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Posted 05 August 2003 - 10:28 AM
'99 Impreza, 2.2 L, 150K miles.
Ive suspected a blown head gasket, the coolant was brown, and when it sat long enough, oil floated to the top.
Then the car started overheating... not steaming, but hitting the top of the max-normal range.
Dealer did a coolant pressure check and didnt find any pressure loss, so the dealer doesnt think the head gasket is bad. Radiator was cool at the bottom but hot on top, suggested a new radiator.
Local mechanic not so sure, suggested a flush/fill. Did that with new thermostat and drove to work, 65 miles and 90 mins. away.
After about 30 mins. the engine started running warm, and began to hit max-normal. Got gas at a gas station, released pressure in the radiator with a pressure-relief valve in the radiator cap, and the temperature dropped to normal.
Continued into work, the temp. increased to max-normal again. Got to work, "burped" the radiator again, and the temp returned to normal.
Soooo... any ideas what is going on? The fans are coming on. No sign of leakage from the water pump. If the radiator were plugged, this should have shown itself during the flush... BUT no steam is seen at startup, so that means no coolant in the combustion chamber....
Thanks for any thoughts!!
Guest_1 Lucky Texan_*
Posted 05 August 2003 - 10:43 AM
I only can think of 2, head gasket leak or a human put some in there. Any teens or incompetents maintaining your car?
1 Lucky Texan
Posted 05 August 2003 - 10:53 AM
i called a radiator shop, and they said it would be $40 to check for gasses, $75 to diagnose it the whole way. since the parts to replace it are not too much more, i just went for it, and skipped the test (i've got bubbles & a slight oily sheen in the coolant). my parts should be here tomorrow so i'm pulling the engine tonight.
another test that can be done it to remove all of the spark plugs, put a test cap on the radiator that allows the system to be pressurized, then hook it up to ~ 10lbs of shop air. after a few hours, coolant should fill part of a cylinder. when you crank it, the coolant will spray out the spark plug hole. it does seem like the head gasket is bad, though. hope this helps...
also. here is a possible explanation to the over heating that i found somewhere else and posted...
Posted 05 August 2003 - 02:14 PM
My 1990 EJ22 starting overheating in a similar fashion, though no oil in the coolant. A tiny sipe in the head gasket from combustion chamber to coolant was allowing compression gas to slip into coolant. No problems in city driving, but after long highway trips the temp would rise quickly, usually not into the red - like yours.
My theory is this: Lots of little gas bubbles in the coolant aren't a problem when you're cruising at 4000rpm, they just circulate. As soon as the engine drops to idle in slow traffic, the bubbles tend to collect in the water pump. Why? Pressure drop allows them to expand and join up...leading to a big gas pocket in the pump and no circulation....temperature rises....engine off, the bubble can be "burped" out...and you're okay for a while again.
This is how most high quality head gaskets start to fail. Slowly it gets worse, and eventually oil and coolant mix.
Cheap gaskets tend to blow oil out between head and block and into the coolant, then they just seem to collapse. These failures easily show up in compression tests.
Posted 05 August 2003 - 02:24 PM
Well, no teens in the area.. at least the dogs would keep most away... as for incompetents servicing the car.. that is strongly possible since I do the oil changes myself...<g> but I try to avoid getting oil in the radiator...
Posted 05 August 2003 - 02:33 PM
Yes, when I burp the system, bubbles appear in the expansion tank.
No test was done for exhaust gasses in the coolant, the local mech doesnt have the equipment. That was the main reason for going to the dealer. The dealer "pressurized the system" but didnt see any "pressure loss".
From this Im assuming all they did was pressurize the radiator and watched for a pressure drop. If they did this cold, most-likely such a pressure drop would not have been seen.
I havent seen any coolant in the exhaust...meaning I havent seen any steam.
Posted 05 August 2003 - 02:38 PM
Alas, your story makes sense.. although my experience has been the slower I go (fewer revs) the faster the engine will cool down. If I sit in a parking lot and let it idle for a few mins., the temps will start dropping to normal. Heats back up at speed, however.
