E34 M20 cooling system bleeding proceedure?

[Valvebounce 2]

So my nightmarish ordeal with my E34 is potentially at an end.

A car I bought as a non runner, then got runing only to find the head was cracked, then had my Ebay head gasket set purchase not turn up, then had to swap everything from the cracked head to another one and put the car back together is all done. I was pleasantly suprised with the sonofa whore even started with minimal cranking.

I elected to replace the radiator with a nicer one, since I got it for next to nothing, and mine had a stripped air bleed bung.

fitted that up today, and filled up to cooling system with water, sans thermostat. (I wanted to try a flush some of the oil residue out of the block which was forced into the cooling system via the cracks through the cam bearing tunnel)

I ran it for a bit, with the garden hose in the header tank. Cracked the nipple on the t/stat housing, and opened the air bleed on the radiator. Ran it for a bit, giving it a few revs. (some crap floated out of the air bleed on the rad) Closed them up, and checked the temp gauge.

It was registering a little bit on the gauge. But the heater was stone cold.

Shut down the engine. And fitted the new thermostat I'd bought for it. (After so much heartache and misery, I'm not taking any chances) Did the same again. Closed up the bleed ports, and went to a tutu around the block. The gauge got up to a gnats cock over halfway. But the heater still only blew stone cold. It feels like the hose from the water pump discharge port that runs up over behind the distributer doesn't have any water in it. give it a sqeeeze, and it really only feels like it has air in it.

When I bled it up with the cracked head still on it, the heater worked mint as.

Anybody got any advise?

I DO NOT want to root this head too.

[hotwire 352]

M20's can be a bitch to bleed.

Firstly - make sure the heater is set to hot. So as to allow water to bleed through the core

Open the bleed screw.

I 2/3 fill the system, start & allow to run up to temperature - thermostat open. I find this tends not to create air locks.

Once up to temp - top up allowing any air to bleed out of the bleed screw.

Recheck when cold. This always works for me

[polley 916]

Jacking up front of car so it is higher can help as well.

[will 169]

Drill a 3mm hole in the thermostat outer ring at the top. Also, make sure the thermostat is installed the correct way up. (There is normally an arrow indicating up..) The hole will assist air to escape into the radiator area where it will easily bleed off. Thermostats used to come with this hole, not sure why some don't..?? This small hole will not affect the overall performance of the system.

Loosen off the hose clamp on the small upper heater pipe and wiggle it around to release air. Clamp it up when you get only water escaping, then continue bleeding in the same manner around the motor if you think there is still air in other small diameter pipes. Normally, clearing trapped air from the heater upper pipe will sort it out though.

As Troy says, jacking up the front of the car will help bleeding stubborn systems. Also, don't forget to put the heater on full hot when bleeding..

[Valvebounce 2]

I had another go, and the head broke clean off the bleed screw in the rad.
scored another one today ($9.20 inc gst) and filled it with anti freeze. Took my time untill I has dead sure all the air was out. The heater only went warm after I drove around the block a few times. I'm quite releived actually.

It hasn't had a wof since 2012. With a bit of luck that might change this week.