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98 Legacy 2.5L loosing coolant and overheating
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stevenal
New User
Mar 5, 2013, 2:30 PM
Post #1 of 13
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98 Legacy 2.5L loosing coolant and overheating
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I'm losing coolant out of the overflow to the point the heater stops working and the needle starts to climb. In the driveway it only bubbles a bit, but a few miles on the road will blow the coolant out.
First I replaced the cap since the gasket looked off center. No joy. Performed system pressure test, and system holds pressure for hours and no leaks evident. Also no wiggling of the gauger with engine running. Exhaust appears normal.
I bought a block tester and used it. With coolant bubbling well, indicator remained blue.
Radiator looked rotten, so I replaced it. Also replaced hoses and stat, flushed and filled coolant. Dumped coolant looks clean. Still barfs coolant on the road.
Changed oil, no coolant present.
I believe I've narrowed it to head gasket or water pump, but am unsure how to narrow it further. Can a head gasket problem cause bubbles with no combustion products? Can a bad pump have suction leaks and still hold pressure?
I've been careful to purge the system upon every refill. Any thoughts? Thanks.
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Hammer Time
Ultimate Carjunky
/ Moderator
Mar 5, 2013, 4:15 PM
Post #2 of 13
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Re: 98 Legacy 2.5L loosing coolant and overheating
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What is the temp of the engine when this is happening?
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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speed
User
Mar 5, 2013, 4:16 PM
Post #3 of 13
(1480 views)
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Re: 98 Legacy 2.5L loosing coolant and overheating
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Is your cooling fan working? it should be turning on if your coolant is getting that hot and it should kick on with your A/C on.
GM ASEP 26 SCC Milford ASE certified in Brakes and Electrical on Thursday April 5th 2012
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Hammer Time
Ultimate Carjunky
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Mar 5, 2013, 4:20 PM
Post #4 of 13
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Re: 98 Legacy 2.5L loosing coolant and overheating
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We don't know that it's getting hot yet Speed. That's why I asked the question.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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speed
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Mar 5, 2013, 4:22 PM
Post #5 of 13
(1470 views)
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Re: 98 Legacy 2.5L loosing coolant and overheating
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Sorry you beat me to submitting my post yours wasnt there when i posted it but i only asked because they said the coolant is getting hot enough to bubble and boil out of the overflow tank.
GM ASEP 26 SCC Milford ASE certified in Brakes and Electrical on Thursday April 5th 2012
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stevenal
New User
Mar 5, 2013, 4:32 PM
Post #7 of 13
(1455 views)
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Re: 98 Legacy 2.5L loosing coolant and overheating
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I'm not sure how the gauge is calibrated. It reads low to mid-band until the heater stops putting out warm air, then starts to climb up to "hot." At "hot" I tend to shut down.
Fans cycle on and off as they should.
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Hammer Time
Ultimate Carjunky
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Mar 5, 2013, 4:50 PM
Post #8 of 13
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Re: 98 Legacy 2.5L loosing coolant and overheating
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Since you already replaced the cap, it sounds like you are getting combustion gasses into the cooling system, likely from a blown head gasket.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
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Mar 5, 2013, 4:52 PM
Post #9 of 13
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Re: 98 Legacy 2.5L loosing coolant and overheating
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Just notes: Heater will not throw warm air if air is in the core or overheating to the point of boiling. I tend to think waterpump is pumping or heater would be lousy from lack of good flow when it does work.
This could hold pressure with that test but not hold combustion pressure but you said that tested good. I don't think that test was conclusive somehow? Need to know actual temp at thermostat housing still but kinda think you are getting combustion gases in thru a head gasket or anywhere that those pressures exceed (way up there) any cooling system normal pressures and those gasses are the problem. Guess so far.
You might notice by squeezing upper radiator hose upon cold start that pressure builds fast - not a good sign. How fast is fast? That depends on several factors. If before warmed up you released pressure at pressure cap and pressure returned that would be damning too for head gasket problems.
Do anything not to let this get truly hot or it could mean more problems than the problem at hand,
Tom
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stevenal
New User
Mar 5, 2013, 5:14 PM
Post #10 of 13
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Re: 98 Legacy 2.5L loosing coolant and overheating
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I've done the block test several times now with the same result. I suppose I could test at the tailpipe to make sure the fluid is good. But is combustion gas the only possible head gasket problem that would cause bubbles? Or could air leak in?
I agree the pump is working initially. I wonder if a suction leak might be occurring causing it to ventilate and stop pumping.
I have not observed a rapid pressure rise, either with the gauge or by squeezing the hose.
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Hammer Time
Ultimate Carjunky
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Mar 5, 2013, 5:18 PM
Post #11 of 13
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Re: 98 Legacy 2.5L loosing coolant and overheating
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Let me tell you something. In the last 20 years I have diagnosed and or repaired in excess of 100 blown head gasket situations and not one of them failed the chemical test. As far as I'm concerned, that test is worthless. If you really want to find out, find a shop with an exhaust gas analyzer and sniff the fumes at the radiator cap on a hot engine and look for a hydrocarbon reading.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
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Mar 5, 2013, 5:20 PM
Post #12 of 13
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Re: 98 Legacy 2.5L loosing coolant and overheating
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Air isn't leaking in but probably the high pressures of combustion act just like air in the system. I don't know why you test isn't working??
T
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Discretesignals
Ultimate Carjunky
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Mar 5, 2013, 6:31 PM
Post #13 of 13
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Re: 98 Legacy 2.5L loosing coolant and overheating
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Leak down test might reveal a blown gasket. Subarus in those years are known head gasket blowers.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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