Missing Coolant Help

[itdnwiwbp]

Hey, guys. A few days ago my wife noticed her low coolant warning light on so she stopped and had the car towed home so I could take a look at it. There were no other warning lights and I have no reason to believe it's ever been overheated. This morning I took off the plastic pan under the engine, topped off (it took about 1/4 gallon) and bled the system. Wiped everything down and looked for leaks with the engine running for awhile. I was expecting to see something coming from the expansion tank because when the cooling system was overhauled a couple years ago that was the only part my shop overlooked (hence a portion of my recent motivation to start doing as much of my maintenance as I feel comfortable with). I didn't find any leaks. The car didn't overheat or anything but it wasn't blowing hot air with the heat all the way up (though I'll admit that my brief time spent with the car due to traveling and living in SD I don't know all the nuances of the AC/heating). I think I've hit all the details but I may be forgetting something. I've done my homework and think I've covered my bases but I'm still nervous that I don't know where that coolant went. Would it be beneficial for me to invest in a pressure test kit to make sure it's holding pressure or is observing for leaks for awhile sufficient? Anyone have any insight?

[3ZHP]

I just did a complete coming system overhaul and when I checked it after it was at running temp, I found a dripped in the lower hose temp sensor. Another common cause is the water pump. The only way to see it, is to pull the water pump pulley and check for sealable coming from the bent hole. FYI; it may only leak under pressure.


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[brettbimmer]

Perhaps you still have excess air in the system which is not allowing the coolant to flow to the heater core. Sometimes just running the car at idle won't allow the thermostat to open for a long period of time thus not allowing any more trapped air to come around to the bleed screw, so that would be my first thought on getting the heat back operational. Also, if the thermostat didn't open up while you were watching it, the coolant would not be circulating completely through the system, thus making your leak-detection difficult. As to the leak, any evidence of dried (white-ish) coolant on any of the components? Sometimes you can even see it on the underside of the hood if it was shooting upward.

[LivesNearCostco]

Some less common places to lose coolant are heater core, heater hoses, and the two hard plastic coolant pipes bolted to the engine block. If heater core you should see/smell coolant in the passenger cabin. If heater hoses, should see leak on left (driver's side) of engine as the hoses run from ET to water pipe to heater core (3 hoses connected at firewall), and heater valve (right behind/under air filter box) in some order.

If water pipe, that's under the intake manifold and hard to see. I suspect I've got a slow leak there where one of them enters the block, and have a new water pipe and other hard pipe waiting to go on at some point, but I'll have to remove the intake manifold to replace them. I think that's typically a high mileage failure--my car as 192,000 miles. Assuming your car isn't that high mileage, much more likely to be water pump or fan switch temp sensor in the lower radiator hose. Or if ET wasn't replaced, then ET might have crack that only leaks when the system is hot.

Worst one is coolant leaking into oil system or pistons throw failed headgasket, but then your oil should show milky or see whitish smoke from exhaust.

[itdnwiwbp]

Thanks for the ideas guys. Especially the warning about overfilling the expansion tank. I'll make sure the level is good then take it for a drive to get it up to temperature, make sure it's bled properly and recheck for leaks. The water pump was replaced not long ago but I know that doesn't mean it's not a possibility. There's not smoke and the oil looks normal so there's no evidence at this point that it's a head gasket - fingers crossed that continues to be the case.

[mLuMaN83]

Thank you for this thread. I checked my coolant level last week and it was a bit low. I totally forgot about it but you just reminded me.

As far as being OT, these guys pretty much covered it.

[BCS_ZHP]

Jack up the front end to give the air pocket a better chance to flow forward/up to the ET. Then crank it up, turn on the heat and run until the coolant bubbles out of the bleed screw.

Also, look at the rubber on the bottom of your ET cap. If it's indented, has a permanent impression in that rubber gasket, then the cap seal may be bad. A new cap is about $10-15, try replacing that. I've had great success with mystery/unexplained coolant loss and replacing the ET cap.

[itdnwiwbp]

I drove around a little bit this afternoon and didn't have any issues. Heat works fine and I didn't see any leaks anywhere afterward (which bothers me). I'm gonna take a longer drive tomorrow and keep and eye on it. Thanks again for the help, everyone.

[3ZHP]

You can rent, buy a pressure checked or pay to have it done. I did that a few years ago. Went to the great dealership I purchased the car from in northern OH because of a time constraint with work and school. The check was less than $100 and that was a lot less expensive than a catastrophic failure.

