coolant goes by by

losing coolant, not in oil or leaking. Smoke when start up and after slowing down to stop. It did over heat a bit when rad went out. Thinking head gasket but oil is clean. Any thing else to check before removing head for rebuild ? 1998 528i

wrong car , sorry. 1998 528

checked all the cooling system hoses for cracks?

That had my car smoking. I popped the hood and saw coolant shooting out causing smoke. Hang on smokes as in tailpipe or hood

Originally Posted by danmar

losing coolant, not in oil or leaking. Smoke when start up and after slowing down to stop. It did over heat a bit when rad went out. Thinking head gasket but oil is clean. Any thing else to check before removing head for rebuild ? 1998 528i

Given the complexity and cost of a head gasket I'd check a few things first, perhaps with help from a repair shop with specialized equipment. Unless I could confirm a head gasket failure between coolant & combustion, I'd look hard elsewhere first. It's possible that the smoke you mention may be a second issue of oil smoke due to valve stem seals or piston rings.

If suspecting a coolant to combusion cylinder leak one can test for the presence of exhaust gases in coolant.
A) One method checks the coolant with strips or test liquid addition to a sample for colour change.
B) Use a tail pipe emissions probe in the throat of expansion tank to test for exhaust gases while engine is running, which should not be present.
C) If you have a sensitive nose, sniff for exhaust smell at the expansion tank, cap off, while the engine is warm and running. But only a few sniffs - be careful of ethylene glycol poisioning.

If chasing a slowish leak, keep in mind that smaller leaks may never leave a drip or wet deposit. The leak can be small/slow enough that the coolant evaporates/dries before forming a droplet, or open only when the system is hot & under pressure and thus lose coolant as a small jet of steam rather than a wet dribble. In either case there is very little indication of the leak point, although BMW coolant does tend to leave a white deposit.

One can use a pressure tester on the expansion tank and look for small leaks, often in a difficult to see obscure corner or hidden location. One can also add ultraviolet dye to the coolant, drive a day or two and then check for dye deposits with a UV light. Again the leak may be in a hidden corner but the UV deposit is ofter easier to find than a liquid seep.

+1 on what RDL said.
Also, check and see if the gaskets around the WP & T-stat are still OK.
Also, once the car is up to operating temp, I would pull over and pop the hood. If you have a friend, I would ask him to rev the engine as well while you check under the hood. That might show the leak.

Another culprit that will make a car smoke is a failed CCV, which in your case might be coincidental, but making you chase a different demon.

Seems like a head gasket to me. Those 6 cylinders seem more susceptible to headgasket. I don't claim to be an engineer but I will guess it because the 2 headgasket not one

Water gone within 40 miles and for sure not leak as it would show. Smoke has sweet smell and burns up at speed but not at low RPM. Done head rebuild before on another similar BMW engine so will just tear down and do this one also. Was hoping there was a simple common solution but I needed to ruin a few days anyway,,,,,,,thanks all.

I say get your cooling system pressure tested and take it from there. Report back on your findings

285,000 miles on the engine with nothing but waster pumps and oil changes so unless there is a common leak issue in the intake area I might as well tear it down. Valves will be loaded up with crud by now anyway.

I will update what turns up as I roll along with it.

How much coolant are you using and how many miles between additions?

Dealing with a sudden leak on my 97 right now too. Started literally overnight. Mine is under the intake it appears. Pulling the intake now to try to find it. I suspect the heater return hose. I rebuilt my engine in December and replaced pretty much everything except the radiator and the coolant hoses under the intake.

#5 is what I'm hoping my problem is. Never been replaced. The one on the 99 has though.

going through about 3/4 gal every 50 miles. Just enough to turn on the overheat light. I will check for leaks once more but not counting on it being that lucky because of the smoke when slowing down.

OUCH!. That's a lot of coolant.
I think you can stop looking for leaks, unless you're smelling coolant under hood.
The good news is you've got an iron block so head bolt threads are OK. Bad news is M52 heads are known to crack on overheat. It would be useful to find out which cylinder is leaking coolant, if possible, before pulling the head. This will help with head inspection. I'd pull plugs and pressurize cooling system, and see which cylinder fills with coolant. HF has a coolant system pressure tester for ~$60. Keep us posted.