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vegasbimmer 09-26-2012 11:47 PM

Coolant leak - Intake Manifold
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.

paperplane94 09-27-2012 12:13 AM

This ain't bad:

robertobaggio20 09-27-2012 01:08 AM


Originally Posted by vegasbimmer (Post 7099166)
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.


vegasbimmer 09-27-2012 03:47 PM

Roberto, I have seen many times when you have helped people in Bimmerfest and I appreciate your input to my dilema. I can actually see the drip at the clamp under the intake manifold, but I can't afford to make all of those corrections right now. I just want to get the intake manifold off and back on after I replace the coolant hose or clamp, replace gaskets and clean whatever is needed.

Paperplane94, thanks for the E-36 procedure from PelicanParts link. How close is this to E-34? Does anyone know?

robertobaggio20 09-27-2012 08:37 PM

Hi Vegas

That was just an ideal list based on the fact that the intake manifold is a big deal to remove, and makes so many things easy to do once it is out. You don't have to do it all of course.

The m50 engine's setup compressed many things together (and yes the writeup for the E36 is the same as the E34 provided its for the same m50 engine). You're going to pay the same amount in terms of time and/or money to remove and reinstall it, so it makes sense to avoid duplicating efforts and eliminate future risks. I mean, I'm sure you did pretty much nothing to even accidentally provoke the leak that you've spotted. How did it get there then? The car is old. Many things in our car were not made to last for 20+ years. We have to stay ahead of the curve out of necessity.

At the very least, clean out your idle control valve. This just requires 10 minutes and some carb cleaner ($8/can). It will smoothen out your idling or at least prevent it from getting worse. Depending on who you speak to, the ICV needs to be cleaned once every 6 months or once every year. Third, at least check on your fuel injectors as described above, since you'll be removing the rail anyway. It will only take you an additional 10-15 minutes and at least you'll know if there's an impending problem. The car does not always throw codes for buggy components and its cool to see your own car's injectors in action. Fourth, take good closeup pictures of each of your intake valves for inspection later. Takes less than 5 minutes, and they will probably look very good not to worry but its fun to have pictures. 5th, do a 1 second hard spray of carb cleaner directly onto each intake valve as soon as the manifold is removed even if the valves look good. By the time everything is reinstalled, any excess cleaner would have evaporated out of the intake valve area, and the carb cleaner will dislodge the looser carbon bits which will become expelled once the engine starts running. So this takes 6-7 seconds total. 6th and imo critical would be you replacing the CPS. If you do not do this now (and have not ever done this), you will regret it later as old ones fail unexpectedly and leave you stranded without a functioning engine literally anywhere and at anytime. A very common no-start issue for the E34. $90 and 5 minutes work when the intake manifold is off, even if you have big hands :). Not doing this means you are taking a bad risk imo.

The starter and alternator would be nice but not strictly necessary they are generally good risks to take. However, if I were you, I would have that alternator checked at a battery shop. It takes less than 5 minutes for them to put it through its paces and the service (along with the battery's reserve charge check) is also free. If a problem is spotted, at least you'll have the opportunity to decide if you wish to get to it at the same time as when you replace your main coolant hose.

Top up your coolant at least once every day, keep spare water in the trunk, and keep an eagle eye on your thermometer while driving until this problem is fixed.

And very importantly (unless you are a very seasoned DIYer), please do give yourself plenty of time to do this. It is potentially stressful and stress tends to generate unforced errors, compounding the situation.

Cheers, Roberto

My525iT 09-28-2012 02:37 PM

Is it hose number 7 connection behind the tstat?
If yes and you think it is just the connection point. You may be able to reach it by removing the air intake and the alternator.
Alternator isn't that fun to remove - however better than messing with the Intake Manifold. If it is the whole hose, then you will need to remove the manifold. Either way the Bentley has it all described. If you do remove the manifold you will need to gaskets, flange nuts and torque them proper.

vegasbimmer 09-30-2012 02:48 PM

I believe the leak is at the connection at hose 7 behind the thermostat so I'll give your suggestion my first attention. Thanks 525iT.

I will report back to this thread when I finish.

vegasbimmer 11-15-2012 11:09 AM

I am finally in the process of removing the intake manifold to replace the 4 way coolant hose.

luckydog 11-15-2012 06:31 PM

I have a good used multi port hose if you want. I have seen the results of small hose 15 split at the block connector and the owner ruined the engine driving on a overheat. I would add a a light silicone sealant on the old gaskets on intake to block.Maybe clean the idle control valve wile there.Final throttle linkage adjustment necessary.

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