('03-'05) Was overheating, added coolant, not overheating any more but ... - Subaru Forester Owners Forum
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post #1 of 15 (permalink) Old 06-13-2019, 04:16 PM Thread Starter
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Cool Was overheating, added coolant, not overheating any more but ...

(My very 1st post so go easy on me!) EJ25 at 140k, with HG and water pump replaced at 80k, new radiator and cap a year ago. Was overheating after warmed up while at idle for 10 minutes with air on, even on a cooler evening. My temp gauge never rises above half unless there's a problem. Once it does it will keep rising. I found that revving engine to 1.5-2k would immediately bring the temp back down - like in 10 seconds. Also when i turned the AC cold over to heat - very hot air poured into the cabin. Reading your forums I suspected HG failure, air pockets, low coolant, stat, you know the drill. Well, sure enough, I was about a half gal low on coolant, even though the expansion tank was full. Filled her up and no more overheating, at least for a day, and I ran it quite a bit.

But, please tell me - I'm in Florida and it's hot here and I've been running this engine for 40 min with the air on, I come home, and 5 min after shutting her down I remove the radiator cap with a towel, I notice just a little pressure release when I do, I start the engine and run it with the cap off, and there is just a gentle water flow inside the radiator. (Now I just filled it to the top this morning.) I am expecting this thing to be steaming hot, bubbling over, and at the least overflowing out the top of the radiator, but no - only when I rev the engine will it bubble up and begin to overflow out of the open radiator opening. Quite a few air bubbles appeared present as it bubbled over the opening. The top rad hose was hot, the lower hose almost cold. I measured the water temp thru the open radiator hole with my wife's meat thermometer and it says 194F. I measured the expansion tank water at about 175F.

So I have 2 concerns. I did lose coolant - but perhaps this was over several months time so perhaps no worries? And - is my coolant circulation as strong as it should be? Is that stat working properly? It just seems like so little circulation for what I presumed to be a hot engine? I guess the engine really wasn't that hot?

I ordered a coolant combustible gas tester and some UV coolant dye and will test accordingly.

I really appreciate anyone's thoughts.

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post #2 of 15 (permalink) Old 06-13-2019, 04:25 PM
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Sounds like you might have a thermostat stuck open.

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post #3 of 15 (permalink) Old 06-13-2019, 04:53 PM Thread Starter
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Thanks for your quick response, Bill. - which leads me to 2 more questions. If the t-stat were working properly, how would my coolant flow / open cap behavior look differently? Secondly, is the t-stat replacement on this vehicle doable for a shade-tree diy'r computer geek? I've done the job on my former 2000 Nissan Quest (RIP) and over-tightened a bolt while learning a valuable lesson on that one.
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post #4 of 15 (permalink) Old 06-13-2019, 05:39 PM
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Quote:
Originally Posted by SubeFan61 View Post
"Was overheating after warmed up while at idle for 10 minutes with air on, even on a cooler evening. My temp gauge never rises above half unless there's a problem. Once it does it will keep rising. I found that revving engine to 1.5-2k would immediately bring the temp back down - like in 10 seconds."

" only when I rev the engine will it bubble up and begin to overflow out of the open radiator opening. Quite a few air bubbles appeared present as it bubbled over the opening. The top rad hose was hot, the lower hose almost cold. "
I reduced your quote to the things that mean the most to me.

Reving the engine up and the resultant drop in temp means that at idle RPM you are not moving the coolant, but at higher RPM you are. Back in the day, fans were crank driven. But now, of course they are electrical, so that cannot be the explanation. Instead, I suspect that you have either a bad water pump, OR, you are having exhaust gasses leak into the water jacket and they are building up around the temp sensor. When you rev it up, the circulation of coolant improves, the temp sensor gets covered with coolant and your temp gauge falls.

The second quote supports my second theory. You should NOT get overflow out of the open radiator opening with reving the engine. All those bubbles I suspect are exhaust gasses.

Finally, you are running a proper 50:50 mix of glycol and water, right? Cause pure or low glycol mix will boil at a lower temp and then I havn't the slightest clue how your boil points will be effected when you observe things with the radiator cap off.

People who read my posts will known that I am mister doomsayer when it comes to HG issues. So for your sake, I hope I am wrong. I suspect its HG. But I have been wrong sometimes.....
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post #5 of 15 (permalink) Old 06-13-2019, 05:41 PM
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If your coolant was heating up to normal operating temperature I would expect a lot more pressure when you removed the radiator cap after waiting 5 minutes after a 40 minute drive. When a thermostat is stuck open the engine and coolant run cool. However, I think you would notice that on your temperature gauge. I never replaced a thermostat myself (had mechanic do it in conjunction with timing belt package) but I'm sure someone on this board can give you some "shade tree" advice. Anyone?