The dealer did note this however: the radiator at the bottom was cooler than the radiator at the top. My local mech pointed out tho that the thermostat is at the bottom of the block, so it will close when it gets cooler, forcing the warmer coolant to the top.
Wierd, having the thermostat way from the temp sensor.. Id think you would want them pretty close together. But, guess it doesnt matter as long as everything works...
Guest_1 Lucky Texan_*
Posted 05 August 2003 - 04:28 PM
Perhaps there ARE larger bubbles collecting in the water pump BUT there is cavitation at high RPMs?
I also wonder if at some time tap water was used in your coolant? Maybe there are mineral deposits in the lower tubes blocking the flow of water? Might explain them being cooler. just a wag
Perhaps you have a complex condition or more than 1 cause.
Please let us know how this progresses.
1 Lucky Texan
Posted 05 August 2003 - 05:05 PM
Ahhh....yeah, therein is the question... the dealer did one test and determined its not a head gasket, and sd. the radiator was bad... after they pronounced it in good shape after they power-flushed it a few mos. ago.. so Im not real high on dealer diagnosis right now.
My local mech is incredibly honest and dilligent, but he doesnt have the sensors, testers and specific Suby knowledge that the dealer should have.
But, there are a limited number of ways that pressurized air can get into a cooling system, and none of them are cheap to resolve, that I know of... BUT, the coolant in there now (48 hrs. old at this point) still looks clean...
So Im on the verge of saying its worth $2K for a rebuild just to eliminate the engine as the source of overheating. This is the NASA approach.... <sigh>
Well, thanks all.. if I get any resolution, Ill let youall know.
Posted 05 August 2003 - 10:03 PM
if you are leaning towards a rebuilt, call ccr and see what the lead time is. if it is not too long, drive this one until it craps out, then change the motor...
Posted 06 August 2003 - 09:28 AM
Quite why it cools when idling, well, strange things happen when you trap liquids and gases in pressurised systems and start to pump them round. Expanding gas pockets might be forcing coolant backwards in relation to the normal flow direction.
You must check for hydrocarbons/CO2 in the coolant before condemning the entire engine !
Posted 06 August 2003 - 11:20 AM
Posted 06 August 2003 - 11:24 AM
Is there a DIY kit for exhaust gasses in the coolant? The dealer is gonna charge a fortune for this test, which arugably they should have done when it was in there, for a aksed to see if the HG was faulty.
Yesterday driving home I tinkered: if I vented the system while the engine was on, no gas escaped, although some coolant did go into the expansion tank.
When I turned the engine off and vented the pressure cap, quite a bit of gas burbled into the expansion tank.
At some point, this whole system reaches a stasis in which the temp. goes up, down, up, up, down, up, up, up, down, down, up, then settles to midway on the guage and pretty-well hangs there.
Guest_1 Lucky Texan_*
Posted 06 August 2003 - 11:40 AM
Yep, gasses and fluids under pressure, weird. You may even have a bad rad. cap on top of these issues.
1 Lucky Texan
Posted 06 August 2003 - 12:47 PM
Posted 06 August 2003 - 11:52 PM
If the cap can't hold at least 1.1 bar pressure the coolant will boil even without any leaking gaskets to help it along. Get a original Subaru replacement cap and try it out
Posted 07 August 2003 - 07:05 AM
Posted 07 August 2003 - 08:46 AM
Well,.. actually I didnt think of the radiator cap as culprit, but I replaced it anyway for another reason. I tried "burping" my rad with the conventional Suby cap. It worked fine once.. I could vent the pressure and replace the cap.... and ignoring the big ominous "this is a REALLY dumb thing to try to do" warning all over the cap and radiator.
Second time I tried it, there was too much pressure and I couldnt redirect the hot gasses away from me... so I ended up dropping the rad cap and watching Old Faithful burst forth in its murky brown splendor. Pretty impressive. Cooled the engine quickly too.
The orig. rad cap wasnt damaged, but with smarts finally cutting in, I got a pressure relieve cap for the rad and have been using that.
Anyway, the results have been the same, except Im saving on laundry bills. Oh, FYI: dry cleaners can't get radiator glop out of clothes....
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