Index Home About Blog
From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Heater Core Update
Message-ID: <>
Date: Mon, 11 Aug 2003 23:12:50 -0400

On Mon, 11 Aug 2003 19:14:48 GMT, "DeLores Wilson" <> wrote:

>Will do.  I also read them Neon John's suggestions of things to check out.

One other thing to make sure of.  Have them check the clamps and hoses going
to the heater core.

About a year after I changed the core in mine I started getting steam out the
vents and the smell of antifreeze again.  I just knew that the core was
boogered up again.  Several weeks later I got around to checking the hose
clamps.  They had relaxed on the new hose.  A tiny jet of coolant was
squirting from between the hose and heater nipple, right through the foam
firewall seal and into the heater air box.  I tightened that clamp and the
problem went away.

One other thought.  If that drop of coolant really did come from the heater
core, you might try some anti-leak before paying the big bux.  Oh, maybe 8
years ago the core in my 68 Fury started leaking. I saw another dashboard
removal looming so I tried the Bars-leak.  I didn't really want to put that
stuff in the coolant because the sodium silicate in the stuff is hard on pump
seals.  What I did was rig up a little pump loop between a small pump (one of
those el-cheapo drill motor operated pumps such as Harbor Freight sells) and
the core itself.  The pump circulated the solution in a loop.  I used a heat
gun to heat the core enough to activate the stuff.  After a couple of hours I
flushed the heater very well with clean water and connected it back to the
coolant system.  Hasn't leaked a drop since.

This stuff contains a mix of metal particles and sodium silicate ("water
glass")  The metal particles agglomerate at the hole and mostly block the
flow.  Water Glass reacts with CO2 in the air to make a glass hard substance
that cements the metal particles in place, totally blocking the leak.  As long
as there's no flexure at the point of the leak the seal should be permanent.

I wouldn't expect the dealership to be able to set up such a system but an
independent or a friend might be able to.  A radiator flushing machine would
be ideal for the task.

Even if the heater core is leaking a little it has nothing to do with the
overheating.  I'm betting either glazed belts or a fan clutch gone south.
Unless you've really abused the cooling system by adding dirty water or
something like that, the rig is probably too new to have scale problems.


From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Heater Core Update
Message-ID: <>
Date: Thu, 14 Aug 2003 12:13:24 -0400

On Wed, 13 Aug 2003 22:13:11 GMT, wrote:

>bill horne wrote:
>> --------------------------------------
>> NOTICE: Two sealant pellets GMSPO part no. 3634621 must be added to the
>> radiator whenever the coolant system is drained and refilled with fresh
>> coolant. Failure to use the correct pellets may result in premature
>> water pump leakage.
>> --------------------------------------
> Neon John mentioned in his  post that some sealants could promote premature seal
>deterioration. Your quote confirms what he said.
>Bottom line is that one manufacturer recommends using the pellets whenever the coolant
>is replaced so the pellets must have some efficacy.

Just so there's no confusion, the GM magic pellet and BarsLeak and similar ilk
are quite different.  I've never bothered to find out what is in the magic
pellet but it can't be water glass.  Water glass is hard on the water pump
because when the pump is idle, a little can seep through the shaft seal.  This
reacts with CO2 and forms a glass-like substance that is very abrasive.  Not
good on the carbon/ceramic seal.  In fact, sufficient leakage can momentarily
stick the two together.

There's a joke going around that GM uses those pellets to make up for an
inability to cast non-porous blocks nor do precision machining.  I'm sure the
real reason isn't that bad :-)  I doubt that the gold pellet would seal a
major leak like a heater core perforation.  It really does just address
seepers plus adding a water chemistry package - anti-corrosion, etc.


Index Home About Blog