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Old 09-27-2012, 12:08 AM
robertobaggio20 robertobaggio20 is offline
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Originally Posted by vegasbimmer View Post
My M50 has a coolant leak in a very unconventioanl location and I can't seem to get to it.
From all indication, it is behind the thermostat housing at a hose clamp leading to a hose that runs under the intake manifold. It appears that I will have to remove the intake manifold. Would any members that have removed the intake manifold on M50 be so kind as to give some advice on the procedure? Some pictures would help if possible.
It sounds like that's your main coolant hose (has several branches). Are you sure ? I just discovered a simple way to eyeball these things. Set your phone to video mode with the flash on. Activate video...the flash should come on and stay on...then insert it under the intake manifold and move it around slowly, pausing near locations where you suspect the leak etc is located. Then withdraw, stop video and replay. You might see something very interesting.

In any case, if it is your main coolant hose, then you do have no choice but to remove your intake manifold. This is a time consuming affair, but it does give you some important benefits by enabling easy access to an otherwise congested and well hidden part of our engine. You should take advantage of this to consider the following work as well :

1. You can replace your starter with new one easily. Either that, or you can have your existing one removed and rebuilt. A busted starter is not common but it does happen and this is a no-start situation. If you are keeping the car for the long term, it is worth investing in this imo....should run you anywhere from $150-$300. Only use a Bosch starter. Rebuilding would be cheaper but more time consuming...a straight replacement can be done on the spot by purchasing the new starter beforehand. Use only rebuilt OEM starters.

If purchasing new, ensure that the new starter fits into the bracket vacated by the old one. They might not exactly as BMW started issuing smaller starters for our car later which mysteriously possess the same part number (I had to go return my new one and rebuild my old starter instead). In hindsight, I could have fashioned a new bracket, or drilled a new hole, in the new starter and got it to fit but I lacked the skills, confidence and time at that time.

2. Replace the entire octopussian main coolant hose with a new one. It will rupture eventually. A new hose is a mere $50 or so but the peace of mind you get is priceless. Use new hose clamps as well...make sure they are proper hose clamps that will not cut into the hose when tightened.

3. Clean out your idle control valve. It will be really easy to access it with the intake manifold off. Google these forums or elsewhere for the detailed cleanup procedure.

3.2 Inspect the hooked tube that is fixed between the ICV and the underside of the intake manifold. If it appears cracked and brittle, replace it with a new one....$20 max. This is a possible source of vacuum leaks and so requires inspection.

4. There's a small and thin vacuum hose fitting that connects somewhere near the throttle body and somewhere near the vanos unit. It is cheap. Suggest that you replace it. There's also another vacuum hose that connects from the throttle body to the fuel pressure regulator. It is also cheap. You can replace that as well. These two are not really essential but its fun.

5. Your throttle body gasket is likely to rupture. Its best to have a new one standing by. Precautionary thinking suggests that you should use new intake manifold gaskets as well but I reused my old ones with no mischief to the engine, so its up to you.

6. Your intake valves will be visible once the manifold is out. Take some pictures for posterity, and do some cleaning with a carb cleaner especially if it looks like hard carbon seems to be coating the valves. You can spray carb cleaner or fill with ethanol and leave it for an hour or two and respray again. If needed, use a thin blade to GENTLY scrape off the bake on crud if you can. If it does not come out, abort and do not use extra effort as you'll likely damage something. After doing this, you'll need to remove the spark plugs and crank the engine with the sockets open to expel any unevaporated solvent...this is the safest thing to do. You can help this out by using a hose to physically blow into each intake valve. And of course since the plugs are out, if they are not lifetime plugs, its a good idea to plonk in a set of Bosch Plat+4 4 claw platinum plugs.

7. Take a good look at everything that you see there and with a view to spotting any problems, especially leaks.

8. Give that portion of your engine a good wash after a good soak with a degreaser.

9. Inspect your fuel hoses, especially the little ones at the fuel pressure regulator area, and replace them with new ones if suspect.

10. You're removing your fuel rail, so it would be a good idea to lift it up by tying it to the bonnet with something and then cranking your car to see how the fuel streams out of each injector (if you don't have a friend to assist you). Familiarise yourself with how it should look via youtube's many videos. If anything looks suspect, remove and clean or replace the injector concerned. Or if you know how to bench clean your injectors, do so anyway. Disable all the ignition coils before you do this test, you don't want stray spark when fuel spurts out onto the engine proper if you do this test.

11. If you have not done so in the past 4 years, change your CPS. It is a long term sudden failure item that leads to no start situations and is common in our car. Get an OEM one for $80. It would be an absolute breeze to replace this with the intake manifold off.

12. If you find this list useful, plan everything out carefully and set aside an entire day to get this done in a well lit, well ventilated area, with good friends, music and chilled german ale handy.

13. All procedures should be scanned through the Bentley manual first before you proceed.

14. For good measure.....have your alternator checked out at a battery shop. If it is not performing perfectly, this would be the time to plonk in a new or a rebuilt one, as access will be really easy. It wouldn't be a bad idea to have your existing one rebuilt anyway but that might be a needless expense and alternators tend to go bad slowly and give you clues along the way so it might not be an urgent matter. However, bear in mind that this is a 20 year old vehicle and its best to stay ahead of the breakdown curve wherever possible, even if that means you're spending a little bit more. This is particularly relevant if this is your daily driver.

If you choose to get a new alternator....purchase an enhanced HD alternator. My alternator was 140amps stock. I've now got a 240amps souped up one in there that was also rewired while it was being rebuilt. My car performs like a rocket when I floor the accelerator. Probably the best upgrade I've done for my ride. Have not posted it here as yet as its merely 2 months old and I need to do other things, but since this has come up...

An enhanced alternator will require an extra high-tension wire to be added between the battery and the alternator to hand any additional loads it may bear in future. Simple welding cables (6 ft) with connectors will do the trick, and with the intake manifold off, it can be installed with ease.

15. Do anything else if it is worth doing and if it is easier with the intake manifold off.

Its a long list but I speak from experience obtained over more than one occasion where the intake manifold had to be removed for repairs.

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