Hi, I have a ’95 Blazer with a 4.3L Vortec V6. The engine has
developed an internal coolant leak. No external leaks are visible. A
considerable amount of white smoke comes out of the exhaust. The
coolant level drops and there appears to be coolant dripping out where
the right exhaust manifold mates to the Y-pipe. I pulled the right
side plugs. The #6 plug appeared to have a little more buildup on it
but all appeared dry. I cranked the engine over, but nothing came out
of the plugholes. The question I have is, could this leak be from the
lower intake manifold gasket or a head gasket problem or worse? Thanks!

<zwickl2 (AT) frontiernet (DOT) net> wrote

Hi, I have a ’95 Blazer with a 4.3L Vortec V6. The engine has
developed an internal coolant leak. No external leaks are visible. A
considerable amount of white smoke comes out of the exhaust. The
coolant level drops and there appears to be coolant dripping out where
the right exhaust manifold mates to the Y-pipe. I pulled the right
side plugs. The #6 plug appeared to have a little more buildup on it
but all appeared dry. I cranked the engine over, but nothing came out
of the plugholes. The question I have is, could this leak be from the
lower intake manifold gasket or a head gasket problem or worse? Thanks!


Does the heater blow hot air?
Does the coolant look dirty or oily?

Hot air blowing from the heater and clean coolant
would point towards an intake gasket leak.

Cold/slightly warm air blowing from the heater and
dirty/oily coolant would point toward a head gasket issue.

Some white smoke could be from a badly leaking intake gasket.

Lots of white smoke would indicate a blown head gasket
or even possibly a burned piston.

I would do a compression/leakdown test of all cylinders.
Even compression across all cylinders would eliminate
a head gasket/burned piston.

Regards,
JR

<zwickl2 (AT) frontiernet (DOT) net> wrote

Hi, I have a ’95 Blazer with a 4.3L Vortec V6. The engine has
developed an internal coolant leak. No external leaks are visible. A
considerable amount of white smoke comes out of the exhaust. The
coolant level drops and there appears to be coolant dripping out where
the right exhaust manifold mates to the Y-pipe. I pulled the right
side plugs. The #6 plug appeared to have a little more buildup on it
but all appeared dry. I cranked the engine over, but nothing came out
of the plugholes. The question I have is, could this leak be from the
lower intake manifold gasket or a head gasket problem or worse? Thanks!

Does the heater blow hot air?
Does the coolant look dirty or oily?
How much smoke is "considerable"?

If the heater is blowing hot air, the coolant is clean, and the smoke is
not too bad,
it would indicate to me the intake gasket is leaking badly.

If the heater is blowing cold or slightly warm air, the coolant is
dirty/oily, and the
engine smokes badly, it would indicate a blown head gasket or even a burned
piston.

I would do a compression/leakdown test.

Even compression across all cylinders would point toward an intake gasket.

Uneven compression across the cylinders would indicate a blown head gasket
or piston
problem.

Please let us know what you find, I'm curious.

Regards,
JR

Well, I finally got around to replacing the upper and lower intake
manifold gaskets. The right rear area where the lower manifold mates
to the head appeared to be damp along with the #6 intake runner, but
nothing conclusive. The intake manifold gasket appeared to be
deteriorated but not through to the water passage. I finished the job
and started it up. The truck continued to smoke for 20 minutes so I
thought that I had not solved the problem. I drove it and after about
1-2 miles, it stopped smoking and ran fine. No problems after about
100 miles and the coolant level is steady.