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engine coolant system pressurizing

13K views 65 replies 10 participants last post by  boxterfan67 
#1 ·
I check my coolant level as often, if not more frequently, than most people check their oil. I start with checking the overflow level, then I check the coolant level in the radiator itself. Lately, I am experiencing intermittent pressurization of the system. The first time this happened was about 6 weeks ago. The overflow level was fine, but upon removing the radiator cap approx 4 oz of coolant burst out.

Transfer of coolant between the overflow and the radiator is occurring during operation, as it should. Temp gauge never goes above normal. Radiator, cap, and tstat were replaced in Dec. of last year. Let me add that this happening in the morning, after the car has sat overnight.

I'm stumped.
 
#2 ·
I think it maybe that HG thing you don't want to discuss at 200,000 miles?

see the 25 or so threads by @Lverano

I wonder if a petcock rad cap would help if you are getting a spray,...or a cap with a different pressure would help you drive it for a little longer before finding a replacement. or a back up car.
 
#3 ·
I've followed Lverano's posts. I may well have a HG problem, however, one would think that the exhaust gases introduced into the engine coolant would pass thru the cap into the overflow more readily than the coolant itself.

I was ready for you to ask this...however, until I have the coolant tested, I'll hold out hope.

As an aside, I've seen mentioned here a home test available to check for the presence of CO and other gases. I'd love more information on this test, unreliable as it may be.
 
#4 ·
#6 ·
cheap beater. = cheap beater. (as in cheap to buy, cheap to run,...something broke so what),...cheaper in aggravation then a cab.

4 cylinder 5 speed = a clutch that needs to be replaced,...

and them 6 cylinders like gas. (I knew someone with a 94 Camry 6 XLE,...and I can't remember if it took high octane).
 
#8 ·
I Let me add that this happening in the morning, after the car has sat overnight.

I'm stumped.
If your HG were leaking, any residual pressure in the system would bleed out through the leak and you would get a puff of smoke in the morning before the catalyst heats up. Is it possible that your engine temperature in the morning is still a bit higher than ambient?


If you don't have to add coolant and there are no signs of bubbles in the overflow, I would think that you have a plugged rad cap in the direction of discharge to the reservoir.....or your hoses are severely ballooned, but I think you mentioned replacing them recently.
 
#11 ·
Since 2012, I'm on rad cap #4. Every single coolant hose I can possibly reach has been replaced. Even went behind the dash to get one. Heater core flows fine, and doesn't leak. I probably made a mistake and did not replace one other hose behind the dash while I was in there, but no leaks.

Positively ambient temps. I'll park the car at 7pm and not go back to it for 12-16 hrs. Don't even need to open the cap anymore. When the problem decides to happen, I just squeeze one of the top hoses and can feel pressure.
 
#9 ·
have u tried changing the radiator cap? double check the tube from the rad to the o'flow is clear? (I'd think some pressure is normal - what? up to 16 psi?)

I have also had to use zipties to 'clamp' my o'flow tubes to that nipple at the rad neck. It was actually leaking on one of my cars.
 
#12 ·
I'm beginning to wonder if the d@mn Subagoo is gumming up my rad caps. I can see and feel the brown sticky crap it leaves behind. I believe it may impede the function of the cap.

As to ambient temps, I've left it where it would be in the shade the next day, and the sun as well...no pattern. Maybe rad caps are cheaper if I buy a case of them???
 
#10 ·
Have you given the radiator cap a good inspection to make sure the spring(s) and return valve are operating properly? Hard to imagine having problems with a new cap, but it could happen.

Is it possible that by the time you check it in the morning, the ambient air temperature is 10 or 15 degrees higher than the actual overnight low temperatures were? This could cause some pressurization in the cooling system, although 4 oz. of coolant (half a cup) sounds like a lot for this situation. EDIT: or, has the car had sun on the hood for a bit, heating up the engine compartment?

