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Subaru Forester 2007 -- Valve Cover or Head Gasket Leak?

Hi All,

First time poster here – I’m also a complete novice with cars! Just got my oil changed at a garage in Boulder, and they noticed that my coolant reservoir was really full, but they’re unsure whether or not my valve cover or my head gaskets are leaking. The reservoir was reset; the mechanic advised that I drive back to Denver (~30 miles). If the level had risen once I got back to Denver, she said that I may or may not have a head gasket issue.

I’m the third owner of the vehicle, has 130K, and the head gaskets were replaced when I bought the car (approx. 1 year ago). The radiator busted over the winter, so that is also brand new.

The question: Is there any way to tell if this is a Valve Cover or Head Gasket issue without taking it into a shop? And what should I be doing/monitoring in the mean time? I will have to drive this back out to CA next summer, so I need this thing to last!

Thanks all!

Easy, valve cover gasket has nothing to do with coolant reservoir. Step 2 find a better mechanic. Keep an eye on coolant level and if your oil looks like anything but oil stop driving it and see if who ever did the head gasket will warranty the work.

When the engine is cold, remove the radiator cap.

Check the coolant level. If the coolant level is low add coolant.

Start the engine and as the engine idles watch the coolant in the radiator.

If bubbles begin to appear in the coolant as the engine idles, that’s an indication of a leaking head gasket.


Good ideas above.

When the radiator burst the last time, did you notice if the engine overheated? If so, that can compromise the head gasket. If you decide to visit a shop for a proper diagnosis, be sure to tell your mechanic about that incident.

It’s possible of course there’s nothing wrong, just someone over-filled the cooling system at some point. That’s easy enough to rectify. Besides the ideas posted above, ask your mechanic to check for

  • signs of coolant in the oil
  • signs of oil in the coolant (e.g. cottage cheese like gunk on the inside of the radiator cap)
  • the specific gravity of the coolant to insure you have the proper mix

Besides monitoring the oil and coolant levels, good idea to also monitor the dash coolant temp gauge and if it goes significantly above where it normally resides, meaning the engine is overheating, turn off the AC, turn on the passenger compartment heater to hot and the heater blower to max, that can provide some engine cooling until you can pull over and get the car towed.

"find a better mechanic"

If this so-called “mechanic” isn’t working at a quick-lube place, then she should be, because nobody who is a qualified mechanic would be under the impression that a leaking valve cover gasket would have any effect on the coolant level.

Was this diagnosis done at a quick lube place?

2nd owner had headgaskets issue. Either fixed car and sold it or sold it to next guy. A burst rad can be due to over pressurized cooling system. Did it blow fast or leak slow? OP don’t say which. Might have been small leak. And no overheating issue.

You didnt fully explain the issue with your old radiator…and unless you smashed into something…what you are describing could be an overpressure event in the rad…which only happens when head gaskets fail.

A quick test is like Tester mentioned… and or…feel your rad hoses when the engine is hot… Give them a squeeze…they should not be Hard…or feel too firm or overpressured… This is a quick test I always perform and when you are familiar with how firm a hose should be…you can quickly tell if your hoses are overpressured.

When I find an overpressure… I always release the rad pressure and then leave the rad cap loose until I am able to do the proper repairs…this prevents the rad from being damaged…and also prevents coolant contamination of your motor oil… It lessens the pressure put on the entire system.

Methinks you may have been lied to about the Gaskets being done…or done properly that is. Many morons out there…who will do the head gaskets without checking the cyl head for Squareness prior to slapping new gaskets on…the result? Failed Head Gaskets.

I agree with pretty much all the advice you were given above…


Whoah, so many great responses. Thanks all! I’ll respond to each individually below –

Barkydog – Are there any specific colors/textures I should look for when I check the oil dipstick?

Tester: I just ran your test, but totally forgot to leave the radiator cap off. Will report back tomorrow morning when I re-do it.

GeorgeSanJose Yes, I was about to get on the highway when I noticed my temp. gauge running up and down like mad. Brought it into my shop (NOT the shop mentioned in my first post), and they said my radiator was busted. It’s been about 5-6 months since the radiator was replaced, and I haven’t had any issues with the temperature since.

Re: over-filled cooling system & my first post – When they reset my reservoir, it was still WELL above the “FULL” line. Please advise.

I did look under the radiator cap just now – no gunk detected.

VDCdriver – Not sure if she meant to point out an associative rather than a causative link. It’s a small, full-service shop attached to a gas station.

Cavell – Not really sure, as I hadn’t worried about my radiator until I noticed my temp. gauge on the fritz. There were no overheating issues prior to that incident ~5-6 months ago. The head gaskets were replaced by the used-car dealer – who used the machine shop across the road; on hindsight, I should’ve yelped them! – after I got a third-party inspection at Subaru dealership, who noticed something that may or may not have indicated a gasket issue.

