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Coolant System Bubble/High Pressure


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I noticed when starting up my LGT recently that it smelled a bit sweet, like some coolant had evaporated off the engine. Looking under the rad cap and the level was fairly low, such that squeezing the upper rad hose brought a bit of coolant into view and then back away. I topped it off with a funnel and went out to run some errands. Afterwards, I noticed that coolant had been blown out of the system through the reservoir and that the level was still fairly low under the cap again!

 

So I went and bought one of those spill proof radiator funnels, put the front of the car up on ramps, left coolant in the funnel and burped the system. Let the car cool off, and capped the radiator. This seemed to work really well and I thought that was the end of my problems.

 

The next day, I went out for a quick test drive, came back and had a look at the radiator. The upper hose had slightly unseated itself and it's starting to bubble (attached). Now this is where I'm a bit confused.. the system seems to have too much pressure in it, shown by the hose, but it's also not overflowing into the reservoir anymore. The level in the reservoir has not changed since I burped it with the spill proof funnel.

 

I let the car cool off, used a cloth to remove the radiator cap, and it shot coolant everywhere. Capped it off, got it up to temps, let it cool off and it again had too much pressure.

 

Since the hose has that bubble in it, I'm going to get a replacement next week from the dealership, but I'm wondering if there's something more I should be looking at? Should I do another coolant flush from top to bottom again?

IMG_20200709_095631.thumb.jpg.ed8e17c0e07c18b76e2d164c95c4d39f.jpg

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I noticed when starting up my LGT recently that it smelled a bit sweet, like some coolant had evaporated off the engine. Looking under the rad cap and the level was fairly low, such that squeezing the upper rad hose brought a bit of coolant into view and then back away. I topped it off with a funnel and went out to run some errands. Afterwards, I noticed that coolant had been blown out of the system through the reservoir and that the level was still fairly low under the cap again!

 

 

 

So I went and bought one of those spill proof radiator funnels, put the front of the car up on ramps, left coolant in the funnel and burped the system. Let the car cool off, and capped the radiator. This seemed to work really well and I thought that was the end of my problems.

 

 

 

The next day, I went out for a quick test drive, came back and had a look at the radiator. The upper hose had slightly unseated itself and it's starting to bubble (attached). Now this is where I'm a bit confused.. the system seems to have too much pressure in it, shown by the hose, but it's also not overflowing into the reservoir anymore. The level in the reservoir has not changed since I burped it with the spill proof funnel.

 

 

 

I let the car cool off, used a cloth to remove the radiator cap, and it shot coolant everywhere. Capped it off, got it up to temps, let it cool off and it again had too much pressure.

 

 

 

Since the hose has that bubble in it, I'm going to get a replacement next week from the dealership, but I'm wondering if there's something more I should be looking at? Should I do another coolant flush from top to bottom again?

Sounds like a head gasket failure.

 

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can check and see if the overflow nipple on the radiator is clogged, could explain the high pressure if the radiator cap is failed as well. You can check all of the hoses, the thermostat housing, crossover pipe on top of the engine etc to see if you have any visible leaks, but if the system is holding pressure that pretty much rules out leaks, and rules in head gaskets...
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I know with my Grand Prix, there would be some evidence of mixing fluids, i.e. dirty coolant or frothy muck under the oil cap. If I drain the coolant/oil, am I likely to see mixed fluids? Are there any other easy tests to confirm head gasket failure?
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generally, subaru head gasket leaks are from the coolant passages to the combustion chamber rather than between oil and coolant passages, so you're unlikely to have a mix of fluids. you can get/rent a coolant tester like this to test the coolant and see if it has combustion gasses present, if so that's a good indication that it's head gaskets.
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If its building pressure but not filling the reservoir, its likely the cap. You could have a head gasket failure causing the pressure, but that pressure should vent to the reservoir and blow coolant out there if the system is working correctly.

 

Early on, the cap should have allowed the radiator to refill when cool if working correctly too.

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Ok, so I acquired one of those combustion leak detectors, got the car heated up (interior temp set to HI on max), and tried for fifteen minutes to make the colour change without any luck. I did have to siphon out a fair amount of coolant since my first two tries ended up diluting the liquid. Torque app told me that my coolant was running about 200-203F. I also tried a couple minutes while pinching off the reservoir hose just to make sure I was pulling air from the radiator.

 

Start 5:05pm

 

attachment.php?attachmentid=285537&stc=1&d=1594417585

 

5:11pm

attachment.php?attachmentid=285538&stc=1&d=1594417585

 

5:14pm

attachment.php?attachmentid=285539&stc=1&d=1594417585

 

I had my wife come rev the engine a few times just to see if that would make a difference (not that I expected it to), and it didn't.