My 98 Forester has had the internal HG breach and bubbles in the overflow for about 1 year/7k miles now (has never overheated... and is coming off-line soon for a DIY HG replacment), and the coolant has NEVER been under pressure when the car is cold. The combustion gases get passed through to the overflow reservoir via the radiator cap, just like coolant does. Pressure is pressure, whether it be pressure in a fluid (coolant) or a gas (combustion gases). I suppose if the gas bubbles were getting stuck somewhere else in the cooling system (thermostat/WP area) and not making their way to the top of the radiator it could cause some funny symptoms... but you would probably have experienced overheating if the gases were forming a pocket in the thermostat area.

Also, since the combustion gases are a gas (vs. a fluid) they compress in volume when under pressure, meaning if you had an advanced internal HG breach you would typically notice a pocket of "air" (combustion gases) in the top of the radiator after the car cooled down and the pressure in the system reduced. You are getting quite the opposite - radiator is chuck full and under pressure, spitting coolant out when you take the cap off.
 
#13 ·
With the problem being intermittent, I really have no way to establish a baseline. Overflow tube is clear and free, cut at a 45° angle in the overflow reservoir. No leaks. As I posted above, the ambient temps haven't affected the occurrence. My working theory is that when the blue bottle garbage is killing my radiator caps.
 
#15 ·
The stop-leak crap causing the rad. cap to gum up is a good theory. I recently bought a 2000 Legacy and found a TON of that stuff in the bottom of the radiator, as well as the overflow reservoir... so it does end up everywhere in the cooling system. I removed the rad. and overflow bottle when I did the timing belt job on that car and flushed the gunk out of them. Also scrubbed the rad. cap with a stiff brush and Simple Green to get the crud out of the spring.

I refuse to put the stop-leak in my cars... just change the coolant every few years and run a few cycles of distilled H2O through it during the change.
 
#18 ·
@eagleeye, what color is your coolant when it has the coolant conditioner in it? If it's the color it was when it came out of the original bottle, it's different from mine. Mine has turned a dingy brown (really watered down coffee color??) and has a physical presence on everything.

I have another theory that has grown from a seed you planted in my head a good while ago, but I'm still in denial over that, even though the seed has sprouted and is now growing leaves, I think.
 
#20 ·
@eagleeye, what color is your coolant when it has the coolant conditioner in it? If it's the color it was when it came out of the original bottle, it's different from mine. Mine has turned a dingy brown (really watered down coffee color??) and has a physical presence on everything.

I have another theory that has grown from a seed you planted in my head a good while ago, but I'm still in denial over that, even though the seed has sprouted and is now growing leaves, I think.
mine in the H4 car is still a happy regular green color, no signs of age.

the H6 car has 60,000 miles of use on the prestone coolant, not additives and it looks its age, but not a problem. (its just change out time, I have OEM rad cap and thermostat in hand,...and I will ad a little bottle of the subaru magic too it at the time).

are you thinking one of the steel parts you may have has corroded from the inside ?

or Electrolysis like El Smarty: 1LT is on to.
 
#19 ·
interesting thread. i aslo wonder if you have a poor ground wire system and there is electrolytic corrosion going on? Or some corrosion from inside the aftermarket radiator? I have read that youu can put a voltmeter probe on the Neg batt term, and stick the other probe in the radiator neck into the coolant to look for excessive voltage. (how much is too much?)

I'd donate 5$ via paypal to a scheme where you send a sample of your coolant to Blackstone and/or Polaris labs for analysis.

if we get few more people, might be very cheap or free for you.

(always wondered if they could spot excessive combustion products , rust/corrosion, etc.)
 
#21 ·
The radiator cap only opens at a certain pressure. It's no surprise in general that there is pressure in the system that the cap isn't bleeding off - it's below the opening pressure.

But if the temperature you are checking it at is the same as the temperature you checked it at last time, something else is causing pressure other than temperature. There is really only a handful of options.

1) Chemical reaction
2) exhaust gasses pressurizing the system

I can't think of anything else that could cause pressure to be there at the same temperature as when the cap was last opened.
 
#24 ·
I have a kick@ss diagram and actual pics of where all 5000 grounds are on a Gen 2 car given to me by someone who shall remain nameless from me. Operator error is the largest margin of error in this whole charade. I'll freely admit that. I was pretty sure I got all the grounds clean when I did them last a coupla weeks ago. I'm about to go drive the thing after I go give it a once over.

