Bleeding the coolant on a 325

Sat Sep 17, 2011 10:45 am

I'm having problems bleeding the coolant on my 325. Ive had the heater matrix off and now its all back together the temperature gauge just goes into the red so im guessing theres an air lock in the system. I thought it was the thermostat so tried it without one but still no joy. when i undo the bleed screw on top of thermostat housing it just throws out coolant no air bubbles at all. When it gets hot and you feel the pipes theyre all hot apart from the bottom hose on the radiator!

Any ideas on this or tips for bleeding these things up?

Cheers max

Sat Sep 17, 2011 2:23 pm

Fill the coolant bottle well above the correct level, leave the cap off and pull the overflow hose back in through its hole in the inner wing.
Remove the top heater hose at the bulkhead, put the free end of the overflow pipe in your mouth, your hand flat over the top of the coolant bottle, and blow gently into the pipe. as coolant starts to flow from both the heater hose and the stub pipe, push the pipe back on the stub.
DO NOT run the engine with the airlock - it's a very efficient way of cracking the head!

Sat Sep 17, 2011 3:13 pm

You HAVE had the heater on hot I'm guessing?

Silly question I know, but..........

Sat Sep 17, 2011 8:30 pm

Thanks for reply fellas. Yep the heater is on hot. Thanks brian i'll try that tomoro and seehow it goes.

Sun Sep 18, 2011 1:44 pm

Still no joy. the coolant was already flowing out of both the heater matrix stub end and the hose. Evey hose is hot apart from the bottom hose coming from the rad up too the thermostat! Why is this. Any other suggestions?

cheers max

Sun Sep 18, 2011 1:48 pm

Can i just ask why you hd the matrix off? did you replace it?

Sun Sep 18, 2011 2:00 pm

Rain water was leaking in through the seal between the bulk head and heater matrix housing and it needed some welding on the bulk head.

Sun Sep 18, 2011 2:40 pm

Hold a finger over the heater hose end and blow harder! Get coolant flowing as fast as you can from the heater stub.

Wed Sep 21, 2011 7:49 pm

Still cant get it to bleed up. ive tried all the above. i got the coolant flowing really fast out of the stub connected them bk together and topped it up keeping the header tank full. Tried it with and without the thermostat in. tried it with a hose pipe in the heater matrix hose untill water was pouring out of the stub then reconnected to make sure there was no blockages. Stripped it down to check the water pump and that was fine. Temp gauge just keeps going round to the red and the bottom hose on the rad just stays cold. Heater is still blowing warm.

No idea what to try next. does it mean the airlock is in the rad if the bottom hose is cold?

Wed Sep 21, 2011 7:55 pm

Is the hose from the top of the rad. into the coolant bottle clear? You should be able to see the coolant flowing from it into the bottle at anything above about 2000 RPM.
Apart from that, there's nothing I can think of that you haven't tried.
Are you certain it is overheating, and not a gauge fault?
Does the heater blow hot?

Wed Sep 21, 2011 8:29 pm

the hose is clear i can see it pumping water back into the bottle when you rev it.
I'm quite sure its not a faulty gauge. And it surely has to still have an air lock in it for the bottom hose to be cold on the rad up to the thermostat. The heater is blowing hot ish, i dont remember it being much hotter before.

Thu Sep 22, 2011 10:27 am

Are you sure you have the right thermostat in it? It needs the second seal on the bottom of it to shut off the bypass pipe when hot.
Are you sure the bleed valve on the 'stat housing is clear?

Thu Sep 22, 2011 6:01 pm

Yep im sure its the right thermostat cos its the same one i had in before i just took it out to test it in some hot water and you could see it opening so theres nothing wrong with that. The thermostat bleed valve is definately clear because coolant pours out of it when i unscrew it.

Im staring to wonder if it is a faulty temp gauge like you say. Because ive had the dash and clocks out to get to the heater matrix. And now for some reason the rev counter doesnt work at all( wasnt brilliant before, just worked when it wanted too) but also the fuel gauge has gone funny too. The petrol light is on but the gauge is showing half a tank!

Also ive been told that the bottom hose shoudnt be as hot as the rest (not sure if this is true or not)

The temp gauge does go up as the car gets warmer and goes bk down when its left to cool but i have noticed sometimes its a bit erratic, it doesnt go up smoothly. Is there any chance it could be a faulty temp sensor maybe.