Honda Blackbird – I hope the above replies (especially to Cavell’s and GeorgeSanJose’s) help further contextualize the issue w/ my radiator. I am also thinking that it was either a) mediocre mechanic workmanship, b) mediocre machinist workmanship, or c) a combination of both.

Again, I will try Tester’s test once more tomorrow morning – this time, I won’t forget to leave the cap off and check for bubbles! Thanks all for your help. 'Til tomorrow.


You temp needle already suggest the likely results of Testers Bubble test… The prior rad seems to have died from an overpressure with no prior collision to it…and the temp needle is dancing because of air pockets in the coolant system…pumped in by a head gasket pressure breach…

ALL symptoms you dont want…

I have diagnosed and repaired at the very least 30 of these vehicles…all with the same symptoms…all needing head gaskets AND machine work on the head to ensure “square”…methinks someone skipped a step…or never did what they said.

I hope I am wrong…its been known to happen…but you are reading us chapters of the “Blown Head Gasket Blues Book” as far as I’m concerned…

Do your due diligence and let us know your test results


Gotta go wirh @“Honda Blackbird” as far as the oil, a little blackish is fine, anything similar to a milkshake is bad.

Hey all,

The car cooled down enough since my last post and now to re-run the test. This time I did it correctly. Also attached some photos.

Photo 1: Level of coolant visibly present before the I turned it on. Seems really low, like, too low. Right?

Photo 2: The amount of coolant in the reservoir. The black line in sharpie marked the level before I drove it back to Denver the other day (scenario mentioned in my first post). WAY too full, right? That bottom seam is the “FULL” line, but you all probably know that already.

Photo 3: Level of coolant visibly present with the car turned on.

OK – I let it idle at temp for about seven minutes. Vapor escaped, but no bubbles. I also monitored the reservoir tank for bubbling, and there wasn’t any. Not even tiny ones. I also gave the big radiator pump and the smaller one (leading to the reservoir) a squeeze. They weren’t firm at all to the touch.

I’m relieved, but also worried, because I have no idea what this means.

Again, major thanks to all of you!


The radiator cap might be bad, the return hose might be bad, the radiator should have no air in it if the radiator cap and return coolant hose are functioning properly

Looks normal to me. If the radiator is being filled to the brim while the engine is cold heat will cause the coolant to expand and it will burp coolant out into the overflow bottle past the radiator cap.
Try replacing the radiator pressure cap. Those caps can be tested with a cooling system pressure tester.
AutoZone may, or may not, have a cooling system pressure tester as part of their free loaner tool program. They may even check the cap for you. I’m not familiar with how far AZ will go in checking things.

@Barkydog – The radiator is less than a year old, and I assume new caps come with them?

@ok4450 – OK, cool. Thanks.

Is that the pressure cap the top cap?

If a new cap is on your receipt then you have a new one. Otherwise it is a question for whoever did the repair, or assume not. It would be the cap on the radiator itself.

The pressure cap to replace as a test is the one that fits on top of the radiator. Definitely worth a try as new ones are inexpensive.

I can’t speak to the Forrester, but on my Corolla the radiator itself always appears filled to the brim. Coolant moves between the radiator and the overflow tank depending on the engine temperature. But the radiator always looks completely full.

Also if the hose is clogged or failed it will suck air rather than coolant into the radiator,

I see no evidence of the gump in the coolant that would typically be present with a bad headgasket, which would allow combustion gasses to blow into the water jacket and contaminate the coolant. The coolant and the insides of the radiator look clear and clean.

Your reservoir will have two levels in it; one for when the engine is cold, and another higher one when the engine is at operating temperature. Coolant expands considerably when heated and the level rises. Your amount of change looks normal to me.

The way the system works is that as the coolant heats up and expands in the engine beyond about (typically) 15psi the fluid is pushed past the radiator cap and into the reservoir. When the engine cools again, the coolant is drawn freely back into the engine past the cap. The tube on the right side of the fill hole in the photo is the one through which the fluid moves, and the coolant level looks to be at that level in both photos, so I don’t see a problem.

Everything I see and everything I’m reading suggests that your only problem is having heard from a wannabe who really didn’t know what he was talking about. Since he’s the one who changed your oil, check your oil level immediately and monitor it for a few days… and keep your eyes peeled for any signs of an oil leak. He may not have filled the oil properly, or may have failed to tighten the plug properly.

Check your tranny fluid level immediately too. Just in case he drained that instead of your oil.

Yes, the pressure cap is the top cap on the radiator; the twist off one. As far as I know radiators don’t come with new caps; at least I’ve never seen or bought one that way.

Rather than pressure checks, caps are cheap and you could just replace it. Just my 2 cents, but I’m of the opinion that any radiator replacement should mean a new cap also.