Coolant Leak Revisited...

[theos]

Posted about a week ago cause I discovered a loss of coolant after using my AC. Turns out that was pure coincidence. After topping off the coolant (about 2 quarts) I drove about 150 miles and again got the check coolant message. Now I've been pretty diligent about spying underneath for leaks. Nothing. Pavement is always bone dry. And I haven't overheated. Can't find any evidence of leaking in the engine bay. Should I now look to the heater core as the likely culprit?

What would likely leak and where during driving, which it seems to be doing? Having a pressure test done tomorrow morning, but any help for you all would be great.

[ESSSupreme]

Check your oil.

[theos]

Engine oil and coolant are both clean. No smoke from tail pipe and it hasn't overheated. I'm also trying to keep optimistic about it not being a HG. I really don't think it is. I've only had the car for a little over a month now and a compression and leak down test came back fine before I bought it. But it is leaking somewhere.

[David325e]

I have my money on Aux water pump. Next step will be it goes completely and car can't run without overheating. Hopefully that test will turn up bad hose, loose clamp, etc.

[darrenforeal]

Also OP you said you got the check coolant message, but when you checked it was it mostly gone? The reason I ask, is because sometimes the sensor can go. That happened to my car. It kept saying low coolant when the car was turned on, but the level was fine. Turned out to be the sensor.

[pennpen]

i have the same issue, oil is clean but my coolant just keeps disappearing without a drop on the floor

[theos]

There's definitely coolant missing. The last time I got the message I pulled in to my driveway and let the car cool over night. It took about a 1/2 quart to fill to the cold line on the expansion tank the next morning. Again, nothing on the ground or anywhere I could see under the car. Had to happen while I was driving. The sensor along with the expansion tank were replaced about 20k miles ago. I know it doesn't mean the sensor is fine, but I'm fairly certain it's not the problem. But I will be checking it along with the cap. It's fun when it's a super simple fix.

[darrenforeal]

There's definitely coolant missing. The last time I got the message I pulled in to my driveway and let the car cool over night. It took about a 1/2 quart to fill to the cold line on the expansion tank the next morning. Again, nothing on the ground or anywhere I could see under the car. Had to happen while I was driving. The sensor along with the expansion tank were replaced about 20k miles ago. I know it doesn't mean the sensor is fine, but I'm fairly certain it's not the problem. But I will be checking it along with the cap. It's fun when it's a super simple fix.


ya, weird probably not the sensor. hmmm...

[h2oyo]

I had a friend that had a leak on the expansion tank hose bib. I know you said you changed it but it would only leak when it had pressure in the system. It would then only very slowly run down the back of head and block. His also didnt show any signs of leakage. Just something to check.
Johan

[530 i]

+ 1 on checking the aux. water pump, especially the inlet pipe which just snaps off as the plastic is very brittle from years of dealing with hot coolant.

The valley pan gasket can produce a slow leak and it is not obvious at first. The coolant will pool at the back of the block and drains through either one of two holes on each side of the rear of the block. It then drains between the engine and transmission and appear at the small opening underneath the assembly.

If the leak is slow the heat will vaporize most of the coolant so do a pressure test on the cooling system, take the engine acoustic cover off and shine a torch down at the back of the block and see if there is any coolant leaking.

In the photo you can just see the small hole which drains any liquid from the rear of the valley.

[theos]

Well, checked everything out today and the results are...nothing. Everything normal. Can't find weeping, let alone a leak. No idea where to go from here other than keep driving until whatever is faulty manifests itself more bluntly. Any other tricky spots I should look into?

[David325e]

Yep, I'd keep driving, keep an eye on it, and wait. I still have my money on the aux water pump or one of the hoses to the heater core thats almost behind the block. Can be hard to spot until they outright burst.

[jehu]

Do you smell coolant inside the car when you first turn on the blower? Can you get the car up on a lift and look at the Transmission Housing? if you see wfhite crusty residue it may be the valley pan gasket which often leaks at the very back of the engine although it would eventually leave a little leakage on the ground which you'd see. I fixed it with a teaspoon of Alumaseal powder in the expansion tank.

http://ww2.justanswer.com/uploads/Arench/2009-11-02_175550_alumaseal.jpg

Add it when the engine is cold then drive it up to operating temp as long as possible.