Tex, I appreciate your offer, I sincerely do. But in my mind and in my heart I believe that I know what the base problem is, and I'll just have to deal with it instead of denying it every day. That said, I would still like to try one of those operator tests for CO and all the other wonderful gases that occur from burning gasoline and 10w30 oil. But until I get one of those (sounds like a frackin pregnancy test) I'm going to go over my grounds again and clean the cap again and do what's necessary to keep the thing rolling. I appreciate all of the support from all you guys, and would have blown the thing up had I not met all of you. So, off I go, and I'll check back in a little while.

Thanks
Fitz
 
#26 ·
Does your coffee coloured coolant look about like this? If yes, check out your ATF level. If your AT cooler has breached into your coolant it will cause the colour, (green + red) and will cause your pressure issues along with all the gummy goo you're seeing (oil + water). When it happened to me a couple of years ago the first thing I was thinking was a bad head gasket except the colour was wrong.
 

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#28 ·
what car was it?

got a schematic where exactly it rusts. (I think many of us would want to look at our cars right now,....or the next time they are up on a lift)

did you get any coolant in the ATF volume?
 
#34 ·
Subaru 38325AA032 Automatic Transmission Filter

when you are all done with this endeavor. (the ATF filter should have very little in it, if you have had no trans mechanical problems.)

cheapest I found for a ATF filter is Amazon. 28.19 free freight without prime,

(out of subarupartswarehoue = branford, CT,....and that amazon price even has their current 20% off memorial day sale beat "mem15" coupon code).

[ame]http://www.amazon.com/Subaru-38325AA032-Automatic-Transmission-Filter/dp/B00IGZQAZ0/ref=sr_1_1?ie=UTF8&qid=1432947368&sr=8-1&keywords=38325AA032[/ame]

although they seem to have them far cheaper on EBAY,...hopefully they are not knockoffs of the real mccoy

(the one I have in the garage, actually has the Tokyo Roki LFS706 number on one side of the casing and the subaru label and 38325AA032 number on the other.) ...got it from subarupartswarehouse of CT last year.
 
#35 ·
I read the discussion you and gen2lover had about filter #s. For OEM parts I usually use subarupartsforyou, and I don't have to be concerned with originality. But I have no intention whatsoever to pay $50 for an inline filter. I've never used Amazon, but have had an ebay store a few years ago. I'll research parts tomorrow, and see what's out there.
 
#36 ·
spin on filters is what I thought you were buying.

I never bought anything from EBay.

some of the store fronts at Amazon and EBay are actually subaru dealers, just looking for more outlets for their products if people don't find their own various web portals vs. other dealerships. (and only hunting on Amazon / Ebay).
 
#45 ·
if you look at the CSF website (in the link) the only 2002 one they sell with a aluminum tank is for a H4 car. "tank" = as they describe the actual material of the radiator I guess.
 

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#44 ·
To all those that guessed shoebox or bag, I'd love to say you're correct, but I don't know where it is except that I've seen it recently. I keep my maintenance records and expenses on my phone and do the work myself. I don't care about the paper receipts much.

I do know it took me almost a week to find someone that could get me an aftermarket radiator. That was before I knew about Rockauto.com. I could have spent a lot less if I had. I do remember being grateful to the only rad shop in town that would at least look for one and was successful.

I'd only been driving the car for about a month when this all happened to me. Grateful I wasn't driving any more than 25mph and under a mile and found out in my driveway.

I didn't know what was right or wrong with the car by its shift points and noises because I'd never sat in a Gen3 or heard what an H6 should drive and sound like. Every sound was different and foreign compared to the Forester and Gen2 Legacy I had been driving. This left me figuring that anything odd was just the different engine and trans.

My torque converter doesn't always unlock when it should and I've wondered on and off if the rad failure was why. Over time the TC has been better at unlocking when it should. I don't know if it was a problem before the rad failure or not. May have been an issue just not known it as I was pretty ignorant of how the car should behave.

