections/t...tat-89-degrees
OEM Thermostat (BMW): https://www.dmgrs.co.uk/products/r75...evised-version

*NEW SOLUTION AVAILABLE - V3 ORIGINAL STYLE THERMOSTAT*

We've worked with a major thermostat manufacturer in China to have a revised OEM-style thermostat made - this has been dubbed the 'V3' item (early diesels used V1, which didn't suffer with many problems - then V2 replaced it, which suffers with opening early).
This item shouldn't suffer with opening early as the V2 items do.

This item is a bargain at just £29.99 - available here: V3 Thermostat - CDTi 75/ZT/Freelander

I've also written a How To about changing the original thermostat:
https://the75andztclub.co.uk/forum/s...d.php?t=245051

Plenty on the shelves now... :D

http://i282.photobucket.com/albums/k...9.jpg~original

Can I order through you direct here, Or do I need to create an account on your site mate ?

Cheers

Pete

Well, decided to go to your shop and order one mate

Look forward to receiving it. :D

Can you confirm you received thr order?

I have indeed, thank you. :)
Shouldn't be long until you receive it.

Bookmarked for read when i get home :}

Finally fitted the Renault 5 thermostat
 

Finally, fitted the Renault 5 thermostat and went for a drive. It was a cold wet day driving in south east London, a maximum recorded temp of 93 Celsius was achieved!

Excellent! Just what we want. :D

Ordered 1 anyway as mine deffo not reading correct, sitting just about 8 o clock i reckon and not 9 as i want.

Good stuff - 9 is anywhere from 75-115 degrees, so 8 is far too cold. :)

Just ordered Matt, Ours is struggling to stay at 82-84c and drops to 70's when moving..

Thanks for your order. :)

Do you do the remote stat?

Hello there, unfortunately not - my apologies. :)

Just done the test on mine, 81-84 degrees, dropping to 78 when moving - would say stat is fubar?
My questions is ; when fitting the renault (vomit) stat, do you have to remove the old one. I will admit now that I have not read the info on fitting it, and could this lack of engine temp be the cause of having to crank my heater up full to get hot air to the screen?

Ta..:D

Yes I would say it is fubarred, especially if it takes more than 3 or 4 miles to reach at least 80 degrees. It is close to being fubarred anyway.

You wont need to remove the original, as it isnt known to fail open or closed, but rather it fails by opening too early.

Installing the Renault stat, is a relatively simple job, I have now done it a few times and can do them in about 10 minutes lol.

There are other options, but none are as easy and as cheap as the R5 stat. It will help get the temp up higher to the accepted operating temp. Before commencing any work, fill the bowl of the stat with water and make sure it is water tight. If it is not, reject it, for you will notice no difference.

Dont bother trying to crank the heat up, cold or warm, just turn the AC on it will clear just as quickly. ;) even in cold weather.

re stat
 

Nice one CLF,
regarding cranking the heat up, I am more concerned about the chill factor to my fingers tbh :D. Do you recommend changing the manifold seals / gaskets at the same time? If so, I can order the lot from Matt in one go.
Only problem I have is the three screw holding the intake to the slam panel are just spinning, guess I can just wedge the whole thing out of the way though.

cheers,:bowdown:

which manifold? the air intake manifold? if it is, you dont need to touch the manifold to remove the top hose. Two of my screws in the intake hose were spinning, however, I simply lifted the top of the slam panel as I unscrewed and they came out. You can buy new nuts on ebay cheaply, however I cannot remember their name, but I have never bothered. (incidentally, you can get away with pulling the hose away from the intake and sliding it over - but you dont even have to do that).

If you are removing the intake manifold for whatever reason, whilst you shouldnt need to replace the gaskets, it is good practice to replace.

If you are replacing the original thermostat, I havent done this yet, however, I believe you WILL need to replace the OEM thermostat seals. (the R5 mod has none to replace).

If it has never been done before, you will need to cut the steel band on the hose at the engine side, ultimately replacing with a hose clip. To cut, I used a junior hacksaw, scored the band with the saw, and the at its edge until cut through, then with pliers, peeled back like a corned beef can. Have you seen the how to for replacing both stats?

Jule's How To

Arctic's How To

Mat (DMGRS)'s OEM How To

Just remember to check for the water tightness, by filling the bowl, all the effort will be for nought if it is not tight.

Not watertight

Watertight.

Fantastic post above - thanks clf.
I don't think I can add anything else of use! :D

Replacement stat received mat
Thanks buddy- yr the man :bowdown:
Regards
Chris

No problem at all, happy to help. :)