Compression leaking into the coolant. Cracked head? Gasket?

Fri Dec 04, 2015 12:26 am

M20B25. 325 iX.

Car has probably been running with low coolant lever or "air pocket" lately.

All help appreciated. Feel very stupid and sad about this. Love the iX and hate the fact I may have caused this because of neglect.

Today: suddenly hot air ceases to come from the vents. I stop the car and try bleeding the system using the bleeder valve. Plenty of hot gas or steam comes wooshing out and then brownish rusty looking water. The hoses feel overly hard. I try bleeding again and morse steam comes out. Nasty noise starts, guessing from thermostat housing or water pump. Rev the engine a bit and then coolant comes out and noise goes away.

Try filling up with water and repeat the process. Pressure keeps building up. Open the cap on the "coolant container" (what is the english word for this?) and coolant starts gushing out! Redo this a couple of times with same results. Start driving home. During the drive home when coasting or low revs only cold air comes, under load and higher revs warm air comes. At some stage super hot air comes from the vents.

I have read the forums and sounds like I've cracked the head or that the head gasket has blown. This made me reflect on that last time I drove the car it took ages for warm air to start flowing.

How can I diagnose the problem? Coolant looks awfull. Engine has done 180000 km and been well serviced by BMW untill last year.

I'm thinking of doing a flush of the cooling system and put new coolant in or possibly only water to make it easier to see what's going on. Have a good BMW dealership that I trust but want to do what I can myself to save money. I'm OK with spanners, done a few jobs myself like timing belt and brakes.

What is reasonable to pay for a replacement head and what should I be aware when buying a used one?

Edit:

No mayonaisse under filler cap or dipstick, will remove rocker cover tomorrow and look.
Temperature gauge was never higher than between the 12 o'clock line and the next white line. Never close to red.

Edit 2: is there any point in tightening the head bolts a little if there is a leek?

Fri Dec 04, 2015 3:35 am

Could just be a knackered water pump???

I had a lot of weird games with an old 325 that turned out the pump was only really circulating the coolant properly when giving it some revs!!! Only got hot at standstill and only got warm air from the vents when revving!!!

Somehow got away with just replacing the pump on that one, so hopefully you'll get lucky!!!

Mon Dec 07, 2015 2:49 am

Thanks Willnz and miniblob for responding.

Have'nt had time to deal with the car, will update thread tomorrow arter doing some tests.

IF only the gasket is shot am I risking cracking the head if I drive to a workshop to get a leak-down test done?

Mon Dec 07, 2015 2:53 pm

Ok. Not towable being an iX so can't get it to workshop without driving.

Just popped rocker cover: no mayo but plenty of old black, hard stuff on inside of cover. Normal? "Carbon deposits" perhaps?

Will try flushing and refilling with water to see how it behaves and if water goes brown again.

What about tightening head bolts a little. Stupid? [/img]

Mon Dec 07, 2015 6:37 pm

No problem towing an iX as long as all four wheels are on the ground - tow rope, rigid bar, or A frame are fine. It's a 'spec' lift or dolly that mustn't be used, unless you remove the front prop.
What kind of head do your cylinder head bolts have? Hex or torx?

Mon Dec 07, 2015 9:59 pm

could it not be a blocked radiator

Tue Dec 08, 2015 12:25 pm

Brianmoooore: ah, that's right, it's towing with front wheels on trailer which doesn't work. I did however fry the front diff on this car about 10 years ago by coasting down a hill with enginge off. Never got to know how that happened.

Bolts are hex. Risk of snapping?

Scottybeemer: flushed it through yesterday so seems not to be blocked.

Searched abit for a kit to test water for combustion gasses but haven't found one.

Thu Dec 10, 2015 7:30 pm

I believe the kit you're after tests the coolant for evidence of contamination, like this: http://www.ebay.co.uk/itm/COMBUSTION-LE ... SwbdpWWz5M

Thu Dec 10, 2015 9:03 pm

MartinSE wrote: Bolts are hex. Risk of snapping?

The hex. bolts are at risk of snapping, and you should check to see if one has already.
They should be replaced with torx. bolts ASAP, even if the head doesn't have to come off.

Fri Dec 18, 2015 1:44 am

Thanks everyone for input and advice. Turns out the symtoms were probably caused by having far to little coolant in the system. Flushed radiator, block and heater and refilled and could not reproduce the symptoms of gas wooshing out of the bleeder valve.

Did compression test: with engine half warm all cylinders fairly equal except nr 5 which was about 20 % less than the others. Redid the compression test later with engine fully warm and cyl 5 was less than 5 % lower than the others.

Will be monitoring the coolant level closely.

Brianmoooore: Thanks, new bolts ordered.

Fri Dec 18, 2015 10:17 am

MartinSE wrote: Brianmoooore: Thanks, new bolts ordered.

Remove the old bolts one at a time, and fit the new one in its place, tightening to 22Nm. When all the bolts have been replaced, do th 90 + 90 degree final tightening exactly as you would do when fitting a new head gasket.