Bleeding advice (air bleeding procedure) '94 zxtd

[8304]

Hello again,

As in my previous post i mentioned that only the bottom 2/3rds of the rad are hot and the top 1/3rd is cold to the touch - i think that there cant be any water in the top of the rad there must be a big chunk of air sat in the top. When i was looking at the rad it didnt seem to me that there would be any way for that air to get out of the top of the radiator as it wil come up against the header tank on the far left of the radiator - (looking at front of car)

As i looked further thinking about the above, i noticed somthing that possibly could be a bleed point which i have never seen before and so never undone.

when bleeding in the past ive only ever bled in two places, the threaded cap arrangement at the top of the heater matrix hoses and the threaded cap situated just above the big black fuel filter housing. My question is:

IS THERE A THIRD BLEED POINT SITUATED ON THE TOP RIGHT HAND SIDE OF THE RADIATOR ITSELF?

This would explain why the top of my rad is cold!!

cheers in advance!!

Alastair

[mezuk04]

Im pretty sure there is a drain bit at the top right on a zx radiator

[8304]

thanks mezuk04

would this drain double as a bleeding point do you think?

I did undo it but there was no pressure in the system to push any air out becuase the rad cap was off at the time. Would there need to be pressure in the system to push the air out??

cheers

Alastair

[mezuk04]

Right im not a techy expert like most on here but me and wilkobob have done this a fair few times so im trying to remember now

I think all we do is undo the valve on the top right hand side and let it drain (not much comes out), we leave it open and then undo the left bottom tap (alot comes out ), i then decided to take off the filler cap and this chucked the water out from the bottom even more (im not techy sorry!)

then came the flushing a little through with a hose pipe, we then did up the top right valve and then the bottom right and then filled up using a header tank (as the engine is above radiator, you prob know this already)....we then filled up (with the little bleed caps already off and awaited for the coolant to come through this bleeds after all the air had come out and then quickly put the caps back on and filled the rest of the radiator.

Think thats about right, im sure someone else can clarify this but thats roughly it

[arry_b]

thanks mezuk04

would this drain double as a bleeding point do you think?

I did undo it but there was no pressure in the system to push any air out becuase the rad cap was off at the time. Would there need to be pressure in the system to push the air out??

cheers

Alastair

Although it looks the same as a drain point, it *is* a bleed point. Use a 2 litre pop bottle jammed in the header tank to raise the coolant level above the drain. Open the bleed until no air comes out. The haynes manual shows how it should be used, and it does work.

If you don't do that, you'll always have trapped air in the radiator - and a blown head gasket won't be far behind. Looking at your other posts about your cooling system, I think this is the root cause of your concerns. You have a huge volume of air which is expanding and forcing your coolant out.

Don't leave this too long ( I would do it before I drove the car again) especially as you're running extra boost.

'arry

[8304]

Thanks everybody for your responses.

It all makes more sense now as i have read elswhere about the use of a coke bottle or similar upside down in the header tank but never really understood the reason for doing this. I will do it this - evening.

earlier i did remove the plug from the top right hand hand of the radiator and added so water into the hole as the water was not up to the top of the radiator. I took it for a drive and the hoses seemed much softer, surpose that this is due to the smaller volume of air in the top of the radiator so it isnt expanding as much.

I will sort the problem imediatly but it is sort of comforting to know that with only 2/3rds cooling capacity on the radiator due to the air trapped in the top that the temperature gauge never goes above 85-90. The rest of the cooling system must be i reasonable condition goin by that

cheers

Alastair

[mezuk04]

I have a new radiator in my Xantia which i changed straight away when i bought it as there appeared to be a tiny leak, at the time of buying the temp gauge went up to around 85-90 like yourself, but with the new radiator it just sits below 70 with normal driving

[James.UK]

If the top of your rad has been full of air then your temp guage has probably been giving false readings due to the sender-sensor (situated in the radiator) being in air instead of hot water..

My ZX runs at about 80-85 in winter and 85-90 in summer. Stationary in summer it will get close to 100, in which case I open the windows and turn the heater on full for a couple of minutes, that normally brings the engine temp down again fairly quickly..

[8304]

Thanks for replys

drove to work this morning and the engine certainly ran cooler than it has been - it stuck around the 75 degrees mark and then climed after time to 80 degrees.

just hope i havnt provoked the h/g by driving around with it at 85-90 for about 14 months. It is fine at the moment though.....

One observation ive made is that the top rad hose is so much softer when up to temperature now. It used to be rock hard with the pressure but now is squidgy when hot - guess as air expands more than water when heated the extra volume of trapped air was putting the system under greater pressure.

Nice one!

alastair