Difficulty bleeding coolant, possibly because it's too cold outside

[slacktide_bitog]

98 Forester

I just replaced the water pump and thermostat and thought I got the air out, but coolant is still pouring out of the overflow bottle, and the radiator cap is cold. It's an Aisin water pump and a Facet thermostat, no Chinese or Motorad garbage. The radiator cap is a Sankei cap I got a few years ago.

When I did the burping, the lower hose got hot, and the fans finally tuned on after almost an hour. I used the Lisle funnel and saw the bubbles, and then eventually the bubbles stopped.

Unfortunately, I couldn't run the heat the whole time because then it would never get hot enough to keep the fans on.

 

[Chris142]

What kind of car?

 

[The Critic]

Did you not read the service instructions before doing this job?

If you don't have a vacuum filler, there is a specific procedure for bleeding these.

 

[ripcord]

My dad used to hold the thermostat open with an aspirin tablet when replacing them. That way the air could escape during the initial fill before it dissolved.

 

[trd1zz]

Use a stick / shower rod / whatever on the gas to hold the revs up a bit

 

[Passport1]

Elevate the nose of the car a bit on ramps. Leave the radiator cap off if it doesn't vomit coolant.

 

[Nukeman7]

When I did the burping, the lower hose got hot, and the fans finally tuned on after almost an hour. I used the Lisle funnel and saw the bubbles, and then eventually the bubbles stopped.

Unfortunately, I couldn't run the heat the whole time because then it would never get hot enough to keep the fans on.

Depending on the design, if you don't run the heater temperature setting on high during the purge process, air will remain trapped inside the heater core. It really doesn't matter if the fans run or not as long as the thermostat fully opens when the engine attains operating temperature.

Assuming this is the Subaru Legacy on which you stripped the water pump bolt changing, check to verify it is not leaking.

I don't know if this video might help, but I'm posting it just in case.

 

[Hirev]

Some vehicles have very stubborn coolant systems. The method I use these days is raising the front end high as I can get it when filling coolant. It works because air travels to the highest point in the system,

 

[mk378]

Set the heater temperature dial on high so coolant flows through the core, but leave the interior fan off.

If you're getting heat from the heater the system is reasonably full. Take a short drive then park and allow to get fully cold then open the radiator and top it off. As noted, park facing uphill or at least on level ground, not nose down.

 

[The_Jeff]

When the car's halfway warmed up, point it up the steepest hill you can then punch the gas in low gear.

 

[Dborch41]

I am a BIG proponent of vacuum-filling cooling systems. I got a cheap kit from you-know-where, they're almost all the identical tool with countless different brand names. I've only used it a couple of times but the process works so well it was well worth it.

The only disadvantage is that they require a rather healthy air compressor to run the venturi "pump". The fitting on mine broke almost immediately (did I mention it was cheap?), so I adapted it to use my A/C vacuum pump instead. Sometimes those can be rented.

I'll never burp-fill-wait-burp-fill-wait again.

 

[The Critic]

I am a BIG proponent of vacuum-filling cooling systems. I got a cheap kit from you-know-where, they're almost all the identical tool with countless different brand names. I've only used it a couple of times but the process works so well it was well worth it.

The only disadvantage is that they require a rather healthy air compressor to run the venturi "pump". The fitting on mine broke almost immediately (did I mention it was cheap?), so I adapted it to use my A/C vacuum pump instead. Sometimes those can be rented.

I'll never burp-fill-wait-burp-fill-wait again.

Vacuum fill only works when the system is mostly empty. If your system is still half-full, it may not always work.

Also, on a lot of complex cooling systems, vacuum fill only gets you the ability to bleed the system without overheating; you still have to bleed.

 

[Coolant Kid]

As a long time Suby enthusiast that has done a lot of work on these EJ25 engines, I would suggest changing the thermostat to either OEM or Tama as something you could try. But honestly, this sounds like a blown head gasket. These engines are extremely easy to bleed, it takes almost no effort at all to bleed them. Put the front end on an incline, fill the radiator, start the engine, fill it again, drive around for 5 minutes, let it cool, then refill the radiator and overflow and that's it. I've done it too many times to count on both DOHC like yours and the SOHC models. All the same. And yes, I've changed head gaskets on these engines too, so I'm familiar with these symptoms.

 

[Trav]

Pulling the hose off the TB when filling is a good way to do these, remove the hose and fill slowly, vacuum filling does a good job also.

 

[slacktide_bitog]

As a long time Suby enthusiast that has done a lot of work on these EJ25 engines, I would suggest changing the thermostat to either OEM or Tama as something you could try. But honestly, this sounds like a blown head gasket. These engines are extremely easy to bleed, it takes almost no effort at all to bleed them. Put the front end on an incline, fill the radiator, start the engine, fill it again, drive around for 5 minutes, let it cool, then refill the radiator and overflow and that's it. I've done it too many times to count on both DOHC like yours and the SOHC models. All the same. And yes, I've changed head gaskets on these engines too, so I'm familiar with these symptoms.

NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

Don't say that

I put in head gasket sealer a few years ago. I thought it would still be holding up

So far, the coolant isn't bubbling, and sometimes the temp gauge will go back down, then go up, then back down. I thought if it was the head gasket it would just stay hot. But the HG blew again, I still have the other half of the bottle, as the instructions only said to use half the bottle. I used Bars Leaks HG-1.

Couldn't the head gaskets have waited until after I got to install my bakes and axles to blow again?

I know the newer Subarus require the special procedure in the manual or a vacuum filler, but I didn't think the older ones would need it, though the 98 has that same procedure listed in the service manual. I used the Lisle coolant funnel.

Someone on YT got at least 8 years out of head gasket sealer
(the guy in the video used Blue Devil)

 

[slacktide_bitog]

So, I drove it again for about 10 miles (5 miles each way, including some heavy traffic on the way there)., but I only stopped to pick up an online order and I was only there a few minutes), and the car did not overheat

Before the water pump replacement, it would overheat after a mile or two.

The trip I took yesterday was 15 miles (30 miles round trip), and started overheating after 25 miles

 

[Coolant Kid]

On these EJ25 engines, head gasket replacement is practically routine maintenance. They all blow eventually. And once you replace them, they don't stay fixed forever, regardless of what others say. It's just a matter of time, but the same symptoms will return at some point. On a poorly done job, could be a year or less. On a well done job, maybe 5 to 10 years depending on how much it's driven.

What is hard also is the symptoms can be very inconsistent and they can come and go. Car can behave one day, then the next day it doing things like the reservoir bubbling or overflowing, temp gauge acting weird, or no heat from the heater core. Sometimes these symptoms are accompanied by overheating and sometimes not. Usually before these symptoms you'll get oil or coolant peeping through the HG exterior, causing an oily mess on the bottom of the heads that gets on the exhaust manifold.

No need to vacuum fill these, in fact, as delicate as the head gaskets are, I wouldn't recommend doing that. The reverse pressure could open up a weak spot that otherwise would have been okay awhile longer.

I do encourage you to fix this and not dump the car, they're otherwise really great cars. Make sure you machine the heads at a quality machine shop when doing this and also use new head bolts and follow the entire tightening sequence in the service manual.