problem filling with coolant please help

[Keg_gt]

its getting hot and the pipes are certanly not full. dont go hard. and the pipe from the bottom of the rad to the thermostat stays cool

[Jesus325iTouring]

Correct me if i'm wrong but isn't the bottom rad hose supposed to cold where the water has past through the rad and been cooled

[Brianmoooore]

How do you know the pipes aren't full? What does the temperature gauge read?
If the pipes aren't getting hard, check the coolant pressure cap. O rings intact?

[murran]

drive over speed hump to bleed the system?? what ever next???

from disturbing the system as much as you have..... simply undo the upper hose from the heater matrix where it goes thru the baulkhead.... bleed it from there while topping it up. that done...... start it up.... do the 8mm screw thing on the thermostat housing/while topping it up.... you have water/coolant there.... then check the heater matrix pipe has you had off before again, while running this time..... both heater pipes going thru the baulkhead hot?? they should be....
keep an eye on the hoses going to the radiator, top hose should be hot bottom coldish till the thermostat opens then the bottom hose gets warm/hottish quickly. the guage shouldnt go over half way no matter what you do till the thermostat opens (bottom hose hot). by then you should noticably be able to hear the viscous fan doing its stuff when you rev it up........

[Keg_gt]

ok well been out topped it up a little and took it for a little spin to warm it up the temp gauge said it was getting a little hot so pulled over. and opened the bleed valve a little air came out then fluid. may have problem with the gauge though see link http://www.e30zone.net/modules.php?name ... 18#1192418

[Brianmoooore]

Bear in mind that the scale on the temperature gauge of an E30 is far from linear. The whole centre section is greatly expanded, and only covers a few degrees.

[Morat]

drive over speed hump to bleed the system?? what ever next???

It worked for me, got the last few bubbles out.

[spook]

I'm doing this right now, 3 key points:

1/ You have to get a minimum of 10 litres of coolant into the M20 system before starting the engine.

2/ fill the system in two separate places: header tank(fills the block and head) and bottom hose(radiator)

3/ take your time when filling, pouring coolant at the rate of 1 litre per minute avoids airlocks.

Slow and boring, but the job gets done properley and no worries about overheating and cracked heads.

Top up the sysstem with the last litre when system is leak tight at thermostat temperature

How can you fill a rad by pouring water thru the bottom hose? filling up thru the header tank must do the job,
iv'e just renewed all my rad hoses and refilled with new coolant, iv'e yet to run the car to check for leaks, again a 325i

[mark_i]

in the past I had problems filling the radiator because when closed, the thermostat prevented coolant returning to the block and airlocks in the rad were common when pouring in just from the header tank or the top hose.

If you remove the top and bottom hoses from the thermostat housing, I found it easier to fill the radiator from the bottom hose as the coolant displaces air as it rises from the bottom. That gets you 70% full and the remainder can be added to the rad from the top hose with the bottom hose connected and bleed valve open.

Also, the only way to fully drain all 10.5 litres from an M20 is to remove the drain plug under the exhaust manifold.

[Brianmoooore]

in the past I had problems filling the radiator because when closed, the thermostat prevented coolant returning to the block and airlocks in the rad were common when pouring in just from the header tank or the top hose.

Header tank fills the block, which then overflows to fill the radiator through the bottom hose. The air in the radiator escapes through the radiator vent, or via the air bleed at the top to the header tank.
A bit of care is required when refilling an E30 cooling system, but, as long as the car is not facing downhill, there shouldn't be any problems.

[spook]

Brian,so you can refill just by using the header tank, when the header tank is full, i need to turn the heater on, restart the engine, leave the header tank cap off , undo the bleed screw on the thermostat housing to remove any air locks.
Am i right in doing things this way

[Brianmoooore]

If the ignition is off, it doesn't matter where the heater control is, but it should be set to hot before you start the engine, and the fan turned on, so that you can check that the heater begins to deliver warm air, shortly after starting the engine.
Open whatever vents are on your particular engine, and fill slowly through the header tank. Close the vents when water without bubbles comes out. As long as the car is not nose down, this is all you should have to do.
If the heater begins to deliver heat after a minute, then all is well.
Make sure the coolant level is at least up to where it should be, and check again after a day or so.

[spook]

Thanks again Brian.
And thanks to your previous good advice i got my steering [guibo] back in without any problems, even though it took me most of Friday evening to get the old bush out of the coupling.

[Keg_gt]

ok slight amount of progress removed the small hose form the top of the rad back to the expansion tank and found this to be blocked. removed the crap from this seems to of improved slightly still go this horrible lumpy idle

[clipper]

Could the lumpy idle be anything to do with the ECU needing to reset its self, you said it was a major service, did you disconnect the battery ?

I've just got the engine on mine running after a while with the battery diconnected and the idle was terrible. Its been said on here before that the ECU may need to relearn its settings and sure enough after a short trip up and down the cul de sac where I live, getting up to about 4.5k revs in 2nd the idle has sorted itself out.

But just so you don't feel alone I can't get any more than 6.5 litres of coolant in mine either..... hot air from the heater, no air at the bleed valve, pulled hose off top matrix stub etc, etc.... temp gauge still heading for the red..... Its not easy !

[zimmerbimmer1]

The way our techs fill the coolant is this on M20 and M30 engines.

Remove rad cap, remove bleed screw make sure heater is put to hot

Fill coolant up through expansion tank until it pours out of the bleed screw with no air.

Tighten bleed screw and top up coolant til it reaches fill level put rad cap back on.

Start car up, whilst car warms up keep cracking open the bleed screw to get rid of any air in system

Check temp guage is at normal running temp and heater is hot.