If you are still running the factory thermostat and radiator cap I would replace both as preventative maintenance, even if they are not the source of your current problem. Both are relatively cheap especially if you DIY.
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post #6 of 15 (permalink) Old 06-13-2019, 06:00 PM Thread Starter
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here is what it looks like ... might have to copy and paste it

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post #7 of 15 (permalink) Old 06-13-2019, 08:08 PM
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Replacing a thermostat on a 2003 XS is a straight forward job:
A: REMOVAL
1) Set the vehicle on a lift.
2) Lift-up the vehicle.
3) Remove the under cover.
4) Drain the engine coolant completely.
5) Disconnect the radiator outlet hose from thermostat cover.
6) Remove the thermostat cover and gasket, and pull out the thermostat.
B: INSTALLATION
1) Install the thermostat in the water pump, and then install the thermostat cover together with a gasket.
NOTE:
• When reinstalling the thermostat, use a new gasket.
• The thermostat must be installed with the jiggle pin facing to front side.
Tightening torque:
6.5 N·m (0.65 kgf-m, 4.7 ft-lb)
3) Reconnect the radiator hose
2) Fill engine coolant.
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post #8 of 15 (permalink) Old 06-15-2019, 02:44 PM Thread Starter
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Thank you all for the advice. My 'combustible gas in the coolant detector' arrived today so I''ll quickly determine if CDHerman is correct about the head gasket leaking - he's probably right. After filling up with 50/50 a couple days ago, the car no longer overheats, and running too cool in Florida isn't a big concern of mine, but it sure is odd to me, so I appreciate the possible cause on that one. I'll also watch how quickly I lose coolant. I'll report back in a couple weeks with my results and hopefully my experience will help someone else.
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post #9 of 15 (permalink) Old 06-15-2019, 03:45 PM
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I can't solve your problem, but here are a few things to consider. Your cooling system has more than enough capacity to cool the engine - even in Florida, and even if the system is not pressurized (that is, you have a small radiator seam leak). So, if you are experiencing overheating and there is no other obvious issue, it's likely to be a head gasket. Even a small injection of combustion gasses into the cooling system will cause overheating. A leaking radiator (resulting in no or low pressure) will probably not cause overheating.

As for the thermostat, if it is stuck open, you would expect the engine to warm up more slowly. But, other than that, it really should not matter. If working properly, the thermostat opens rather quickly, and 'open' is 'open'.

If the thermostat is stuck closed, it could cause overheating. But there should be a by-pass hole in the thermostat frame, so some coolant will still circulate.

Finally, the cooling system should be 'closed' system - nothing entering or leaving. So, if you fill the radiator and overflow (and mark the overflow level), the overflow level should rise with the engine is hot, and return to it's original level when the engine cools down. If the level in the overflow starts going down over time, you have leak . . . period. Find that leak.

Again, it could be a head gasket, but it could also be a leaking radiator. Subaru plastic radiators of your vintage have a finite life. At 140k, you're on borrowed time. The leaks can be hard to find, but if you're driving hard on the highway, then pull off and immediately pop the hood, that's the time of maximum coolant temperature and pressure. Look along the top and bottom radiator seams (where the top or bottom tank joins the core). Look for 'steam' rising from the engine. Also, look for any coolant splatter on the front or top of the engine. It may be hard to see because air flow when driving tends to dry the splattered coolant.


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post #10 of 15 (permalink) Old 06-17-2019, 08:56 AM Thread Starter
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Thanks Dave, Kevin, Bill, and CDHerman for your insight. I've got some checking to do. I'll report back my results.

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post #11 of 15 (permalink) Old 07-01-2019, 04:44 PM Thread Starter
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Ok Dave, Kevin, Bill, CDHerman, and Kevin - I'm back as promised. It looks like (as usual) CDHerman and Dave5358 know what they are talking about and nailed it on every point. Since the vehicle was overheating, was loosing coolant, and overheated more at idle that while not, the head gasket was a prime suspect. I kept reading how typically everyone (or your uninformed or opportunistic mechanic) runs out and buys a new water pump, thermostat, or radiator cap - but I decided not.

