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Changed the timing belt, now I have air in the coolant

4K views 20 replies 10 participants last post by  OBDad 
#1 ·
I hate all things coolant related. I think I have PTSD from a 4.7L Grand Cherokee that blew the head gaskets and had coolant issues.

Anyway, I changed the timing belt this weekend on my 11 Outback, along with the water pump. I didn't take out the radiator, as it wasn't needed. Now, I have water running behind the dash.

I have an FSM and refilled the coolant system as specified (idle until the fan kicks on and off, race the engine repeatedly to 2000RPM, then to 3000 RPM, etc), and when I went to drive it to work this morning, it still has water rushing.

When I checked it after it cooled off from the FSM purge cycle, the coolant was still high in the radiator (to the neck) and I overfilled the reservoir tank so there should be plenty to pull from (I filled it halfway up, about 2" above the "full" line).

So, today on the way to work, I got a trickle when I stopped the first couple times (I only have 3 stops over 14 miles...), but not the last, and I attempted again to do a modified purge cycle by keeping it under 2000 RPM until it warmed, then rev over 3000 RPM from the stops.

Because this is my life, and nothing ever comes easy when it comes to easy car mechanics, I'm going to assume that the problem is still there this afternoon when I leave. WTH do I do to get the air out of the system?
 
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#2 ·
Try lifting the front: ramps, small hill, climp up on something, back up into the ditch (if not too steep). I was watching random repair videos a few weekends ago and one of them said Subarus can be a pain to burp.
A rad bucket might help too. Try squeezing the top rad hose to force some air out.
 
#3 ·
annoying indeed. job well done...then symptoms...grrrrr.. they're tricky sometimes.

was the water pump replaced just as part of a routine timing belt job or chasing an issue?

nose up and keep refilling usually works. usually takes 2 or 3 times at home, idling-cool down-check-repeat.
there's no magic trick, screw, hose, or process.

in general most well versed SUbaru people leave the water pump til the 2nd timing belt change and replace the idlers and tensioner instead, (or replace it all - including cam seals/reseal oil pump). tensioner/pulleys are far more prone to failure than the water pump, and typically cause valve damage when they fail. subaru water pumps only ever leak externally, cause no stranding or engine issues unless it's ignored or abused.
 
#4 ·
I had success following the FSM procedure when I drained out the coolant system for a block heater install and actually didn't have to do any further work.

That being said the FSM procedure is different than what I usually do. I like to run the engine (idle, in P, hood up) with the radiator cap off, and the front of the car slightly higher than the rear. Like mjohnson I like to squeeze the top hose to get more bubbles out. Once it starts bubbling over I turn the engine off and let it cool for a couple minutes. Then I refill, and run the engine until it bubbles over again. I repeat 3-4 times, then let it cool all the way. I then check the levels in the reservoir and radiator and top off.

I also run the heater on full blast, but that's likely not needed on a modern car. I just do it as a carryover from the older coolant system designs where switching the heat on would literally open a valve to let coolant circulate to the heater core, so skipping that step would leave bubbles in that part of the system.
 
#21 ·
I like to run the engine (idle, in P, hood up) with the radiator cap off
DO NOT OPEN THE RADIATOR CAP LEST YOU WILL ALLOW AIR INTO THE SYSTEM... hence restarting the cycling all over again.
WHAT ASOLUTE NONSENSE
Heh, heh... well one can't accuse you of being indirect in your assessments. I personally prefer to weigh my words a bit more since it tends to focus the discussion on collaborative feedback instead of proving "who is correct" and "who insulted who".

As you can tell from my self-quote above I do agree though - it works great to run the engine with the radiator cap off to do the initial bleeding of the system, and it's normally my preferred bleeding method. Just stop when the coolant starts bubbling over.

The reason why there is air in the system is because the air will NEVER have a chance to be released if the radiator cap stays on.
That I don't fully agree with. The reason is because as the engine cools off the valve in the radiator cap releases pressure into the reservoir. If air bubbles have found their way to the top of the radiator they will be flushed out when the pressure release opens. The reservoir is NOT air tight so the air will escape. So I wouldn't say it NEVER has a chance to escape, but it is usually slower and takes more heat/cool cycles to bleed than if you start with the cap off.

In fact, the Factory Service Manual (FSM) procedure does not involve running with the cap off, and that worked for me. I decided to follow the FSM when bleeding instead of doing what I normally do and run with the cap off.... And I never really had to do anything other than the FSM procedure.
 
#5 ·
Gary, I replaced it just because it was time (well, past time, it's got 140K miles...oops...), and the project was a bear enough that I didn't want to deal with it again in 40K miles because I didn't do the water pump. Besides, it was included in the kit.

