Hello,
I have a very perplexing problem that neither I nor my mate who owns a garage can figure out. I recently put a new radiator in my 95 Jap Scooby due to a leak. It appears as though I have trapped air, let me first explain what I've done so far.....I've searched the posts and have tried letting it run with the cap off for 30+ minutes, squeezing the bottom hose till I couldn't move my hand anymore, and even lifted the front of the car to 30 degrees and tried everything previously listed that way too (yes, I had the heater on full the whole time). All to no avail, I took off the radiator tonight to check for blockage by both blowing through it and using a hose at full pressure-both good to go. I changed out the thermostat and seal with new parts, no luck. The symptoms are as follows-- The car heats up fine (20C) the air is very warm out of the heater, the water stabilizes in the tank, I put the cap on, take it for a test ride, soon after I get on the throttle, the temp spikes and the heater air goes cold. It stays this way for a minute or two then drops back down and the air gets warm again. The radiator is cool to the touch and the bottom hose is barely warm while the top one is very hot. Occassionally the "Check Engine" light comes on but goes out as soon as I hit the throttle. I of course checked the oil/fluids and there is no water/oil contamination nor any tale tell white smoke from the exhaust. I have a coolant system pressurization tool and the system holds pressure. There are no leaks to be seen either. The car runs fine and there is no lack of power. Everything is pointing at trapped air, how the heck do I get it out? Or is there something we're both missing? Water pump? We're both scratching our heads and could use your help, I need to get an MOT but need to sort this out first. Hope to hear from you, Lee

 

had my radiator changed at api,they had trouble with trapped air, they used some sort of pump to push the air out,think the air lock was in the heater matrix cheers mark

 

i don't know if this will help or even if its the right way to do it but it worked on mine.. I filled the system up from the top of the radiator.. As in i removed the top hose and poured the antifreeze/water in the top of the radiator (i removed the filler caps) and once the water started pouring out of the top hose i reconnected it. I also then topped it up from the filler caps. On my radiator theres also a little bleed valve on the bottom left on the cam side (if your looking from the front of the car). If you have one try bleeding it throught there first (top it up at the same time though).
Hope this helps.. worth a try anyway.

 

drain the system completely by removing the thermostat.

Refit the thermostat then use the top hose (with one end removed from the rad) to fill the block, pour slowly.. once its fill connect one end to the rad and leave the block end disconnected and fill the rad slowly until its full.. Completely re-attach the top hose and fill the header tank.

 

Id say drain the system and refill it. Hovever a very old engineer who trained me told me a way to get out airlocks. Add some cooking oil to the water it breaks down the surface tension and therefore the large bubble collapses into a lot of small ones which are more easily absorbed. He knew what he was talking about but I never tried it. He also told me how to temp fix a radiator or head gasket with an egg but thats a different story. "during the war" >LOL

 

best way I have found of doing it is as Davey says, less likely to get any air in that way. Also what I did was put the cap on to let the system pressurize, with heater on hot and blowing then every few mins remove it (being careful) and topping up if neccessary.

Also its a good idea to flush the rad before fitting it.