Now since my last post, I topped it off with 50/50 coolant and I've been driving like a madman for 2 weeks without a hiccup in hot SW Florida, but today I was on a longer interstate journey (about 30 miles north) and it did well until I pulled into town and then the temp shot up. I can usual coax the temp down by rev-ing it to 2k and/or turning on the heater which is super hot, btw. I got to where I needed to and then another 40 miles home, but slowed down a bit on the interstate. It's when you come to a stop that the temp goes crazy. At home I found that it had lost about a half gallon from my radiator - in the past 2 weeks that is. I believe it's been boiling out the overflow tank which his always near full. (and this might be another teaching point - when the car cooled, my top and bottom rad hoses were sucked in by a vacuum - which released when I took the cap off. I witnessed that behavior twice. Perhaps my rad cap was not allowing the overflow tank to flow back into the system as it should? - maybe, but that's another story.

I thought, why not cut to the chase and go after the prime suspect - the head gasket? I mean TEST IT! Mine had already failed several 60-70k miles earlier. So yes, I purchased from Amazon a 'combustible gas in the coolant detector' called a Block Tester for $36. It comes with enough fluid for about 5 uses. You stuff it in the radiator cap opening with a hot engine, and you suck the fumes up into it and through the blue liquid with its syphon bulb. It's starts out as blue and turns green or yellow if it's your unlucky day and exhaust is leaking through the head gasket into your coolant. Best $36 I ever spent. You can watch the video and decide if I need a new head gasket. Thank you everyone and I hope my experience helps others.

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post #12 of 15 (permalink) Old 07-01-2019, 05:03 PM Thread Starter
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And here's what it looks like when you rev it:

https://youtu.be/2IegGu9cv88
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post #13 of 15 (permalink) Old 07-01-2019, 07:52 PM
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It didn't turn real yellow, but was getting greener and less blue. I am not sure if you have decided that your HG is blown or not. I suspect it is. The episodic bubbles looked pretty much like mine did. I mean what are those bubbles? If the are steam, then the engine should have been hot.

One point however, the observation that your hoses are collapsed when cool COULD REALLY POINT TO A DIFFERENT CULPRIT. Your rad cap, the overflow hose or the overflow tank could have an obstruction. Hoses should not collapse and leave fluid still in the overflow tank.

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post #14 of 15 (permalink) Old 07-02-2019, 04:34 AM Thread Starter
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I've pretty much decided that the HG is leaking, injecting hot exhaust gasses into the coolant, and creating an air pocket around the thermostat and/or temp sender that's shooting up the temp. Increasing the rpm boosts the water pump flow and temporarily clears the air pocket (and improves cooling in general) and the temp drops back down to normal. The key there is - I can watch the temp gauge drop like a rock when I rev it. The other thing is - I'm loosing coolant, and this is a new rad and cap (1 year old), but it's always wet around the overflow tank. Also - unlike the last time, when I took the rad cap off my hot engine - it was real hot and lots of steam came out - my top and bottom hose were hard and hot, so there is lots of pressure in the system and perhaps not leaking bad in that regard. Also - there are always some bubbles active in the overflow tank during this overheating. Now I totally agree that the rad cap/overflow system is not working properly because it's not allowing the full overflow tank to suck back into the system when cooled. I don't have an obstruction, so I have to assume the the rad cap is not doing it's job. Apparently the rad cap has 2 jobs: 1 is to sense when there is 16lbs of (steam) pressure in my system and allow it to overflow into the overflow tank, and the other is another valve in the cap in the opposite direction that would open when the system has negative pressure after cooling and would open and allow that full overflow tank coolant to be sucked back into the system - and that is not happening. so who knows if the rad cap problem is playing a bigger part in my issues? Perhaps I could get by much longer with a properly functioning rad cap? So I could buy a new cap, get my coolant in perfect condition again, purge out the air, and see what happens?

My understanding was - if the coolant / combustion test turns green (which it did)- I have a HG leak, period.

Thank you everyone for your insight.
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post #15 of 15 (permalink) Old 07-02-2019, 01:17 PM
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I agree that taken as a whole, what you are describing is a HG leak. The longer you run coolant through the valves, the more you will damage the valve seats and guides (leading to more expensive cylinder head repairs.).

Guess you got 60k miles out a HG. That's better than the 20k I got with my HG replaced at 124k, which made it only to 144k miles. I don' t know if you know the whole history of your Foz. I sure didn't. I really suspect that there are "hot potato" vehicles out there that have had the HG replaced several times, then traded when the owner realizes that the HG is gone again after a disappointing number of miles. I am nearly certain I am on the 3rd or 4th replacement. Maybe I did it right this time.

If you do it, or have someone do it, FORCE them to not only true the heads, but put a quality straight edge on the block as well. if you can pass a .002 feeler under the straight edge, even partially, then the cylinder edges of the block are rounded or low. No HG will ever fix that. The "wiz wheels" that shops used are FINE for a cast iron block. And they ruin aluminum blocks.

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