 

Discoloration:

attachment.php?attachmentid=285540&stc=1&d=1594417585

 

Now, I did turn the air back on and let the car idle some more while I tried to get the colour to change. I did get what seemed like extra liquid into the tester and it ended up discoloured, so I stopped.

 

What I think happened here was I was pulling air into the test kit, and I got some boiling coolant into the chamber, so it ended up evaporating off some of the coolant and/or test liquid. When I pulled the tester off the radiator inlet, the coolant level was pretty high and it was bubbling. Torque app said the coolant temperature was 217F so this makes sense to me. You can also see there's more condensation in the tester in this photo, which also explains why the level is slightly lower.

 

I'm thinking if there was actually a head gasket leak, it would have showed up pretty quickly. The test is pretty idiot proof, unless I'm just a really good idiot... :lol:

IMG_20200710_170514.thumb.jpg.bf5febc06d30ea11e3869770a824292c.jpg

IMG_20200710_171141.thumb.jpg.0e43641c0a0682e252638a6b9c730391.jpg

IMG_20200710_171427.thumb.jpg.10a9aaeff3214588fdac324d072f4814.jpg

IMG_20200710_172937.thumb.jpg.e9803e5b9393bb315aa965d02c7a57a4.jpg

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Ok, so I acquired one of those combustion leak detectors, got the car heated up (interior temp set to HI on max), and tried for fifteen minutes to make the colour change without any luck. I did have to siphon out a fair amount of coolant since my first two tries ended up diluting the liquid. Torque app told me that my coolant was running about 200-203F. I also tried a couple minutes while pinching off the reservoir hose just to make sure I was pulling air from the radiator.

 

 

 

Start 5:05pm

 

 

 

attachment.php?attachmentid=285537&stc=1&d=1594417585

 

 

 

5:11pm

 

attachment.php?attachmentid=285538&stc=1&d=1594417585

 

 

 

5:14pm

 

attachment.php?attachmentid=285539&stc=1&d=1594417585

 

 

 

I had my wife come rev the engine a few times just to see if that would make a difference (not that I expected it to), and it didn't.

 

 

 

Discoloration:

 

attachment.php?attachmentid=285540&stc=1&d=1594417585

 

 

 

Now, I did turn the air back on and let the car idle some more while I tried to get the colour to change. I did get what seemed like extra liquid into the tester and it ended up discoloured, so I stopped.

 

 

 

What I think happened here was I was pulling air into the test kit, and I got some boiling coolant into the chamber, so it ended up evaporating off some of the coolant and/or test liquid. When I pulled the tester off the radiator inlet, the coolant level was pretty high and it was bubbling. Torque app said the coolant temperature was 217F so this makes sense to me. You can also see there's more condensation in the tester in this photo, which also explains why the level is slightly lower.

 

 

 

I'm thinking if there was actually a head gasket leak, it would have showed up pretty quickly. The test is pretty idiot proof, unless I'm just a really good idiot... [emoji38]

Replace the cap and keep an eye on it. Those tests arent always accurate but let's hope in your case it is!

 

Sent from my SM-G965U using Tapatalk

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I have a similar issue going on but it seems like the coolant is at returning to the radiator instead.

I've heard sloshing when the car warms up as well so I'm trying all the cheap fixes before I go straight to the head gasket.

Did a flush, it's better but something still isn't right.

I ordered a new radiator cap from the dealership today. I'll update if this fixed the problem....

 

Sent from my Redmi 4X using Tapatalk

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My next course of action is replacing the cap and upper hose, since when I squeezed it, it definitely made a croaking/creaking sound that makes me think it's compromised...plus the goiter it grew can't be healthy!
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I tried the test kit again, this time I pulled the reservoir hose from the radiator and placed my finger over it just so it wasn't pulling outside air. I could get a few pulls from the bulb and then it formed a pretty good vacuum until I lifted my finger, so doesn't seem like there's extra gases in the system. The tester liquid stayed blue again.
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My last car did this. Bubbling coolant. I took it to several garages and they did that very same test and told me "nope, no issues at all. Drive on" but it kept overheating and kept bubbling. The overheating obviously made it worse and I eventually sold it as a lemon.

 

If there's pressure building in your coolant it means something is pumping it in. That something is your exhaust.

 

Mine didn't have mixing of oil and coolant either.

 

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I'd replace the upper radiator hose, put a new clamp on there (I have a t-bolt clamp there in my car) and look around for other leaks. (note - if you use a better clamp, don't go crazy with it - you are still clamping onto a plastic radiator outlet and you really don't want to break it! I was able to slide the hose back and forth on the nipple with the old clamp on there, so figured the clamp was done and put on something nicer than a worm drive)
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Sometimes with a small leak you won't notice it without load on the engine.

 

Drive up a hill, pull over and look for bubbles in the overflow bottle.