[theos]

No white crusties. I don't think it's the valley pan gasket, specifically because I've never seen a drop on the ground. And after having it on a lift today I couldn't see any evidence of leaking.

The only time I've smelt the coolant was the first time I got the coolant level message. No smell when I turn on the blower. AC blows cold and holds cold.

I'm leaning towards it being the aux water pump or one of the heater core hoses. But as of right now there's just no evidence. Guess I just have to hope something goes soon so I can know for sure, which is a weird thing to root for.

I'll read up on the alumaseal. Though I can't think it would help if it's a hose that's going?

And thanks for all the suggestions, guys. This being my first BMW and coming from mainly DSM cars, where it's always a blown turbo, you've been nothing but helpful.

[ESSSupreme]

Do you smell coolant inside the car when you first turn on the blower? Can you get the car up on a lift and look at the Transmission Housing? if you see wfhite crusty residue it may be the valley pan gasket which often leaks at the very back of the engine although it would eventually leave a little leakage on the ground which you'd see. I fixed it with a teaspoon of Alumaseal powder in the expansion tank.

http://ww2.justanswer.com/uploads/Arench/2009-11-02_175550_alumaseal.jpg

Add it when the engine is cold then drive it up to operating temp as long as possible.

Please don't add any stupid sealants to your engine unless you want to pay huge bucks at later time.


No white crusties. I don't think it's the valley pan gasket, specifically because I've never seen a drop on the ground. And after having it on a lift today I couldn't see any evidence of leaking.

The only time I've smelt the coolant was the first time I got the coolant level message. No smell when I turn on the blower. AC blows cold and holds cold.

I'm leaning towards it being the aux water pump or one of the heater core hoses. But as of right now there's just no evidence. Guess I just have to hope something goes soon so I can know for sure, which is a weird thing to root for.

I'll read up on the alumaseal. Though I can't think it would help if it's a hose that's going?

And thanks for all the suggestions, guys. This being my first BMW and coming from mainly DSM cars, where it's always a blown turbo, you've been nothing but helpful.

Pressure test your coolant system.

[jehu]

Please don't add any stupid sealants to your engine unless you want to pay huge bucks at later time.



Pressure test your coolant system.


You care to substantiate your fear?

The stuff is perfectly harmless and completely stopped my valley pan leak and I mean completely,not a single drop since.. That stuff is perfectly safe. It has been in for a few thousand miles now with no problems at all. Its aluminum as is the block. It doesn't clot or stick and cause blockages especially in the small amount I used. If we were talking about a fresh engine that you'd expect to be in use for many more years to come then tearing it apart and replacing leaking gaskets and seals would make sense. This engine has around 250,000 miles on it and I am not inclined to spend any more money on it certainly not to have the valley pan gasket replaced.

Please respond with factual data proving this product harms an engine causing extensive repairs to be needed.
Some such additives can clog the heater valves it seems but this product has not done so.

[ESSSupreme]

Please respond with factual data proving this product harms an engine causing extensive repairs to be needed.
Some such additives can clog the heater valves it seems but this product has not done so.

I called BMW of Manhattan when I had a leak and spoke to a master tech there who pretty much laughed at me and told me not to put anything in unless I plan to replace everything later,

You can call your own BMW dealer and ask them. While they might be biased; my car is not a daily beater and I rather not have any 'magic in a can' stuff near it.

Addressing the leak properly is cheaper then replacing the whole system later; again that's just me. If it works for you that's great; I'm very picky what kind of stuff goes in and out of my car.

[jimoreno]

Does the coolant level go back up when you open the expansion tank cap? I had a problem with mine when the recirculation line small hole in the neck of the expansion tank got plugged with something and then the expansion tank became pressurized. I got the low coolant level warning but when I opened the cap it came back to normal. Disconnect and blow some air through it and re-check.

[jehu]

Does the coolant level go back up when you open the expansion tank cap? I had a problem with mine when the recirculation line small hole in the neck of the expansion tank got plugged with something and then the expansion tank became pressurized. I got the low coolant level warning but when I opened the cap it came back to normal. Disconnect and blow some air through it and re-check.


So what do you think got clogged in that pipe? Did you use Alumaseal?