Job Done

I recently did the thermostat housing on my 535i which holds approx 12.50 litres in total and it only took 6 litres to get it to the fill level as there was loads in the engine and heater still.

I also had a blocked vent pipe which caused the car to run hot and nearly cook the engine I replaced this and the coolant temp went straight to normal.

[clipper]

I'm not actually worried about the quantity of coolant that went in TBH. I did drain the water jacket but I know the matrix would have had some water in it.
Anyway, I'm pretty sure my thermostat is shot so I'm waiting for a new one to arrive before I continue. But I think I'll be having a close look at my vent pipe too. Thanks for that !

[Keg_gt]

yeah disconected the battery only happens once the car has warmed up. new rotar arm and dizzy cap added too

[Keg_gt]

ok lumpy idle fixed swapped back to my original maf and it sorted that problem still gets hot but tomorrow im going to drain the system jack the fornt of the car right up and refil the system now i have unblocked the vent pipe hopefully will be ok

[Keg_gt]

no its not ok
but now im not sure weather its getting hot or the gauge is lying
http://www.e30zone.net/modules.php?name ... c&t=112514
there is a link to the gauge problem or temperature grr this has gone on far to long now

[Keg_gt]

is it possible my si batteries are failing as i have noticed the red light only seems ot work intermitantly

[clipper]

I'm going to resurect / hijack this thread as the last thing we need on the tech forum is another thread about an overheating m20 !

This is just a final consultation to confirm my worst fears !

Full story below:

325i (pre) always had run at exactly half way point on temp gauge.
Car stolen and recovered with pipe to bottom matrix stub burst, blade missing off fan and mayo in the oil and coolant tank.
Head gasket replaced, head skimmed/tested, water pump replaced, coolant pipes replaced, thermostat replaced, viscous and fan replaced (2nd hand but from a m20b20 with no history of overheating, new fan is 11 blade, old was nine), all parts of cooling circuit flushed out.

Cooling system has been filled fairly succesfully following all the advice on this thread (except I've got no speed humps near my house to drive over ) and all seems good, hot air from heater, no air at bleed valve, bottom pipe getting hot, viscous fan unstoppable with newspaper, the system pressurises ok, the cap is fairly and is letting out excess coolant as the motor warms up but maintaining the system pressurised.

When the car is started it warms up quickly and gets to just over half way on the gauge before the thermostat opens at which point the temp gauge rises slower but continues to the third intermediate line, once its past this line I turn it off as I'm not prepared to let it get any closer to the red for obvious reasons.

So, is there anything esle wrong which I haven't thought about ? Something which could have happened to it while it was stolen maybe ?

Or is it time to admit that my head gasket replacement has failed miserably as I suspect

Or should I just get out there and drive it and stop worrying ?

[Brianmoooore]

Doesn't sound like head gasket failure - water doesn't disappear or get blown out the overflow.
Are you sure the radiator is cleaned out properly?

[clipper]

When I flushed the radiator the flow of water from top to bottom and bottom to top (I made sure I flushed it both ways) was very free and with a fast flow of water from a shower hose, a small amount of gunge came out but very little. The radiator is also almost brand new as it was replaced just before the car was stolen so its not as if there would have been much crap already in there.

Is there a way to be sure that the radiator is clean enough ?

Just in case this helps:

I went and had another look at it after typing the message above and decided to drop the front of the car off the axle stands and drive it around the car park a few times. After doing this the water level had dropped by enough to allow me to add about between half and one litre of water. So I checked for air at the bleed valve again and let the moptor warm up again, but it still went heading for the red.

Tonight I've left the pressure cap off as someone on here suggested to see if the water level drops........

[Brianmoooore]

Doesn't matter if the rad was brand new or twenty years old - if it's been filled with gunge, then it'll take some cleaning out.
Check that the small rubber pipe from the top of the rad to the coolant bottle is clear, including the stub pipes at each end.
With the pressure cap off, it will blow out the coolant.

[clipper]

Already checked the small link pipe and is all ok.

Looks like I'll be removing the rad to try to clean it out again....

[clipper]

Fixed.

Like the bad mechanic I am I have done two things at once and now don't know which was the fix, but anyway for the sake of closure:

Left the car sitting overnight with the pressure cap off, today the coolant level had dropped by about 2 cm. Possible air lock sorted itself out on its own ? Or possibly just evaporated... don't know. Topped up coolant level anyway.

Before firing it up I took out the clocks to check the nuts on the back, just in case the gauge was reading wrong. The nuts weren't loose but I loosened them and retightened just the same.

Now the car sits just under the half way mark on temp gauge and stays there. Yesterday the gauge was reading over half way before the thermostat opened so I suspect the gauge was misreading but I suppose I'll never know !

Anyhow, thanks to all for suggestions and advice, as always especially BrianMooore......

[Brianmoooore]

For the coolant level to drop, air has to come out, and the route it will have taken is via the small pipe I mentioned in my last post, so I still think this pipe may have been partly blocked somewhere, possibly inside the radiator.

[clipper]

For the coolant level to drop, air has to come out, and the route it will have taken is via the small pipe I mentioned in my last post, so I still think this pipe may have been partly blocked somewhere, possibly inside the radiator.

The thing is I had previously run the engine with the pressure cap off and coolant was clearly visible returning to the tank via the small tube so it can't have been very blocked... also it doesn't explain why the point at which the thermostat opens relative to the needle of the temp gauge has suddenly changed.

[Brianmoooore]

The change in the needle's position sounds about right for a 'repaired' connection at the back of the gauge.