Turned out to be that water pump and the tech little John less than 4 feet tall had removed the fan, belt and pulley to find it. I told him I had just done one on my wife's 03 325CIc that had a bearing failure on the hwy. "can you put it back together and tiro a new pump and coolant in the back seat". Little John: "sure no proem, it will ready in about 15 minutes". And that by far makes them the best dealer I've ever worked with.


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[itdnwiwbp]

As I said above, I know that having had my water pump replaced fairly recently doesn't disqualify it as the problem so I will keep an eye on it. I was thinking about buying a pressure test kit if I can't see any other issues in the next couple days. If it is the water pump is leakage fairly obvious from the weep hole during a pressure test or is there just residue?

[BCS_ZHP]

And if the pressure test shows no issues, remember that the ET cap is not a part of the pressure test. That simple part has cured several coolant loss issues for me, and others. If the rubber gasket is over compressed and going bad, it's leaking when the coolant is at vaporization temps so you never see a residue sign on the ET itself.

[itdnwiwbp]

Cool, thanks. I'll keep the cap in mind too.

[danewilson77]

Jack up the front end to give the air pocket a better chance to flow forward/up to the ET. Then crank it up, turn on the heat and run until the coolant bubbles out of the bleed screw.

Also, look at the rubber on the bottom of your ET cap. If it's indented, has a permanent impression in that rubber gasket, then the cap seal may be bad. A new cap is about $10-15, try replacing that. I've had great success with mystery/unexplained coolant loss and replacing the ET cap.

+1

Could also replace with the Al cap from GAS.

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[swingwing]

How many miles on this car? You mention a recent WP replacement; how about the other major components like thermostat, expansion tank and radiator? I'm on my eighth Bimmer, and hands-down the weakest link in these cars is the cooling system. Replacing the major pieces prospectively and doing regular coolant services with BMW fluid is the only way to avoid problems IMO.

[itdnwiwbp]

I'm just shy of 137,000 miles. T-stat, radiator, and water pump were replaced at 115,786 exactly two years ago.

[swingwing]

I'd go along with new ET cap, then keeping watch on it. My current car had a cooling system refresh a couple of years ago by PO; couple of months after I got it, it started leaking coolant. Finally found it - a small leak in center of radiator.


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[itdnwiwbp]

I'm probably gonna buy a pressure test kit today. I went out for a Sunday morning cruise in the coupe then checked the ZHP coolant level (and cap) after driving it yesterday. Definitely down a little bit. Cap looked ok but I'll probably replace it just to be safe.

[itdnwiwbp]

After having the engine compartment pretty well apart trying to get a look at every hose and connection and not finding any residue or evidence of a leak I decided to let my indie have a look. He just called to say it held pressure all night and he couldn't find any evidence of a leak either. So, I'll just keep an eye on it. Thanks for all the advice, everyone!

[LivesNearCostco]

all right good news. It's possible you could still have a small leak that only shows up when it's hot, or if the pressure test is done using the ET mouth, then it could be the cap itself (since cap is not there during pressure test).

[itdnwiwbp]

I asked about the cap and they said they checked that, too. Also no coolant smell coming out of the vents so heater core likely ruled out. I guess maybe I was just being paranoid but I know my car a little bit better now and it didn't cost anything so I'll just keep an eye on it in the future.

[stephenkirsh]

I use a tiny amount of coolant over a few months period. Half ppl tell me that's normal. Half tell me it shouldn't lose any. I never know what to believe.

[BCS_ZHP]

If you look at the o-rings on a brand new ET cap, feel them, then compare to your existing, you'll see & feel the difference. Just looking at the existing ET cap by itself, it looks pretty good, you have to compare to a new one.

[itdnwiwbp]

I guess I should have been more specific when I said they checked the cap. They said they pressure tested it and it held just fine. The two o-rings are slightly flattened, not plump looking like on a new one.

[BCS_ZHP]

That slight difference you described, slightly flattened vs. plump, is exactly what I was trying to describe. I'll bet a round of drinks that's where you're losing your coolant. Try a new ET cap and your problem should be solved.

[NoVAphotog]

If you look at the o-rings on a brand new ET cap, feel them, then compare to your existing, you'll see & feel the difference. Just looking at the existing ET cap by itself, it looks pretty good, you have to compare to a new one.
+1

When I first got my car, Bruce and I noticed a lot of residue around my ET. Getting a new cap per his recommendation was one of the first things I did and I haven't noticed any more since. The differences in the gaskets were very noticeable between old and new.

Would definitely look into the G.A.S. ET cap as well, although I went with oem, I've heard good things.