OBDad, I'll be interested to see what it does this afternoon. Like you, I usually just burp it a couple times, but I don't have ramps and my driveway is mostly flat, so I was hoping not to have to do the whole rigamarole. I also run the heater on high, and drove with the heater on high (and fan on low) the whole way here.

Just went out to start up the car, and at least in park (and the cold temp light on), I didn't hear any water. I'll try again on my lunch break.
 
#7 ·
Yeah I've refilled my car a number of times. Idling with radiator cap off and heat on as stated above gets you most of the way. After that as you found out the bubbles will work their way out the overflow and it will suck itself full after a couple three four heat cycles and driving with with cap on.

140k on the EJ huh?! Brave man.

Fwiw my first water pump change at 100k was needed. The bearing had noticeable play and seepage was noticeable at weep hole. Second pump at 172k [72k on pump) was perfect though. Better safe than sorry.

Sent from my SM-G900R4 using Tapatalk
 
#8 ·
One of the pulleys had some play to it, but the belt still looked good (still had the timing marks on it!) and wasn't cracked or worn in any way. If I wasn't so paranoid, I'd have been interested to see how long it would have gone before blowing up. Given the way everything looked, I'd assume that one of the bearings would have given out before the belt did. All of the other pulleys were good, and the water pump showed no indication of needing replacement, but the job is such a PITA I figured I'd just replace it before it needed it.

And, the tensioner by the water pump was a bear to get on. Best sound ever? When you're trying to get it on, and it pulls the cam pulley and you can hear the thudthudthud of the valve knocking the top of the piston. On well, got it back together and it runs like a watch.
 
#10 ·
I have replaced mine recently, at 130K with the same results. Everything looked pristine.

The thud thud thud sound? Weren't you in middle stroke? I could turn my cam sprocket 360° (and back again, just out of curiosity and to check to make sure I had clearance to do what I was doing) without any contact.

Woops, I didn't burp mine, although it was a tad low 2 days afterwards and a little top off solved it and haven't been low since. I guess I overlooked the burping procedure.

Sent from my Nexus 6 using Tapatalk
 
#12 ·
It sounds to me as if you have not "cycled" the system enough times. It takes AT LEAST 10 heat/cool cycles to burp all the air out of the system. It may take over 2 MONTHS of daily driving before the antifreeze-level in the resivour becomes stable.

At the risk of repeating what you already know:

A freshly-filled system has MILLIONS of microscopic air bubbles throughout the system. Over time, these bubbles coalesce into trapped air which rises to the highest point of the system awaiting the next 'purge cycle' to expell.

*) Each heatup cycle pushes trapped air from the highest point of the system out into the atsmosphere. (thru the resivour tank)
*) Every cooldown cycle sucks fresh antifreeze from the resivour into the system.

DO NOT OPEN THE RADIATOR CAP LEST YOU WILL ALLOW AIR INTO THE SYSTEM... hence restarting the cycling all over again.
 
#18 · (Edited)
WHAT ASOLUTE NONSENSE

The reason why there is air in the system is because the air will NEVER have a chance to be released if the radiator cap stays on.

This is how you do it and it works for all vehicles; have been doing it this way for 40 + years.

fill up system start engine and run for up to 20 - 30 minutes with radiator cap off topping up when necessary. ie keep radiator full up to neck.

This is to allow air to be released as engine comes up to temperature with thermostat opening and coolant being circulated through out engine then radiator and air being released at its highest point at the open radiator cap.

It is a well know basic fact that air rises through water under motion.

Air WILL NOT be introduced into the water via radiator cap opening so long as water / coolant is kept topped up.

Once satisfied replace radiator cap. switch off engine, top up over flow reservoir to correct level . This allows engine to draw water back into radiator as it cools down as water volume contracts with cooling down.

Other nonsense like squeezing hoses / parking on slopes etc a waste of time !!!!!
 
#13 ·
It's nice having a civilized car that is designed correctly. With the grand, the highest point was the thermostat housing in top of the motor. There was an Allen bolt that you took off to fill from there to eliminate trapped air. Further, the heater core was designed in such a way as not not allow air to be purged unless you had the front drastically high off the ground, as the hoses that went to it entered the core in the middle of the right side. Who does that??

Long story short, the outback had resolved itself. Now to get over the paranoia that is involved with the burning-off- antifreeze smell for the next couple days and we'll be good.
 
#17 ·
Morning! So I'm sitting at 108K, I'm guessing it's "time" (ba-doom ching, wah wah) to change the timing belt? Was dreading the day I got here....to DIY or to take it to the mechanic....is it a difficult or time-consuming job? I know with my Volvo you basically had to tear down the upper half of the engine. Thanks.
 
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