2001 H6 3.0 OVERHEATING... Help Please!

[Dilbert]

Have a 2001 LL Bean 3.0 H6 OB with some overheating issues. Been fighting this for some time and at some enormously growing expense.

FIRST: Replaced radiator with new aftermarket because bottom half of radiator was "Cold" & "Must be 'Plugged' up"... Also changed cap and thermostat w/ new OE Subaru parts. Also ran pressure test for several hours; no drop in pressure, no leaks. Some improvement, but sporadically overheated, filling overflow, and overflow would not siphon back overnight. No OBD codes, no lights on dash.

SECOND: Replaced all three catalytic converters as they were shown to have "Too High" a temperature differential between front and back of the cat. Some improvement to performance but not any change to overheating.

SYMPTOMS: Primarily a problem when climbing hills at freeway legal speeds. Around town driving: no overheating, but every morning replace 1/2 to one cup of coolant; sometimes from overflow expansion tank with turkey baster, sometimes [about 50-50] have to add coolant to system [both radiator and overflow] Sometimes it's more like a quart low in radiator.

I'm in Sacramento, CA so no Mt. Everest climbs... mostly under 3500 ft elevation on major highways. Driving around trying to keep it under 1500 RPM is getting old. Most hill climbing is in the 2500-3000 RPM range.

Could the 2-stage OE muffler be a cause?

BTW Both fans operate correctly and currently about 185k miles

[idosubaru]

if you only do around town driving - is it still pushing fluid into the overflow or is that only happening at freeway speeds?

 

do you ever see bubbles in the overflow tank?

 

first step is get a mechanic that knows what they're doing or isn't hard up for cash. the catalytic converters were a complete waste of time on an overheating engine (and real cheap, right? ), there are other steps that should have been covered first. i'd rather not be negative but that's one of the dumbest things i've heard in a while...and from a mechanic with unbelievably more experience, training, and cert's than me? i'll be rehearsing this story with friends soon.

 

if the overheating characteristics are different now than they were - then the system may just need to be bled properly. you can search for "burping" or how to burp the system, etc for instructions. need to get the air out of the cooling system, which is tricky to do on newer engines. i'm not convinced this is the issue though, but certainly worth verifying.

 

it's starting to sound like headgasket issues - did the mechanic test for hydrocarbons in the coolant? that's what should be done given the coolant pushing into the overflow tank. (most auto parts stores sell a kit that does it with instructions so if you're using a baster to transfer fluid maybe you're up for giving this a try?).

 

if you go back to this same mechanic that doesn't know what he's doing, don't let him rely on a compression test - an engine can have failed headgaskets and still get a good compression reading, this is actually common with newer subaru engines.

 

if it is the headgasket then i'd start thinking about trying Subaru's coolant conditioner on this engine. i wouldn't normally recommend this for a non-EJ25 engine (you have the EZ30) but given the fact that this sounds like a similar failure mode for those i'd consider this an option before the expense of headgasket replacement. in some cases the conditioner can stop existing leaks where exhaust gases are pushing into the coolant - which it sounds like yours may be doing.

 

don't forget to find another mechanic.

[North to Alaska]

VW Very good post. well written.

Thanks. and my car doesn't even have a overheating problem..

 

our friends 3.0 had somewhat the same problem.

AAA 'the shop" anchorage, did a head gasket job, antifreeze change and added the subie water conditionor and a good air burping and it fixed that problem.

 

I also use the subie conditionor in our fishing lodges water cooled kobota power plants (2)(12Kw)

The kobota dealer said to:

"use the subie stuff in the coolant.

And said it doesn't have anything to do with their head gaskets."

Edited May 26, 2011 by North to Alaska