JasonH

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.

Anzafin

Thanks mate!

This is great! I will probably need this DIY quite soon as I'm planning to change my main thermostat. I already changed the EGR thermostat but that didn't help much. Too bad you didn't take any pics. They would have been helpful too.

- Antti -

JasonH

Sorry no pictures. I did think about it but I really needed to get the job done and didn't want to risk running out of time.

juanfr

Hi,
did you noticed any benefit with the change? better mileage?
Thanks

JasonH

The car runs a lot hotter - around 92C. Haven't done enough miles yet to work out if the MPG has improved much. When I have some figures I'll report back.

Loz

JasonH, you?re a star, your instructions were spot on, the thermostat is only £40 inc VAT in the UK from BMW and taken me just under 3 hours to complete with the help from a friend reading out your instructions, plus 2x1.5 Litres 50/50 antifreeze (BMW @ £8.50) and 5 Litres distilled water from Halfords (£3.50). Sytners BMW wanted £327 to do the Job!

Be sure you have the correct tools before you start though, you?ll be stuck without a good quality Torx T45 Bit that can take force you?ll need to apply without shearing. I used blu-tack on my bit to hold the screws whilst removing, used tape as instructed to put them back.

Tip, cover the corners of your radiator to avoid shredding your forearms! And remember to tighten the drain plug as soon as you?ve drained the radiator, imagine forgetting that!!

Regards

Loz (535d)

jas_r_1

Was this quite straight forward then?

I want to do it but can't be paying a dealer

gav900

Great write up Jason, i checked my egr and its goosed...so might as well do the main stat as well. I'm wondering if it may be easier to remove and refit the main thermostat from beneath the car (main splashguard removed)?
I'll check out this avenue when i do mine.

Cheers

Gav

gav900

Just an upddate, i removed my front splash guard (front of car on ramps) when i changed my 'stats'. It did make the job easier (drained the coolant straight into a bucket for example) and access to the main thermostat lower hose connection was better. It only takes a few mins extra to remove the guard and i'd say was worthwhile doing.

Gav

kErb

Jason H

Thanks for this - top DIY. I followed your instructions to the letter and it proved a lot easier than I expected it to be. The only thing I did differently was to put a hose clamp on the bottom radiator hose which stopped the rad from draining. When I refilled and bled the system it only needed 4.5 litres of antifreeze / water in total. It took approx 4 hours from start to finish and the car now runs at 89/90 degrees - perfect.