 

I had my wife rev the engine a bunch of times, hold it at 3000 rpm for 20 seconds, blip it to 4500/5000 rpm, etc. and still no sign of exhaust.

 

To look for bubbles in the overflow, can I just top off the reservoir without filling the system? Or will it just pull the overflow coolant back into the system.

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Borrowed a radiator pressure test kit, got the system up to ~11psi (black arrow I think is 0.8 bar), which I think is stock pressure.

 

It looks like it's dropping about 1 PSI / 10 minutes (these pictures were 11 minutes apart). My understanding is that if it drops 1+ PSI or more in a few minutes, then it's a head gasket leak. The very slow rate of leakage makes me think it could just be the tool giving off air. I didn't see any visible leaks while doing the test.

 

Thinking that the pressure in the coolant system could be escaping into the cylinders, I recorded starting the car and revving it a few times, but no white puff of smoke was seen.

 

Would it be worthwhile to leave the pressure test kit on and get the engine idling for a while to see how much pressure is building up, or is that not helpful to know at this point?

 

Short of doing a compression test on each cylinder, which seems like a pain in the arse, anything else I could look at?

IMG_20200712_172117.thumb.jpg.8013951c6c3a7e355c6eb539ecf040cf.jpg

IMG_20200712_173206.thumb.jpg.98249094cd03f4acfdcdae4f6e314859.jpg

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Here's a link to the video of the bubbles that occurred when I turned the temps down in the car so the AC ran instead of blowing heat on HI. Bubbling like this was not present when I was running the car with the heat blasting, so I suspect it's from the coolant temperature being increased (217F) and not from a HG leak...
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When my HGs went it was easy to reproduce the symptoms: top off radiator, get reservoir bottle to proper level, drive on highway for ten+ miles and the reservoir bottle would overflow. Once cooled down I would open the radiator and there would be an air pocket. For my DIY investigation I replaced the radiator cap and flushed the cooling system, no change.

 

https://legacygt.com/forums/showthread.php/add-me-gt-head-gasket-failure-list-255946.html?t=255946

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When my HGs went it was easy to reproduce the symptoms: top off radiator, get reservoir bottle to proper level, drive on highway for ten+ miles and the reservoir bottle would overflow. Once cooled down I would open the radiator and there would be an air pocket. For my DIY investigation I replaced the radiator cap and flushed the cooling system, no change.

 

https://legacygt.com/forums/showthread.php/add-me-gt-head-gasket-failure-list-255946.html?t=255946

 

Woah, that reservoir looks pretty... salty? :eek: You could grow stalagmites on it!

 

Did you have any signs of leaking from the gasket on the engine/head mating surface? I used my inspection mirror and it all looks clean on the underside, though I'll take a closer look next time I get the front end up.

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Yeah that was probably a coating of road salt.

 

I don’t recall seeing any external leaks. IIRC the dealer said they had a tough time confirming the gaskets were bad before tearing it down, whatever that means. I was still under the powertrain warranty so I presume the dealer has a diagnostic flow chart they have to follow to ensure reimbursement.

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You wouldn't expect to see an external leak, the issue is that the gasket is failing between the combustion chamber and the coolant jacket.

 

NVAKeith is right, drive on the highway for a while (or like I said, up a hill to get some decent load on the engine) and check your overflow bottle. Let the engine cool off and you would likely find the pocket of gas when you remove the radiator cap. It's a really simple test.

 

Early stages of head gasket issues.

Edited by moral hazard
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Got the new hose and rad cap this morning, installed the hose and burped the system again with the front end up on ramps. Filled the reservoir up to full? So far so good, the hose held its own. I got the temps up to 214F (then the fan kicked in and lowered it to about 200F) by turning the air off. The hose feels much more firm/rigid compared with the old one, even when pressurized. Also, it didn't try to slide off the radiator port as shown before.

 

I went for a 5km loop that was mostly city, with a quick jump on and off the highway. When I got home, there was no bubbling in the reservoir, and it was still at the full mark.

 

One thing I did notice was, I think I had the rad hose on 'backwards'. In the photos I posted before, there was a yellow dot and not an arrow on the radiator-side of the hose. The hose isn't 100% symmetrical and looking at photos from google images, it seems like the arrow should point towards the radiator. I suspect this might've caused some of my issues post-timing belt service that I did back in October.

 

This evening I was able to remove the rad cap without it being pressurized. I did notice the coolant in the reservoir appeared to be slightly lower than the full mark; I'll definitely be keeping an eye on this as I can't be sure it was perfectly at the full mark earlier in the day or not. I plan on taking it for a much longer drive in the next few days to dot the i's and cross the t's.

IMG_20200716_152242.thumb.jpg.97298db810d58855b1d1d56c50073e1c.jpg

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