Replacing Thermostat Waterpump Coolant... Procedure.

[e34.535i.sport]

Replacing Thermostat and Waterpump... Procedure.

TIME: First time - took me and the Captain 4hrs factoring in a hail storm and some good old rain.

COST - Approx £70-£90...

First of all I've grouped these three things together because if your doing one I'd seriously recommend doing the lot while your there - it could save a lot of time and effort and inconvenience in the long run. You could also change the viscous fan coupling while there if necessary, as well as hoses etc. Coolant should apparently be changed every two years, and i tend to stick to this and use BMW coolant...

Failure Signals:

Thermostat: If your temp guage is acting erratically don't automatically assume the thermostat is to blame... It could be sensors etc that need cleaning/changing. However if your car is taking too long to get to operating temperature or is overheating the thermostat could be to blame. I personally found my car would stay in the blue for a really long time and it was using more petrol than usual because of this (for obvious reasons). I also found that the heating in the car was working before the car was hitting operating temp which should not be the case.

Water Pump: More than likely overheating will occur if your waterpump dies, so probably best to change it as a preventative measure rather than wait until it goes. Particularly if yours has a plastic impeller as this can cause major damage if it does fail on you. In general this is an easy job thats well worth doing when you factor in the life of your vehicle and the price of the pump - you can pick one up with a metal impeller really cheaply.


Tool Requirements

• New Water pump
• New Thermostat
• 4 Bottles of BMW Coolant
• Gasket Scraper
• Ratchet and various sockets inc. 10mm 13mm 19mm 8mm etc
• Various Screwdrivers (flat and philips head)
• Funnel
• Measuring Jug
• Empty containers (for old coolant)
• New hardware (nuts bolts etc)
• 32mm Spanner (widely available in Halfords etc)

Preparation
Not much in the way of preparation is needed for this job, but you will need to remove the front undertray by releasing the four or five 10mm nuts holding it on to the bottom of the car. Due to spills etc I'd personally advise doing this job with the front of the car on a grassy area - saves staining the drive!

Also, familiarise yourself with the parts you will be replacing. The water pump connects directly to the fan at the front of the engine. You can see it best from the passenger side of the vehicle (UK vehicles). Just above and slightly to the side of this is the thermostat housing. Mine looked like a stoney colour and it has a screw sticking out of the top of it. This is the bleed screw... you'll have fun with this later. Inside the housing lies the thermostat - apparently some housings are plastic others are metal. The plastic ones can be brittle so it may even be worth replacing it if yours is plastic. Mine was metal (535i) so I didn't need to replace it as it was in good condition. You will only need to pull of the end of this housing (nearest the front grill) to access the thermostat.

Getting started...
Open the bonnet and have a look around. As a precautionary measure I removed the two drivebelts to save getting coolant and whatever else all over them. To do this you will need to locate the two tensioners that allow you to tighten/loosen the belts. One is above the alternator and the other is underneath the car. It works with a kind of self locking mechanism - you will need to loosen the 13mm nut at the back and then use a 19mm socket to loosen the belt and remove it (Same procedure for both belts). I probably make this sound complicated but its really simple once you have located the tensioners.

If you aren't replacing the belts (probably worth doing - i thought mine were ok until i took them off and found huge cracks all the way around)... note the direction of rotation and try and replace them the same way later.

Making space - Remove the Fan
Very simple procedure... First of all locate the two clips holding in the fan shroud (one on each side) - get a screwdriver behind each one and push them out. Be gentle as I managed to snap mine off being heavy handed... Now get the 32mm spanner and put it on the huge nut near the centre of the fan. You will need to give this nut a knock in the clockwise direction with the spanner to remove it...IMPORTANT - THIS NUT HAS LEFT HANDED THREAD SO MAKE SURE YOU HIT IT CLOCKWISE... Once you have jolted the bolt loose you should be able to turn it with the spanner until the fan comes loose... watch out as it can fall and its quite heavy! Once its loose pull the fan and shroud off (upwards) together. This is a perfect opportunity to replace the fan clutch...

