how to clear an air lock in the rad

[rasco]

Before I get started, I've had a search of this forum and others, and have read of many different ways to bleed the coolant system. What I'm trying to find out, however, is how I specifically clear an air lock in the rad. My fans don't come on at the right temp (despite new thermoswitcH) and I've read another thread on here where people found it was due to an airlock in the rad.

They seemed to approach the issue in a couple of different ways. One guy "filled rad from top hose", and another did the following:

"I put the car up on a slope so the front right (rght hand drive offside) was definately the highest point (and at a nice slopey angle, to encourage any bubbles in the rad to move), and bled the system including squeezing the pipes, and revving the car to 3000rpm, until the CTS on VAGCOM reported about 93 DegC (and the coolant was starting to steam). I then put the cap back on and went for a high rpm thrash, including putting the heater on max temp and fan".

Which method should I take? I'm temped to take the following approach:

- start with an already reasonably warm car
- jack up the car on the drivers side front, so that the reservoir is elevated
- take the reservoir cap off
- start engine and let it get up to temp
- squeeze pipes - at the moment I'm not sure which ones I'm meant to squeeze...
- increase revs for a couple of minutes (2000rpm enough?)
- top up as necessary, squeeze pipes again
- turn off engine
- do I:
1 let the car cool before fitting res cap back on, or do I
2 fit the cap back on, take car for a spirited drive, park it, engine off, remove cap and leave to cool, or
3 simply leave to cool before refitting cap, then take for a drive another day.

any advice much appreciated! I've only bled a coolant system once before (not on the leon) and just ran the engine with the rad cap off, and topped up coolant at the rad (bit messy but it worked....)

 

[towcester vag]

leons dont suffer from airlocks
it must be something else causing this

 

[andycupra]

its a self bleeding system. just fill it up and run it.
although make sure you fill it up via the expansion tank and have some more handy, start car with cap still off and top up as necessary. once its not taking more, then take it for a drive and up to temperature and top as as/if necessary.

 

[rasco]

but people have had this problem before, and have bled the system by squeezing pipes and/or filling at the rad and report it fixes their issue. So surely although it's meant to be self-bleeding, air locks can still happen?

I'm stumped with ideas on what else could be causing my fans not to come on until the CTS reads 105oC, with the thermoswitch in the rad being new (and shorting the pins on the thermoswitch plug spins up the fans)...... I'm certainly open to ideas!!

 

[JDUB 20V]

but people have had this problem before, and have bled the system by squeezing pipes and/or filling at the rad and report it fixes their issue. So surely although it's meant to be self-bleeding, air locks can still happen?

I'm stumped with ideas on what else could be causing my fans not to come on until the CTS reads 105oC, with the thermoswitch in the rad being new (and shorting the pins on the thermoswitch plug spins up the fans)...... I'm certainly open to ideas!!

Is your thermoswitch genuine?

 

[BoostHard]

Im sure I read on vortex there is a bleed hole in one of the metal heater matrix pipes,
You can slip the rubber pipe back to expose the hole, Once coolant comes out the hole you push the pipe back on.

That's what I read in the guide anyway.

 

[traumapat]

Does the dash gauge dropped down from 90 when driving?.... faulty coolant thermostat?

Ive never had an airlock problem in 8 years of ownership.

 

[rasco]

no, I don't think my thermoswitch is genuine, but the previous one used to start the fans at the same sort of temperature (106oC). Mech topped up the coolant when fitting new switch, so I do believe an air-lock is unlikely, but I'm stumped. It had a new thermostat and water pump in february, and new fans and thermoswitch last week. Mechanic tested the fans came on in both low and high speed when bridging the pins of the thermoswitch, and two other people have reported similar symptoms, replacing pretty much all parts (including the fan control module) and found their issues were fixed by bleeding the coolant system. their posts are on the last page of this thread:

http://www.seatcupra.net/forums/showthread.php?t=137571&page=18&highlight=bleed+coolant

I'd have reason to doubt the thermoswitch if it performed any differently to the last one, but it doesn't.

 

[rasco]

thing is, I'd never have known there was a problem if I didn't have a liquid gauge fitted, as the coolant temp needle never leaves 90oC, even when the fans do eventually kick in. Cooling system works perfectly in every other way, just that the fans come on late.

 

[traumapat]

Personally if the dash gauge works perfectly and doesnt go above 90 I wouldnt be fixing anything. It isnt accurate... will only rise when a certain parameter has been breached but if its not getting hot enough to worry the ecu it wont move.

Just check the coolant is circulating and fans eventually come on?

 

[rasco]

yep, coolant circulates, and fans do eventually come on at 105oC. Is 105oC OK then?

 

[traumapat]

yep, coolant circulates, and fans do eventually come on at 105oC. Is 105oC OK then?

If dash is at 90 id not be worried.. but then I dont have a liquid gauge.

 

[rasco]

ok bit of an update, and a new question.

I've been sat in traffic a couple of times and have had the cooling fans come on at various temperatures now: 95, 96, 98, 99, 101. So it appeared to be working better.

Today though, I had the fans kick in at 98 while stuck in traffic (car horizontal), then was stuck in traffic on a motorway on-ramp. Car was pointing downwards at this point. I sat waiting for the fans to kick in, but they didn't. liquid gauge got to 107 and the temp needle on the dash started to rise, so I gave up waiting and switched the AC on to force the fans on. Later, on the motorway, I was stuck in traffic again and the fans kicked in at 99 degrees (car horizontal again).

When I tested my car on the drive, my car was pointing up slightly, and the fans didn't kick in till 105.

So my question is; when the car is pointing up or down a bit, does this affect the coolant flow significantly? Should I be concerned?

Cheers all