Several days ago I wrote:
A (the?) freeze plug on the right hand side of my TR-250's block (hidden
behind the exhaust manifold) is leaking badly and needs to be replaced.
Just following up here. I got lots of good input for which I am very
grateful. Many of the replies appeared to be sent just to me and not to one
list or the other, so I thought it would be worthwhile to post a summary of
the responses I received. In no particular order:
* Don't look cross-eyed at the water return pipe unless you have a
replacement handy. It is almost certainly corroded and will leak.
* Use a non-hardening gasket compound like Permatex #2 to seal the new
plugs to the block.
* Bob Lang reported that Moss is apparently selling some metric plugs
which don't fit. Bob now buys his plugs from NAPA.
* Bob also suggested trying a bottle of "Bar's Leaks" or similar. I
figured I could afford $3 for the experiment. Unfortunately, it
failed. The hole in my freeze plug appears to be a gusher. All the
coolant just sprayed out the hole.
* There are three on one side (the right, I think) and two on the other.
Might as well replace 'em all. There are others on the front which
require that you pull the water pump housing.
* Obviously, you'll have to replace what you break during disassembly.
You should be prepared to replace studs, bolts, nuts, the
aforementioned water return pipe (and its fittings) in addition to the
plugs themselves and the manifold gasket. Bob says to have at least
one spare of everything.
* It's not clear if I will be able to just tip the exhaust manifold out
of the way or if I'll have to disconnect it from the exhaust pipe. I
saw responses both ways. The exhaust system doesn't have too many
miles on it (the Walker label hasn't yet burned off the muffler), so
hopefully I'll be able to disconnect the two if necessary.
* William Hooper added a particular note of caution about the nuts and
studs on the heads: "Go slow with the nuts on the head: wire brush off
as much corrosion as possible, use lots of penetrating oil, & go slow.
Break a stud off the head, & you will be getting into new, difficult
problems."
* Aaron from Maine recommended decrudding the coolant pipe which runs
through the intake manifold while that's off.
* Dave Herbert recommended using a coolant pump to pressurize and test
the cooling system after replacing the plugs but before bolting the
manifolds back on. I did a little checking around. Various models
are available on the net for between $40 and $100.
After all the responses I received, I've reached a tentative conclusion
about how I got into this particular fix. Last summer I decided I needed to
flush and fill the cooling system. I had just replaced the water pump and
not long before that had replaced the rad hoses and the big metal pipe (not
the wimpy water return pipe). Even though a peek inside the radiator showed
it looked fine, I knew that it had been years and years since it was last
flushed. I did the whole flush and fill thing, in fact I flushed it 'til
the cows came home. I suspect that the flush chemicals and the overall
process chewed away at the already badly corroded freeze plug(s). Add to
that a proper new radiator cap which probably boosted the pressure in the
system a bit, and the one freeze plug let go.
I have one other question. Are there small enough passages in the cooling
system that it's conceivable I have a blockage somewhere which might have
boosted the pressure in one part of the system? Is there a diagram online
of the cooling water flow through a Triumph 6-cylinder block? I'll check my
service manuals before I tackle this. I have a feeling I've seen something
before.
Thanks,
Skip Montanaro
'68 TR250 - CD4212L
skip@pobox.com
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