dkeenan

Thanks very much everyone for the help. I eventually got the temperature from the hidden computer and it's maximum running temp is 61° C. I think I might chance changing out the main thermostat for an OEM part.

dkeenan

One other strange thing that happens is that I can start the car and drive it and it will not heat up to normal temperature but if I drive it for ten minutes and stop for five and start it and continue to drive, it will more than likely heat up to the correct running temp. Also flooring the accelerator after ten min of regular driving will help the temp to increase to normal also. I'm thinking perhaps the spurious thermostat is somewhat sticky perhaps.

dkeenan

Thank you everyone for your replies. It seems that I have fixed the problem. I bought a genuine BMW Thermostat and fitted it. The car now heats up to 88 degrees straight away. The spurious thermostat seems to have been faulty from day one. This is the installation guide I used:

To improve the running temperature to a nominal 92C you may need to replace the Main Thermostat. This is how I did mine:

Remove the acoustic cover (5 allen bolts) (and oil filler cap temporarily).
Remove metal panel above radiator (approx 10 torx screws) and put to one side, leaving the bonnet pull cables attached (don't short the battery charging point with the big metal panel).
Remove plastic panel under that (5 torx screws, careful not to drop them).
Reach down to bottom of fan and unclip the 1" hose that runs across the bottom of the front of the car. It just pushes into two U shape bits on the fan cowling.
Unplug the two plugs to the fan.
Wiggle the fan up and out (you have to squeeze the big EGR air intake hose at the top quite a bit, or it might be worth unclipping it).



You can now see what you're doing.

On my 535d I have an airbox on the LHS as you look at the front of the car. I removed this because it helped a tiny bit removing the EGR cooler. That has a 10mm nut, a torx screw, a big jubilee clip and an electrical connector. The front part of the intake slides up but there's a little clip that needs to be pressed in to release it.

I then drained the radiator (red knurled screw on bottom of radiator). It did fill up the undertray rather a lot so I really should have removed that first, but it hosed out OK.

Now disconnect the vacuum hose to vacuum pump connection. Single torx screw, pull out 1cm, whilst flexing engine bracket (carefully) with big screwdriver.
Remove EGR thermostat: jubilee clip (NOT the quick release unless you want the thermosat in pieces) and 2 x 10mm bolts. Ideally fit new O-ring (yellow one) when refitting the EGR thermostat, it's not supplied with the Thermostat.



Now remove EGR cooler:

3 x hex bolts.
Jubilee hose clamp underneath.
Loosen clamps at EGR cooler and EGR valve (gives a bit of helpful movement).
Now the fiddly bit, two T45 torx screws into the exhaust manifold. The bottom one is impossible to see but you can get a driver on it OK.
Loosen these but be very careful not to drop them - they're stainless so a magnet won't get them. I used some long surgical forceps to carefully fish them out.
To remove the EGR cooler involves a bit of firm tugging because the exhaust heat shield wraps round the clamp to the exhaust manifold and needs slightly bending out to give enough room to get the EGR cooler out. Don?t be too gentle or there?s not enough room when you need to get it back in!


The EGR cooler is metal to metal seals all round ? no gaskets ? but I cleaned all the surfaces up with fine wet and dry.

Now you have easy access to the main Thermostat.

4 x 10mm bolts
2 x quick release clips

New thermostat comes with new gaskets built in

I needed to loosen a fixing bolt (10mm) under the EGR valve to get enough movement on the rigid plastic coolant hose to separate the joint.

Now replace the thermostat and carefully put it all back together.

I used insulating tape to tape the T45 torx head screws for the EGR cooler to manifold to the torx bit on my socket set. That gave a bit of flex to the screw but held it on the driver. This made fitting those screws fairly straightforward once everything was lined up. The torx driver and tape came away nicely once the screw had taken. Too much tape on the second screw separated the torx driver bit from the extension rod but was fairly easily retrieved.

Filling it back up needed 7.5 litres of 50/50 BMW coolant and distilled water, so buy 3 x 1.5 litres of the neat stuff from BMW.

Bleeding takes a while and the coolant level will go down over a couple of journeys as the air works its way out.

Where I could find torque settings e.g. for the EGR cooler to exhaust manifold and EGR thermostat to EGR cooler they were all 8Nm - which made things easy.

There all done. Being very careful indeed (and figuring out stuff as I went along) this took most of a day. Probably half a day having done it once.

It took me two hours to do this procedure!!!!!!!

Thanks again everyone!

Dandle

Right I did my thermostats today but I didn't get any pictures, sorry about that but I just didn't have time with it getting dark.

The whole job took me 2.5 hrs and Its pretty much as the guide above states. The only things I did differently were that I didn't remove the EGR cooler, I just undid the three allen bolts holding it in place and the flex pipe to the manifold has enough give that you can move it out of the way to get to the top 10mm main thermostat bolt and also replace the egr thermostat without disturbing the vacuum pipe.
I used about 5l of coolant to refill the system so only needed 2 bottle out of the three I bought from BMW. The under tray is worth removing you dont even need to jack the car up, It has three quick release philips head screws on each side and take about 4 mins to remove. Also When the pipes come of the main stat a lot of coolant still comes out of the system and will pour straight onto the alternator so you need to cover it or if you use rag have lots of it.

My car now runs at 91-93 degrees just around town which it never did before, it only used to get to that temp on the motorway and was about 88-89 around town. Makes me thing that maybe the exhaust thermostat wasn't right from the start.

pcy

What is an "EGR thermostat"?

I only know about 'coolant thermostat' or simply 'thermostat'. Essentially, it's a valve opens/closes depending on the temperature of the coolant.

Dandle

On modern diesel engines the recirculate a small amount of exhaust gas back into the intake manifold. Through an Exhaust Gas Recirculation valve (a fair amount of petrols also have EGR systems too). Because the exhaust gases are so hot the go through an EGR cooler, this also has a thermostat on it that opens to let coolant in to reduce temps. If the EGR thermostat fails the car wont stay quite as cold as a main stat failing but still won't run at the right temp.

Dandle

Just an update on my running temps. The car is now running at 93 degrees if driven around town and on a prolonged motorway blast with the revs around 2k rpm it runs at 95 degrees. Seems my car has never been running at the right temperature since I got it at 8 months old.

dkeenan

It's the black item in the bottom picture I put up. It has a plastic cross head screw on it.

ta201ace

hi everyone, my car(525d) is running very heavy on fuel, its running about 20mpg. i have cleaned and checked the egr valve. i don't know were the thermostat for the EGR valve is? can anyone show me were that is?... i checked what temp my car is running today( i checked it using the hidden menu ) and its running 98 degrees around town... is that ok? i was thinking of replacing the main thermostat but don't know if i need to? has anyone had the same problem? can anyone help? cheers

Anzafin

This is EGR thermostat and it locates near the EGR valve in front of the engine.
That 98 degrees must be celcius, right. I'm sure both thermostats work because that 98°C is hot. How's the coolant level? Old oil in engine?

- Antti -