Drain the coolant...
Before you start set your dials inside the car to full heat and remove the radiator filler cap. To drain the coolant locate the drain plug for the radiator at the bottom left corner of the radiator (from the drivers seat) and undo it with a large screwdriver or coin. Be prepared with a large funnel and pan or bucket or whatever to catch the coolant as it comes out rather quickly once you pull the plug out! I found a big funnel with some hose on the end leading into a washing up bowl worked well and prevented mess and drenching the alternator (not wise). Tighten back up the drain plug.

Now i'm going to be honest here... I couldn't be bothered locating the engine drain plug (for coolant) under cylinder 6 so I used a different possibly unorthodox method to get the rest of the coolant out. You will need to take off the small U shaped hose that connects the thermostat to the water pump anyway so I removed that... Simply use a srewdriver to loosen the Jubilee clips and pull. There may be a little mess here but I didn't get much at all. Once this hose is off you will be able to see inside the water pump to some extent - it will be full of coolant. I got a big syphon (I cant spell it for the life of me) and syphoned the remaining coolant out of the waterpump. I couldn't get absolutely all of it but most of it.

Remove and replace the Thermostat
To remove the end of the thermostat housing you will need to remove the hose that comes off the bottom of it (connects to the bottom right hand corner of the radiator - from drivers seat of course). Do this and then carefully undo the four bolts holding on the end of the thermostat housing. There will be two long and two short bolts. These may have been in for a long time so be gentle with them. Once you have removed the bolts pull off the end of the housing - it may be a stuck on so a little force is necessary but be careful. Now you will be able to see the thermostat. Note how it is orientated and pull it out. It will be stiff and require a stern pull... Once it's out give the hole it came out of a good scrape and get any remnants of the old O-ring off the housing and clean it. Now ensuring you have a new O-ring on the new thermostat put it in place and re-attach the end of the housing using new bolts (large = 10nm and small = 8nm I think). DON'T OVERTIGHTEN THESE BOLTS!

Remove and replace the Water Pump...
Have a look at the water pump. First thing you will need to do is undo the four small (10mm i think) bolts and remove the pulley wheel. You may need to use a spanner or something to keep the pulley from spinning while you do this, or you can temporarily put the drive belt back on it... There are six bolts you will need to remove on the water pump once the pulley is off. Two of these bolts are inaccessible due to a banana shaped piece of metal which I can only assume is for protection purposes. Remove this by undoing the two bolts holding it to the engine (10mm and 13mm), and then undo the six water pump bolts (13mm i think). Once you have removed the bolts the pump should come off with relative ease. There may be some mess here so be ready with rags and such. Once the pump is off clean the hole it came from and scrape any remains of the previous gasket off the side of the engine.
Now its simply a case of putting the new pump onto the engine (ensuring the new gasket is orientated correctly). To do this put a couple of bolts through the holes in the pump and gasket and then press it onto the engine... This can be fiddly and annoying. After ten minutes of messing around get the bolts in and tighten them up to 10nm i think which is NOT very tight at all. Then put the banana thing back on and the pulley wheel.

ALMOST THERE!

Now its a case of putting everything back together... First get the belts back on and tighten them back up using the tensioners as before. Then put the hoses that you took off back on and be sure the jubilee clips (hoseclamps) are tight.

Next is the fan - refit with the fan shroud... the reverse of the removal procedure!

Refill the Coolant
Now ensure everything is back together correctly and refill the coolant via the reservoir near the windscreen in a 50/50 mixture (or whatever is applicable to you) making sure you have opened the bleed screw on the top of the thermostat housing first (8mm). As far as I'm aware the system on mine holds approximately 6.5 litres (someone chime in if i'm wrong here please!). When you are getting close to full coolant will flow out of the bleed screw... close the bleed screw and continue to fill until the coolant reaches the correct level on the reservoir and then put the cap back on and tighten it up.

Bleed the System...
I've read many horror stories about bleeding the system but everytime I change the coolant I bleed mine without a problem - no bubbles or overheating... nothing. However you should run the engine once you are happy everything is back together correctly until it reaches normal operating temperature... The upper radiator hose will become hot. Check for leaks around the pump and thermostat housing and radiator drain plug as well as hoses etc. Also check the fan is operating correctly.

