Cause of Airlocks..

[Davenotouring]

Hello!

IS there any other way for an engine to get an airlock other than a cracked head?

I drove my Sport down the road and it quickly got too hot. There was no warm air through the blowers.
I then played about for a while with the bleed screw and stuff, for about 70 miles there was hot air, and the temp was normal, it did seem to get hot when stopped/going very slowly.

Anyway, all was fine, then all of a sudden, the heater started getting colder and colder and the temp shot up. I stopped, undid the bleed screw slightly and loads of pressure/steam came out....

Anyway, got the car home. Just wondering, if it 100% a cracked head, or can an airlock come from something else?

Thanks!

[Ziggy]

No idea, but you've got another black sport!?

(well it's not, but I still wanna see em!)

[Davenotouring]

Will get pics up tomorrow mate.

Along with explanation!

[Splondike]

Will get pics up tomorrow mate.

Along with explanation!

Yeah what's with the Sport purchase mate ? Slippery slope this E30 collecting lark

[Davenotouring]

Isn't it just!

Well, I will take some pics tomorrow.

It was in the for sale section, and a chap was selling it near to me in Brighton.

It has a cracked head and rusty arches, bar that, it's really straight and tidy. Got OBC/LSD/Tech II kit/Tweeter pods!!

It's diamond black like my old one, and it's a 1990 G reg, just like my old one.

I'm gonna slip a new engine in after my exams, speak to my bodyshop guys about sorting said rust and see what's what. Just gonna play it by ear.

The guy selling, Dan (Dodd) is a great chap, good to meet him. He wanted rid as he had nowhere to keep it and he's after a new motor.

I got it for a very good price so I'm a happy bunny.



Like I said, pics tomorrow!

[jonmsm]

hi there,
I am having issues with an air lock on my E28. not a bloody clue where the bleed screw is, but its a pain in the backside cos it causes the coolant to overheat and it just pisses out of the pressure release as the steam created by the airlock forces the pressure up... then i get left with no bloody coolant. how do I get round this cos its driving me nuts, its even managed to blow out two rad hoses in the process!!

[Davenotouring]

On e30 M20 engines, the bleed screw is an 8mm screw which sits on top of the thermostat housing....I dunno if it's the same on yours.

Run it from cold with the expansion tank lid off, and the bleed screw loosened. When Coolant comes out in a flow, do it up. Once the car is up to normal temp, undo the screw again, let the air come out, once it's flowing out, do it up. This should rid the system of air.

The locks could be caused by a crack in the head, which is what I suspect the problem is with this 325 Sport.

[Toby_Unna]

watch it, don't overheat it!

the bleed screw is on the thermostat housiign at the front of the engine on the inlet side.

you should always bleed it if it boils/leaks the coolant out, otherwise it'll get too hot and do the head gasket in.

[Davenotouring]

Hmmmm.

I'm just wondering if there could be any other cause for air locks 'appearing' in the system other then a crack in the head, unfortunately I doubt it, but I'd be happy to hear suggestions!

Toby, how do you fancy some welding on my new aquisition for some beer tokens?! (quite a few beer tokens I'm sure!!)

[Toby_Unna]

no problem dave

you have much respect for possibly having even more cars than i do!

[Toby_Unna]

my mr2 used to get air into the cooling system, i was convinced for ages the hg was going but eventually it turned out to be a leak on the long cooling pipes (front rad and mid engine) i never worked out how air could get IN though.

however bmws seem to run the cooling system at higher pressure than that mr2, when the mr2 had leaks, water just dripped out even with the engin hot, whereas on all my bmws if you get a small hole you get spraying water/steam coming out.

if there's a different problem with the system (water pump/blocked rad/small leak/thermostat/visc fan etc) which is making the engine overheat a bit, and the coolant boils in the engine, then you'll get a bit of air in there which might then cause an airlock and poor coolant flow leading to more overheating and air?

might be talking complete crap though!

[Martinaston]

If the car has the heater matrix with the plastic valve rather than the aluminium one BMW sent a letter to all owners a few years ago and offered to check the car over for free. What they were actualy doing was changing the cooling system filler cap to one with a yellow centre on the underside that said 140. This would release the pressure at a lower setting than the original and stop the heater valve from rupturing and spraying coolant over the drivers feet (left hand drive) but this never cured the problems that made the car overheat in the first place.
What they should have done is replace the heater matrix but this involves taking the dashboard out and removing the heating system, a 5 or 6 hour job (the tight ba****ds).
You can tell if the heater is leaking on a cold day because the windows will steam up.
As the weathers warming up the best thing i can say is to have a root around in the passenger foot well and maybe remove the centre consol and have a look at the heater pipes where they come through the bulkhead.
Other than that boil it up and look for steam.
Good luck

[Davenotouring]

Cheers for the advice chaps.

Does look like a new engine job, but that is what I expected so I'm not complaining.

Toby, might be in touch soon!

Cheers mate!

[jonmsm]

Toby mate,
Have you ever played with a Mk2 MR2. I spent all of today trying to get the air con belt tensioning pully off / loose so I could fit the new belt and failed, its got to be the tightest work space ever - damd Japs!! LOL

Thanks for the info on the bleeding, mine is the M30 engine but I am sure it cant be in much a different place.

[Toby_Unna]

nah never been near one

just keep trying! and be grateful you're not trying to do a headgasket, that really is not a fun job on a mk1 (i've done it twice, obviously didn't do too good a job the first time cos it only lasted 20k miles!)

they are a bit of a sod to work on, all the bolts seem to be twice as tight as you expect them to be!

[jonmsm]

fun and games. I think if the option comes up to help my mate Mike with a gasket change on his Mk2 then I might just be 'busy' LOL!