E30 Zone

Can anyone offer me any words of wisdom when it comes to bleeding the coolant on an M20 ?

I had a pipe split between thermostat and water pump, so I replaced this but didn't follow the correct bleeding process, I just did what I've always done on my previous early 90's Vauxhalls etc.

So after a few miles the car decided to blow the top rad pipe off... I got the car home as was only a mile or so away but obviously threw out all my coolant!

I've slowly topped up the system and had the heaters on hot and I loosened off the bleed screw every few minutes or so once up to temperature.

The car has almost taken 10lts of coolant / water... But it still just goes right up to the red on the temp gauge and isn't blowing out warm air.

Does it just take hours to bleed out all the air?

Also, I dont have an expansion tank, but the coolant bottle is kind of part of the rad?? Probably irrelevant though.


Anymore tips or things to check for before I go mad?

as far as I know all m20's have a expansion tank.

Sounds like you have the wrong rad for starters....

joeyb wrote:
Also, I dont have an expansion tank, but the coolant bottle is kind of part of the rad?? Probably irrelevant though.

That dont sound right.... There should be a expansion tank on the nearside of the engine bay...

Are you saying you undo a coolant cap on the rad and fill it from there??

Put up a pick of your coolant bottle incorpoarated rad....

don't know if it's the same for an M20 ....but on the M30 i find the quickest and simplist way is heater control on hot ...... fill up as norm ......from cold ......... at the header/expansion tank........... when your full up.........undo one of the temp sensor thingys at the front and i always fill the rest up there......when it pi55es out, do the sensor back up and away you go. Leave the heater control on hot throughout Always works with out fail for me.......However if you are blowing pipes off etc, that hints at serious pressure in cooling system......possibly an air lock.....hence my bleed procedure .or.......... head gasket probs ..........all the best Gus :0)

Low_E30 wrote:

joeyb wrote:
Also, I dont have an expansion tank, but the coolant bottle is kind of part of the rad?? Probably irrelevant though.

That dont sound right.... There should be a expansion tank on the nearside of the engine bay...

Are you saying you undo a coolant cap on the rad and fill it from there??

Put up a pick of your coolant bottle incorpoarated rad....

Yup, exactly that.

Here is the only pic I have to hand, taken shortly after the rad pipe blew off hence the mess!



I own Tony's old car (Eko on here), that chap really knows his onions so I'd be surprised if the rad on the car isn't the right one, maybe an upgrade ? Probably says on the build thread, I'll dig it up...

Stupid Photobucket upload app! Is that pic working? Can't view it on my iPad...

That looks to me suspiciously like an E36 rad not an E30 rad!

The rad should look as below:



Where in the top left corner of my engine bay (from this angle) is the expansion tank. You can see the radiator has no filler cap on it or expansion bottle.

Also, is it only the rubber pipe that has come free of the radiator top connection? I had an E36 6pot blow the top hose which actually turned out to be it snapping off the top connection. You hose and connection look rather tatty and not that nice, I'd suggest you clean them up (inside of the hose, outside of the connection) to ensure it gets a good seal.

You should probably also change the thermostat as it sounds like yours could be stuck closed which won't aid in the cooling of the engine or the flow of hot water to the heater blower unit.

Check the build thread, i think tony used an e36 rad as an upgrade, but it shouldnt make it any more difficult to bleed.

http://www.e30zone.net/modules.php?name ... c&t=226008

RAD should be correct I posted a thread above yday, it's an m20 rad

isn't there a bleed nipple at the termostat housing?

Have you checked/replaced you thermostat?
Blue temp sensor?
Are you losing water?
Whats for dinner tommorow?
have you checked all the coolant pipes as there could be a block no?

Have you bled the rad from the wee screw next to the filler cap? Get the cars nose up a bit. On a ramp or kerb is good.then try both bleed screws. Also top the engine up via the top hose if needed (when cold obv ).

joeyb wrote:

Low_E30 wrote:

joeyb wrote:
Also, I dont have an expansion tank, but the coolant bottle is kind of part of the rad?? Probably irrelevant though.

That dont sound right.... There should be a expansion tank on the nearside of the engine bay...

Are you saying you undo a coolant cap on the rad and fill it from there??

Put up a pick of your coolant bottle incorpoarated rad....

Yup, exactly that.

Here is the only pic I have to hand, taken shortly after the rad pipe blew off hence the mess!



I own Tony's old car (Eko on here), that chap really knows his onions so I'd be surprised if the rad on the car isn't the right one, maybe an upgrade ? Probably says on the build thread, I'll dig it up...

Are you sure that is an M20?

b12rlw wrote:Have you bled the rad from the wee screw next to the filler cap? Get the cars nose up a bit. On a ramp or kerb is good.then try both bleed screws. Also top the engine up via the top hose if needed (when cold obv ).

Hadn't really noticed another bleed screw... Won't that second one be no different to having the cap removed?

Also, the top pipe gets stupid hot...is that normal? (doesn't appear to have any pressure buildup in it though)

I think I'll try a new thermostat next, as it was the bleed screw was mashed up and a pig to undo.

Ignore my previous post - early morning eyes

With the fact you're running an E36 rad (that is an E36 6pot one and not an E30 M20 one, mine is an M20) I'd suggest you only use the bleed screw on the radiator itself. As has been said, nose in the air and use that to bleed. Removing the filler cap often will alter the water level as too much air can get in.

When my E36's rad blew (and cooked it's head) I could remove the filler cap and watch the water level rise in the expansion tank as the system filled with air. Using the bleed screw avoids this. The reason for it is simple, you remove the filler cap and air can run freely into the expansion tank and then also down the bleed line, pushing the water back into the bottom of the radiator.

Ok cool. Will try that this evening. Will get the front end higher too..

I''ve been running an e39 528 radiator because it's bigger and has the expansion bottle on the side (I'm limited by space) so the e36 one should run no probs, at the end of the day it's still a rad and the bottle works as an expansion tank. The bleed screw is the black Philips head plastic plug.

OK cool, was hoping it was that plug lol

Joe sorry to hear you having problems with it.Really hope it hasnt cooked the head as it was skiimed/rebuilt couple of years ago as I mentioned when you picked it up.
The radiator fitted is an E36 M52 aircon rad which is more than up for the job.
I never used the original M20 bleedscrew when I did the engine swap,the one on the rad did the job fine.
I can only really suggest what other have already said about get the front passenger side of the car higher than the rest of the car,heater dial turned up to hottest temp and try again.

Fingers crossed for a good result!

Yeah that bleed screw on the stat was a pig! Didnt look like it had been moved for a while! Good ol mole grips lol

I have acquired some ramps so will get passenger side up in the air. Its my own stupid fault for not checking out the bleed process before replacing that split pipe!

If it has cooked the head, I won't be too upset because it means I'll have to fit an M52.... lol

Out of interest, how will i know if the head is goosed? Compression test?

Get in!

Just had another go, passenger side front up on a ramp, got it up to temp then bled off the rad bleed screw... More steam than a steamy thing and after restarting temp guage levelled out and hot air from blowers!

Just gonna top up with fluid and check bleed screw again, but signs are now good!

Cheers for the help chaps, much appreciated x

Sounds promising,keep us informed.