'01 H6: Inadequate cooling

[jonathan909]

Just got back from another little boat-hauling road trip, this time over the Rockies and into the British Columbia interior, where it's pretty damn hot.  Two years ago the town of Lytton burned down after the temperature exceeded the highest ever recorded in Las Vegas.

My problem is that in 30+ heat I was barely able to hold the temp gauge's 9-o'clock norm.  Any extra load - climbing a hill or turning on the AC - would cause the temp to climb, forcing me to slow down, turn off the AC, even turn on the heater in an effort to keep it from going past the 10-o'clock mark.  That I can tweak it on the fly like this suggests that it's a marginal problem, and in the past (e.g. with my old 318 Dakota) the answer was a new rad.

1. Is there any reason not to take the same approach this time?

2. Of the rads available from Rock (in ascending order of price):

CSF, Ultra-Power, TYC, FVP, UAC, Koyorad, Agility, GPD, Denso

are there any particularly good or particularly bad?

 

[idosubaru]

16 hours ago, jonathan909 said:

Just got back from another little boat-hauling road trip, this time over the Rockies and into the British Columbia interior, where it's pretty damn hot.  Two years ago the town of Lytton burned down after the temperature exceeded the highest ever recorded in Las Vegas.

My problem is that in 30+ heat I was barely able to hold the temp gauge's 9-o'clock norm.  Any extra load - climbing a hill or turning on the AC - would cause the temp to climb, forcing me to slow down, turn off the AC, even turn on the heater in an effort to keep it from going past the 10-o'clock mark.  That I can tweak it on the fly like this suggests that it's a marginal problem, and in the past (e.g. with my old 318 Dakota) the answer was a new rad.

1. Is there any reason not to take the same approach this time?

2. Of the rads available from Rock (in ascending order of price):

CSF, Ultra-Power, TYC, FVP, UAC, Koyorad, Agility, GPD, Denso

are there any particularly good or particularly bad?

 

Doubt there’s enough scale to differentiate beyond anecdotes. Ive used a few CSF radiators, maybe 5-10.  haven’t kept track of brands but end up with CSF most often by far, including at least one H6. they’ve fit right and worked fine. Second most would be Koyo I think. Also worked fine.

I think GD said Aftermarkets are reasonable (he doesn’t say that often), but he’s seen the radiator cap not seal properly due to the internal neck sealing depth/surface.

One could check cap sealing while it’s still under warranty.

I’ve had the same issue towing other Subarus or large boats with an H6. Same thing. Fine until its steep grade, 90+ degrees. 

ensuring condenser fins are clean and straight will improve airflow to the rad. there are fin straightening tools if needed. 

A dedicated AT cooler would incidentally expand cooling capacity. That’s what I thought of doing but never did. 

[1 Lucky Texan]

our moderately loaded (3 adults, a little luggage) '03 H6 would begin to overheat when we were going up grades in Nevada heat - 114-117 degrees indicated by the car's therm.

I just backed off on the speed. wish I had experimented with downshifting to 3rd.

I guess it's just near the limit.

[Numbchux]

My '04 VDC started doing that a couple years ago (~250k miles), and eventually got bad enough to require significant change in driving style to keep it from getting dangerously hot. I used a Spectra aftermarket radiator when I repaired the crash damage it had when I bought it (at 133k miles).

 

A serious cooling system flush solved it. Put a flush chemical in it and drove it for a few days, drained, filled with coolant and flush, drove for a few days, then drained, removed the radiator so that it could be intensely flushed inside and out, and the condenser could be sprayed out from the engine bay side. Then disconnected and flushed the heater core, and then engine. Temperatures stay perfect, now (I put the 100+k mile aftermarket thermostat right back in with a new gasket).

[jonathan909]

1 hour ago, idosubaru said:

I’ve had the same issue towing other Subarus or large boats with an H6. Same thing. Fine until its steep grade, 90+ degrees.

Whoa - that's a steep grade alright!  What kind of tires do you use with that?

[jonathan909]

Wot, crickets?  I thought that was a good one.  Tough room.

[jonathan909]

2 hours ago, Numbchux said:

A serious cooling system flush solved it. Put a flush chemical in it and drove it for a few days, drained, filled with coolant and flush, drove for a few days, then drained, removed the radiator so that it could be intensely flushed inside and out, and the condenser could be sprayed out from the engine bay side. Then disconnected and flushed the heater core, and then engine. Temperatures stay perfect, now (I put the 100+k mile aftermarket thermostat right back in with a new gasket).

That's a lot of fuss for something that costs a hundred bucks to replace (here I am on the other side of that argument for a change), but maybe worth giving a shot.

Any preferred product for flushing - or any to avoid?

[Numbchux]

1 hour ago, jonathan909 said:

That's a lot of fuss for something that costs a hundred bucks to replace (here I am on the other side of that argument for a change), but maybe worth giving a shot.

Any preferred product for flushing - or any to avoid?

Maybe just throwing a new radiator at it would have done it. But I feel much better having flushed the engine and heater core, too. Circulation through the heater core is crucial for thermostat operation.

I don't think anything is bad, per se. I used Gunk, and we use Wynn's at the dealership where I work.

[idosubaru]

20 hours ago, jonathan909 said:

That's a lot of fuss for something that costs a hundred bucks to replace

His implied point is to flush the entire cooling system. 

I use Georgia Tech gecko adhesion technology on my tires for those 90 degree grades. Now, off to keep skis and tubes from falling out of the boat….