Now open the bleed screw on the thermo housing slightly until coolant flows out with no bubbles/air and tighten back up. Repeat this procedure over and over until you are satisfied there is no air in the system at all. If you don't an air pocket can build up in the thermostat making it stay cool and not open... This in turn does not allow the radiator to effectively cool the coolant and the engine and overheating will undoubtedly occur (Not good). It is suggested also that you repeat this procedure on a steep incline (nose up) to help the air to travel to the thermostat and escape when you open the bleed screw. Always keep the dials inside set to full warm too whilst doing this. Hopefully like me you won't have a bleeding problem and you can enjoy some worry free driving for a while!

Many thanks go to CaptainGoSlow for assisting me in the wonderful hail storm we were blessed with

*I hope this is useful to newbs like myself - I in no way mean to patronise anyone or suggest this is the perfect way to do this job... because it probably isn't! However if I can do it successfully using this procedure I'm confident anybody can...

**I will try to get some pictures on but I find it difficult to find time... If anybody has any to throw on please do.

***Thanks to all you guys who give me advise on the job in the first place I was a bit apprehensive about it but rather enjoyed it in the end!

****Any questions or if I've missed anything PM me and I'll see if I can help you out in anyway?!

[genphreak]

Great write up. Just a few things tho...

1. Big warning: Use the right coolant (BMW/Volvo/SAAB Blue OE coolant is only choice for me as the 2 of 300 US Brands that otherwise fit are not sold elsewhere)
2. Don't leave any old stuff in there as it will crystalise no matter how little is left. Have the courage to get under and remove the block drain. You don't even have to jack the car...
3. Flushing the block and radiator is a real good idea with the cabin heater on hot.
4. If you have trouble bleeding, your bleeder may be blocked. Sometimes the pin on the bolt cracks off after you open the bolt up. (ie it has corroded into the pin hole it sits in) remove, spike the build up with something thin and sharp (engine cool or you'll get burnt) and reinstall.

[whiskychaser]

You make a very good point about not getting coolant on the belts!! Maybe I missed it but did you mention about keeping the fan upright? I dont even have the same motor but thought it was a great write up.

[e34.535i.sport]

You make a very good point about not getting coolant on the belts!! Maybe I missed it but did you mention about keeping the fan upright? I dont even have the same motor but thought it was a great write up.

Hey Whiskey thanks for bringing that up - I kept mine upright anyway but forgot to mention it... Is it so the waxy stuff inside stays where it should and doesn't leak out?!

[e34.535i.sport]

Thanks Genphreak you make some good points there... I'm interested in this blue coolant you speak of - I bought mine from the BMW dealer and its illuminous green?

[whiskychaser]

Hey Whiskey thanks for bringing that up - I kept mine upright anyway but forgot to mention it... Is it so the waxy stuff inside stays where it should and doesn't leak out?!

Yep. Funny it doesnt leak when its spinning round though

[DDK's 525]

I just replaced my heater core and radiator (don't ask how I screwed the radiator up. stupid plastic ) and I used this bleed method from the bmwE34 website

M20 Bleeding experience by moots:

Just to share a simple method to bleed the cooling system.I really cannot comprehend why we need to bleed,bleed and re-bleed the cooling system after every maintenence.I did this after replacing the thermostat and flushing the coolant:
(Mine's an m20 engine with the reservoir by the side of the rad)
1.Fill up the rad with the plastic bleeder screw(on reservoir) and metal bleeder screw(on t-stat housing),open.
2.When full,put a finger over the reservoir bleed hole and blow,yes,blow into the reservoir filler neck.(we are basically pressurising the system)
3.When water flows out of the t-stat housing bleed hole,tighten the screw.
4.Top up reservoir if required.
5.Now blow again until coolant exits the reservoir bleed hole and tighten when bubble free.
6.Top up coolant to the cold/kalt mark,tighten cap.You're done. No more bleeding required as all air is purged from the system. I have done this 4 times on three cars and it worked like a charm.

But I modified it a little. Instead of blowing in to the tank, I used my compressor turned down to 10psi. I used the blower nozzle and zip tied a 5"-6" piece of bicycle inner tube to it. I then stretched it over the fill hole and pressurized the system and followed the procedure above. It worked great the first time

Btw, I have an m20. Don't know if it will work on any other engines.

[allerston]

i wanna thank all you guys i have learnt so much.everyday is a learning experience for me