Cooling system "conditioner" for 2000 Forester

[Lono]

Like many, it appears, our 2000 Forester with 70k miles has a very small
leak from a head gasket design failure. The symptom isn't a visible
reduction in coolant, or oil in the coolant, but a smell after shutdown.
Nothing new.

According to the dealer, one solution is a $1200 repair. Another
solution is the little blue bottle of conditioner marked HOLTS sold for
under $3 by the dealer, added every once in a while. It's obviously a
sealant or leak plugger. The "while" is not defined...

Any advice other than those two options?

[VanguardLH]

I don't have an engine with the gasket problem, but if I did then I
figure the additive would go in with each coolant flush.

By the way, from what I remember reading about their "sealer", it isn't
just a plug-type sealant but a heat-activated plug sealer. It's to plug
leaks into the cylinder where is the higher heat.

One reader here in the past stated that the Subaru conditioner is
actually Holts' Radweld. I didn't have a bottle to inspect.
http://www.holtsauto.com/products/group/repair-and-maintenance/cooling-repair-systems#holts-radweld
From a pic of Subaru's product (http://tinyurl.com/bqy7lfg), "Holts" is
embossed at the bottom of the plastic bottle so it's a dead giveaway.

The claim is that this stuff "dissolves in the coolant and remains a
liquid untill it is exposed to air and high temperature." The important
word here is "and". Just exposure to air would mean it would plug any
leak, like to the outside or even in the radiator or heater core. While
it gets hot along with the coolant, that isn't hot enough. It takes the
high temperature of the cylinder to activate the stuff so it seals
against coolant leaks into the cylinder, not elsewhere.

They don't describe how it works. I found its MSDS at:
http://www.kramp.com/pdf/en_US/holts_radweld.pdf

Alas, the MSDS (http://en.wikipedia.org/wiki/Msds) only has to list
components considered hazardous so there can be ingredients not listed
in the MSDS that are in the product. From the MSDS, disodium
tetraborate is borax (http://en.wikipedia.org/wiki/Borax) which is a
cleaner (removes oxides). Phosphoric acid is also a cleaner and rust
converter (http://en.wikipedia.org/wiki/Phosphoric_acid).
Triethanolamine is probably an emulsifier to meld the product into the
ethylene glycol (coolant) and used as a regenerator or booster; i.e.,
this is the "conditioner" portion of the product.

Ingredient list on the bottle:
http://www.scoobyenthusiast.com/photos/user-albums/image/subaru-cooling-system-conditioner-ingredients#

Ingredients listed on the bottle don't seem to match on Holts Radweld
MSDS: see http://tinyurl.com/celt2or. The resin is the air+heat
activated component. The linseed meal is a fibrilated fiber
(particulate) suspended in the additive (and then in the coolant to
which the additive is added) that is used to fill gaps too large for the
resin to handle alone (http://tinyurl.com/87c9b3f, "BACKGROUND OF THE
INVENTION" section). The resin fills the cracks, the meal fills the
gaps.

In the past, I found the following Subaru-sourced info on their coolant
sealer, er, "conditioner", er, sealer+conditioner (SOA 635071):

Subaru "Endwrench" - Cooling System Conditioner
Whenever the coolant is changed, you must add Genuine Subaru Cooling
System Conditioner, (P/N SOA635071). ItοΏ½s been tested and approved for
Subaru aluminum engines and radiators. Do not use aftermarket coolant
reinforcement agents, sealers and/or flushing agents as those
chemicals could corrode aluminum parts, or cause clogging. Genuine
Subaru Cooling System Conditioner improves the efficiency of the
cooling system and includes anticorrosive properties. When used as
directed, it remains suspended in the radiator until the engine is
started and thermostat fully opens. Once the conditioner begins to
circulate throughout the cooling system, it is attracted to any
suspected leakage area in the vehicleοΏ½s cooling system. The heat
generated by the engine acts as an activation agent and hardens the
cooling system conditioner to help seal the area. Subaru of America,
Inc. has determined that this product is safe for use in all Subaru
vehicles."

So, yep, looks like you add it with every coolant flush. If you're
going to add it, do so to new coolant; i.e., do a flush, put in the
additive, and add the coolant. Don't waste it on old or reused coolant.

Below is some other Subaru info I found on which engines need their
special "conditioner" (they don't like calling it a sealer):

For phase 1 engines, the leakage is internal hence destructive.
Hydrocarbons show up in the coolant (detectable only with specialized
equipment) and may appear as sludge in the overflow tank. Bubbles are
seen in the coolant immediately after starting the car. Overheating
can be erratic but most often experienced on slowing down or stopping
after running the car at highway speeds for awhile. Owners have
thrown lots of money at trying to resolve various symptoms, like
replacing thermostats, coolant flushes, new water pumps or radiators.
If overheating occurs too often or is severe, head warpage occurs and
requires engine replacement.

Whether you have the destructive internal leak or non-critical
external leak depends if you have a phase 1 or 2 engine.

Phase 1: dual overhead cam
96-99 Legacy Outback or GT
98 Forester or Impreza RS

Phase 2: single overhead cam
2000+ non-turbo Legacy & Outback
00-04 Legacy GT
1999+ Forester or Impreza 2.5

You sure you need the Subie conditioner? Doesn't your vehicle qualify
as having a phase 2 engine? Phase 2 engines have an external leak so
you don't need their special sealer, er, conditioner (but it probably
works as well as other stop-leak additives). When you start the engine,
the coolant that leaked externally onto the engine is too cold for you
to smell, and when you start driving then you won't be smelling it.
It's when the engine has gotten hot and you park the car when you smell
the external leak from the coolant on the hot engine. For an internal
leak (phase 1 engine) of coolant into the cylinder, you'd see white
smoke out the exhaust and that's where you'd smell the coolant. Unless
you had a rear hatch window/door open when you stopped, I'm not sure
you're going to smell coolant coming out your tail pipe. Maybe you'd
smell it when starting up and sitting there while the engine warmed up.

Whether it's an internal (phase 1 engine) or external (phase 2 engine),
the Subaru rebranded Holts stuff probably works just as well for either
engine type and leak direction; however, there are probably cheaper
alternatives for an external leak. The real solution is to replace the
defective gasket but, as you see, that's a pricey choice. Since you're
probably only replacing the coolant (flush and replace) about every 5
years, the per-year cost difference for getting the more expensive
Subaru conditioner probably doesn't amount to much. Personally I don't
believe the claimed 11-year/120Kmile life cycle of Subaru's special
coolant mix (http://www.cars101.com/subaru/subaru_maintenance.html).
Depending on environmental conditions, I replace at 3-5 year intervals.
I'd get nervous going longer than 5 years. The hygrometer you use to
measure to the density of ethylene glycol doesn't measure the other
components (anti-rust, cleaner, oxidant, surfactant).