4A-GE AW11 Cooling question - Backpressure?

[senn]

Been playing with the car as it started running warm and trying to cook itself. Have bled the system, flushed the radiator, replaced the thermostat, cooling system (radiator) cap bled it up etc.

However my question is this. When i'm refilling the car, with the cap off, if i rev the engine, should the coolant be trying to spray out the fill point? Or should it be dropping? Should i be able to see the water flowing past the fill point before the car is hot enough to open the thermostat or not? I'm asking because i suspect perhaps my water pump is dead/dying, and i had thought that the reason it was getting backpressure was just air locks as i bled the system, but i'm not so sure now. Someone said the coolant expanding rapidly from revving the engine might be enough to push it out (didn't think it would expand that much?!)

Any advice would be greatly appreciated, as this is the first cooling issue with the aw11 i've had. Every other time i've had to do a coolant refill + air bleed it's been fine, but this time something else is causing me issues.

I have read the 4A's cooling system is the opposite of a normal cars regarding how the thermostat works, but can't work out how i can tell if the pump is knackered without having to rip half the engine bay apart. Knowing when i can check for flow would be helpful.

Thanks in advance.

[trdee]

if the waterpump is dying you should see water coming out of the weep hole

[TRD-12A]

not necessarily unless the fins have disintigrated and are no longer existent, the only way to find out is to pull it off. Can you see the water flowing in the radiator at all or is it boiling pretty much instantaniously??

[senn]

doesn't seem to be boiling, unless thats what is pushing the coolant out the fill point so quick? It's not bubbling excessivly at the fill point, so does that mean it isn't boiling? I had originally thought that the water pump was ok, and the water was being pushed out due to airlock/blockage somewhere in the cooling system. But i'm not so sure since someone mentioned the expansion thing, tbh i hadn't thought of it expanding that quick..

On that "weep" hole, i honestly didn't know about it (read some stuff last night about what it's for) so i didn't look for it, will have a check next time i'm at home..

"just pulling it off" isn't a phrase i'd use in this size engine bay, it's not like doing it on a FR layout car hehehe. I'd say it'd be a couple hours work to get at it, doing it in the car, without removing the engine. That's why i wanted to try work out if it's working or not before i rip it to bits. But, i'll have to do it some time i suppose

[feral4mr2]

bit hard to see in this diagram, but you can see the water pump directly feeds the section the radiator cap is on. so while filling your system if you rev the engine you will have coolant spill out the hole. i've done it many times getting impatient when doing a coolant change.


do you have the rear of the car up on ramps while your re-filling the system?


after i have initialy filled the system (rear of car up on ramps) i bleed the radiator, heater and thermastat. then i start the car and let it 'burp' itself while topping the coolant level as it drops from the 'fill' point. once the car has reached operating temp while your doing this you should be able to see the coolant passing the fill point when the thermastat opens.

[Twisty92]

Try putting a Co2 leak detector on there, since you've replaced everything bar the water pump pretty much

and if their is bubbles coming up( through the radiator top) when the engine is running at about 2000 rpm, could mean cracked head.

is the thermostat the right degree when it starts to open?

is the radiator cap keeping pressure in the system?

Hope this helps
Twisty

[senn]

Rad cap is TGP new, thermostat is TGP new 82c unit, haven't tested it. Hmm makes me feel a bit better that it should be being pushed out the fill point...if it is "just" an air lock somewhere i might have to give it a bleed + drive, and bring it back and put it on the ramps overnight or something, see if whatever it is makes it's way out of the system.

I'll run it up to temp and double check to see if it is flowing when the thermostat opens. If it isn't or looks like it's sluggish, i'll throw a new wp in it.

Thanks again for your input guys, i feel like a bit of a dumbass not being able to get this working properly lol. Fingers crossed i can get it working for the weekend of the 13th-14th

[Twisty92]

No worries
i bet ya find it and think why didn't i think of that first haha

[allencr]

If it isn't or looks like it's sluggish, i'll throw a new wp in it.

I'd look at the radiator being restricted or just a natural effect from the loooong water path.
The water-pump is the absolute Very Last Thing to suspect!!