I've seen one guy's pics of a 5EAT tear down after his cooler breached into his coolant and 4th and fifth gear clutches were fused and the drum had chunks missing.
 
#51 ·
The radiator I purchased off of ebay is made by a company called PBE Co. The model # is PR2465A.

I also bypassed the trans cooler using a small shunt and worm clamps. Capped the nipples of the trans cooler. I will drive to the doc this afternoon with the cooler bypassed to see how the car reacts, and if the ATF doesn't run hot then I'll perform a coolant flush and purchase yet ANOTHER radiator cap tomorrow, just to be sure. I'm struggling with the decision of whether or not to add a bottle of Subagoo this go-round. Since it's so cheap, I'm leaning toward having a bottle of it on hand, and making the decision to use it or not in the next couple of days. Any opinions? :banghead:
 
#52 ·
well, I have no idea of the efficacy but, if you feel the cooling system already has some 'goo' running around in it, you might consider leaving the conditioner out - or using half a bottle? Or doing some kind of flush and starting over with coolant and a bottle of conditioner?

you will have to make your self comfortable with whatever you decide - I don't think any of us here on the intertubes can get as good a 'feeling' about the issue as you can there with the car. Just keep in mind, it only helps with external leaks - weeping headgaskets or maybe a small leak at an old hose connection, etc. It will not help with 'typical' soob blown HGs. And you must not throw it in the overflow tank - follow the directions on the bottle.
 
#53 ·
did you find the box,....was the lost snorkel next to it? (or around/ under the porch).

I would get a bottle and just hold it.

the weather there says its 75F out now and will be 83F this afternoon. 76% humidity with a chance of thunderstorms.

so you can see how the vehicle performs. I would keep your tools in the hatch to see if you have to put the trans cooler back online in a parking lot.

__________

I wonder if you will need a different radiator in the end.
 
#54 ·
Yes, did find the box. No snorkel unfortunately. I have seen many pics here of EZ30D engines with and without snorkels. The advantage of having it is simply to force cool air into the passenger fenderwell, where the intake is located also. But the 2 parts do not directly connect.

Tools are always in the car, the essentials anyway.

The new rad looks and measures exactly the same as the Denso the car came with, I still have it for some reason. Hope to not replace it again.
 
#55 ·
I wouldn't use the conditioner. At least, not right now. You've put it in previously.

I would run straight water for now. You need to flush the goo out with something. Nothing is easier to do it with than a garden hose. Disconnect the lower hose, pull out the thermostat. Alternate putting liquid dishwasher detergent in each side of the engine run the hose water into each side of the engine. Dish soap will work as well but getting rid of the bubbles takes longer than getting rid of the mystery goo.

Municipal tap water isn't going to cause your engine any harm. If you have well water and you know there's some crazy amount of a mineral that is going to attack the block over time, it's still only temporary. It's equally a lot cheaper than coolant if it turns out you need to dump it. Water will pull more heat out of the engine than 50/50 mix but it can boil if the rad cap can't hold pressure. Cooling system pressurization of 16psi raises the boiling point to 216F/102C. Your engine likely runs at 200-203F/93-95C. If there's no cooling issues, besides what you suspect, the water will not boil. No boil, no problem. Save money on coolant until you know what's going on. Once you know what's going on and everything is fixed or was nothing, put the conditioner in along with new coolant.
 
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#56 ·
Municipal tap water isn't going to cause your engine any harm. If you have well water and you know there's some crazy amount of a mineral that is going to attack the block over time, it's still only temporary.
I know a municipality that has their water a little cloudy with light yellow red clay. the water district there is part of a town a with a village, and they don't have money to filter the particulates out.


cloudy enough,...just enough to make you wonder. ...it does not taste bad and I guess it is not "dangerous" just very very cloudy out of the tap, and some businesses have yet to discover what filters work on the matter....coffee tastes OK though.

I have filtered well water, which I could probably bottle and sell legally.....and I got a couple gallons of distilled water to flush through the idling car for 15 minutes when I do a coolant swap. (maybe get some solids out)
 
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