I thought it might be useful to have a place to note problems strongly suspected to be caused by the subaru coolant additive, a.k.a Holt's RadWeld.

 

I know what the goop looks like because I'm trying it out in my H6 (external head gasket coolant weep), but the problem was on my wife's 2005 Forester, which I assume had the magic goo added by the dealer after it had its head gaskets replaced (external oil leak).

 

Anyway, on a trip the rad was not holding pressure, too much coolant was being sent to the overflow reservoir, and it was not sucking coolant back up from the overflow.

Problem was the cap.

 

Checked the cap under magnification, looks like some of the magic goo collected on the metal plate that seals under pressure and allows the coolant to be sucked back in.

I know some people don't like the stuff but I'm not sure. I've been using it in all my soobs for many years, so far I haven't seen any issues from it. There was a TSB or note on Endwrech about the rad caps, something about making sure no debris is between the rubber part and the metal underneath, I think it talked about using basically a toothbrush to make sure it is clean under there.

I haven't had any issues with it and have used it on the 2000+ cars where recommended.

 

I recently bought a car that the previous owner attempted a bottle of HG repair several times. I had to blow out the heater core to get heat. but fortuantley everything else is OK.

 

How many miles on your 03 LLBean? I have an O2 LLBean with 104 and so far all is OK.

 

My beaner has a bit over 193k, recently showed some damp/wet green spooge at the head gasket, but the edges of the head gaskets have been greenish from coolant for probably 40k miles.

 

The problem with magic additives is when they don't work, some goober always says 'well then maybe 4 will work!'.

I am sorry I'm not up to speed on this. Has it indeed been established that the Subaru additive is RadWeld?

Yes. It even says Holts right on the bottle. Look at this pic scroll down and there's a side by side comparison. It says Holts on the Subaru bottle.

Yep, mine from the dealer said 'Holt's' right on the side...