Surging idle/Airlock issue?... SORTED!

Post by **NafemanNathan** » Mon Mar 11, 2013 12:18 am

Could a surging idle (revving between 1000 & 1900rpm) that begins 3-5 minutes after start-up from cold be caused by an airlock in the coolant system?

On the 3rd B20a7 by the way.

Post by **NafemanNathan** » Mon Mar 11, 2013 12:32 am

Yeah I've had the fan kick in twice with the rad cap off (Recon it took about 45 minutes to an hour), but when I did refill the new radiator nothing would come out the bleed valve of its own accord. I had to squeeze the lower rad pipe and even then it would only really blow air out. I'm going to try making a header tank to properly raise the level above the bleed valve as I think I need a bit more pressure to circulate the coolant.

andypont · Post by **andypont** » Mon Mar 11, 2013 7:57 am

I dont want to state the obvious, but did you have your heater slide right up to hot?
When I fitted my new rad i was getting air and then water out of the bleed straight away.

BMCC · Post by **BMCC** » Mon Mar 11, 2013 8:18 am

How did you fill the system? From memory you want to fill the system with the bleed bolt open so that as you pour the coolant in you push the air out. Once the coolant runs out with no bubbles etc then close the bleed bolt and fill rad to top with some in the expansion tank. Run the car with the heater a max hot with the cap off for a while (never bothered getting the fans to come on) then leave it to cool and top up the radiator & expansion tank. start the car and let it get hot and check for leaks etc and good idle. Top up if required.

Post by **indigolemon** » Mon Mar 11, 2013 9:47 am

^^ This, needs to be filled with that valve wide open and the heater set to hot.

Post by **vanzep** » Mon Mar 11, 2013 10:14 am

I had a nightmare time bleeding my 4th gen a few months ago - eventually fixed it by cleaning and loosening bleed bolt, filling rad and putting my mouth over the rad filler neck and blowing in to create pressure - also needed to fit new rad top hose and new rad. Twas a pain in the arse getting it to bleed - still dont know what the issue was but probably a blockage in cooolant system somewhere

Hope u get it fixed.

Post by **NafemanNathan** » Mon Mar 11, 2013 12:34 pm

Yeah I read your bleeding issues thread last night Nick, and I'd done exactly how Lemon and BMCC said in that and this thread. Bleed nipple open and heater set to max. I can even remove the bleed nipple completely and nothing will come out. If I squueze the lower rad hose though air does come out. I'm pretty sure the part of my drive where I was doing it is level, but I'm going to go out in a sec and move it up the drive to elevate the radiator for sure. Shouldn't really as I've got a stinking cold and cough, I'm off work ill and it's frikin freezing and windy out, but priorities ay?... MOT's at 4

Post by **NafemanNathan** » Mon Mar 11, 2013 1:23 pm

Ok, I'm pretty confident I've got all the air out the system, but it's still surging after about 5 minutes idling from cold

Just sprayed a load of carb cleaner around the inlet manifold to check for leaks too, but made no difference (I would have thought an air leak would have made itself known from the word go anyway

).

Any other ideas?

Going to let it cool (whilst I go and get it some petrol) then have another look. Also if I disconnect the plug from the IACV it stop surging and just idles fast and rough like a V8. (This is why I thought it was the IACV all along.)

Post by **NafemanNathan** » Mon Mar 11, 2013 3:51 pm

Well I made a nifty header tank up and stuck it in the neck of the rad. There's definitely no air in the system now. Still hunting though after 3-5 minutes.

Do you think it could be fuel related? She could be fine on cold start because she's running richer, but then once warm maybe there's not enough fuel getting through

...

Would that causing surging though, or would it just want to die?...

Post by **4thgenphil** » Mon Mar 11, 2013 3:52 pm

lambda sensor?