Not going to get chance to have a mess with it for a bit as its at my friends garage but i'll keep you up to date.

Thanks for all your help so far. Max

Thu Sep 22, 2011 11:32 pm

Loose nut on the back of the cluster, behind the temp gauge can make the needle twitch and read about 1/6 higher on the scale.
Non working rev. counter suggests that the rechargeable batteries on the SI board in the cluster may have died when they were disconnected from the main car battery. This can affect the temp. gauge as well.
Petrol gauge will read half when the tank is empty (light on) if the LH fuel level sensor is stuck on full, or if the tank has been changed for a 55 litre one.

Fri Sep 23, 2011 5:40 pm

e30max wrote:Rain water was leaking in through the seal between the bulk head and heater matrix housing and it needed some welding on the bulk head.

Thats not a seal, it's just a foam gasket, I wouldn't mind betting the grommet on your wiper spindle is perished, you would not beleive the amount of water the can pass through it, water will drip straight on to you heater box, fill it up then leak out the bottom, the foam gasket soaks up a fair amount to be fair so it could take a while to start leaking again.

Mon Sep 26, 2011 7:16 pm

Right just had another go with the car. I'm pretty sure its the temp gauge ive had it running for ages the heaters are blowing out hot air, bottom hose on the rad has now got hot. The gauge is now sitting between the 3/4 mark and the red section. still no rev counter, if the batteries have gone in the the back of the clocks could this be making the temp gauge be that far out?

Mon Sep 26, 2011 8:56 pm

fixed the rev counter, turned out it was just a fuse. temp gauge is still up near the red though!

Mon Sep 26, 2011 10:01 pm

Tried another temp sensor but it still reads just above 3/4 mark so its not that. Wonder if the viscous fan clutch has had it. should it be hard to stop when the engine is hot? Is there a better way to check it rather than the newspaper check?

Tue Sep 27, 2011 9:16 am

You can easily hear when a viscous fan is locked if you rev. the engine. Never seen the point of, or used, the "newspaper test".
You are describing what is a fully working, perfectly normal engine in all aspects apart from where the gauge sits.
Does it sit still, once it's reached where it gets to? Does switching the heater to full hot, the fan to full, and opening all the vents have any effect on the reading?
This really needs an independent check on what temp. it's really running at. Even some bottom end test meters have temperature measuring functions these days.

Tue Sep 27, 2011 9:36 am

Another trick is to drill a small hole (2mm) in the stat outer ring, refitting the stat with the hole at the top. This makes bleeding a bit easier.

I always refill cooling systems through the top hose once it's been disconnected from the rad. Do it nice and slow as well.

Viscous couplings - if it looks old and grimy, it's on borrowed time so is best replaced. £35 from Andrew Page for a Borg Warner unit.

Tue Sep 27, 2011 9:44 am

im thinking if it takes a very loong time for the bottom hose to get hot, that it could be the water pump!

Tue Sep 27, 2011 10:38 am

Quaser wrote:im thinking if it takes a very loong time for the bottom hose to get hot, that it could be the water pump!

Proves you have an effective radiator.

Tue Sep 27, 2011 4:35 pm

Brianmoooore wrote:
Quaser wrote:im thinking if it takes a very loong time for the bottom hose to get hot, that it could be the water pump!
Proves you have an effective radiator.

Indeed. In the winter months, the bottom rad hose will still be cool, even after a long motorway run. My Compact's bottom hose will still be cool after 150 miles of the M1.

Mon Oct 03, 2011 9:59 pm

Hi mate id change the thermostat I had same problem,put it in water and it was opening and closeing but just for my own peice of mind I changed it for a new one and hey presto problem gone.

Fri Oct 07, 2011 9:04 pm

Think ive sorted it now. With me having the dash out there was wires everywhere so i didnt spot it but when removing the dash i took off a cluster of earth wires all on the same bolt connected to the bulk head and when i refitted it i never re attached them

when i did the petrol gauge started to work properly so i left the car running and the temp gauge never went over half way. Just took it out for a spin and everything seems fine so fingers crossed thats all it is.

Thanks for all your help fellas. Much appreciated.

Max