LA 318 cooling prob has me fretting

1986 LA roller cam 318 in an M-body, 85K, mysteriously started sucking
air (or exhaust gas) into the cooling system, causing odd overheating
symptoms. Off came the whole top end, with judicious inspection of
the heads as well as deck and head surface flatness. All looked well,
and the valves were in pristine shape. After complete cleanup, new
Fel-Pro gasket set (along with the "one size fits all LAs" head gasket
that robs you of 5 lbs of compression!), figuring it was a pinhole
leak in one of the head gaskets. Back together, with the freshly
kitted carb, new RN12YCs, new wires/cap/rotor, new O2 sensor and
meticulous reassembly, the old LA ran SO smoothly and quietly it was
eerie. However, here comes the bubbles...again! Prior to the top end
job, I had fed 125 lb. air to each cylinder, and never did get
positive sighting of bubbles in the top tank of the radiator. But, a
firing cylinder under load, even in a low compression engine like
this, produces a lot more than 125 lbs. on the cylinder walls.

I can only think of two possibilities...lip seal in the water pump is
sucking in air, or...there's a pinhole in one of the cylinder walls
that's allowing exhaust gas to pass, but not water to pass the other
way. While glaze busting the cylinders, there WAS an odd little rust
spot in #5 that I attributed to water getting in there during head
removal (don't you LOVE they way they hid those drain plugs behind the
new style motor mounts????), but it went away with a single pass of
the hone, and nothing looked unusual. However, this engine, while in
great condition overall (.0002-3 taper in all cyls...barely a ring
mark to be seen) the original owner (the know-it-all father-in-law)
didn't seem to believe that you needed to change antifreeze regularly.
Thus, the jackets were FULL of rust flakes, necessitating me taking a
pressure washer nozzle down into the block to clean it up. After the
pressure washer treatment, the walls of the water jackets were grey
iron with ocassional dark rust spots here and there. However, if by
doing this, I knocked all the rust loose, the problem should've gotten
worse, and it didn't. Actually, it improved...slightly...but it is
still there.

Prior to this, this engine would NEVER get more than 5° above
thermostat in any condition except pulling a grade when 110° out with
the AC on. Now, it gets up to 210° just putting around town at 45
MPH.

Anyone heard of any bad block castings on this vintage LA engine?
Also, anyone had a water pump do exactly what this may be doing? No
bearing noise, and the weep hole is clean, but it's a two year old
"rebuild" (the original blew the seal right out the nose on a trip to
Vegas on the hottest day of the year).

The car, an '86 M-body 5th, is a cream puff, and I've grown to love
it, even with its various faults. Strengths: comfy "rich Corinthean
leather" seating all around; low noise level; excellent handling;
excellent AC; straightforward, honest design, no engineering
"gotchas," and it has Lee Iacocca in the trunk under the spare cover.
(Ricardo Montalban is a no-show.) Weaknesses: Choppy ride at times;
A-904 TF's lockup converter locks up at 36 MPH in 3rd gear...no matter
WHAT the load...no part throttle unlock...have to downshift to second
to knock it off; the usual headliner replacement (normal in any car
this old); jiggly front sheet metal on rough roads; rather ungainly
styling; and the standard MoPar feature...HARD to work on in places,
something I think that's been a MoPar standard since the '60s. You
need every wiggle and U-joint extension you may have in your
rollaround, but if you're smart, everything comes apart fine.

Hate to trash this car for a porous cylinder wall. My wife loves it,
too (it was her mom's when new) and it hasn't even hit 100K yet, and
the paint and interior are still quite nice and draw compliments
wherever we go.

Any opinions?

Caveat: If you have an old engine with low mileage where the original
owner ran long oil change intervals with mediocre oil, and you see
crusty sludge on the rockers (or wherever,) do yourself a
favor....strip the top end, clean it out BEFORE switching to
synthetic. I didn't, thinking the syn would sort of erode the
carbonized oil and slowly send it to the filter. I got away with it,
but after my clean up after dear Dad-In-Law, I'd never chance it
again. The amount of crap loosened up and laying in the pan was a bit
scary. Oddly enough, the pickup screen was clean, but every oil
change, that filter (Fram Double Guard) was HEAVY. I changed out the
oil pump just to feel safe, and later disassembly of the original
proved me right...there was a LOT of abrasive wear in it.

 

To much for me to read ths early. Just curious..was the vehicle loosen
coolant before repairs? And did you get the intake manifold gaskets on
properly??? they will go on backwards and the only problem you will get is
an overheat condition if you close off the coolant passage from the head to
the intake.

Glenn Beasley
Chrysler Tech

 

Since it was doing it before teardown I would look at the radiator. With
that much rust have you checked the radiator flow, Maybe the fan clutch.
Did you have the heads maged or the valves done ??? I have some LA intake
gaskets in my hand don't see any difference in the water passages Take it
to the local radiator shop & have them do a block check. or if you have a
friendly smog man he could check for exhaust gases with his analizer

 

Did you check the timing case? I had a 273. After 200,000 miles, some
pin holes developed in the casting right behind where the water pump
impeller sits. I didn't notice any bubbles, but coolant was getting
into the oil.

-KM

 

There are those here who will adamantly disagree about synthetic
dissolving and breaking loose deposits, but I agree with you that it
definitely does and that those that suddenly switched over without a
problem were just lucky.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

No, but gas bubbles would be escaping into the reserve tank after
shutdown.

Of course. The problem existed BEFORE the teardown.

Only an idiot would install LA intake gaskets backward. I'm not one
of those.

 

Backflushed core, got some particulate rust out, now flows fine,
minimal deposits.

Negative...works as new.

I personally magnefluxed those heads...no cracks anywhere. To
confirm, I took them to the local grinder shop and had them Zyglow
them....same thing, no cracks.

One this particular application, both sides are the same. However on
many earlier LAs (and As) the BACK water passage is active and has a
metering hole. If the numbnuts installed the gaskets backward, there
will be no flow to the thermostat.

Checking for exhaust gases today with a NAPA tester I just picked up.
I'm fearful that there are these, because after running a couple of
days, the water/inhibitor takes on a "rainbow sheen" when exposed to
light. However, I've been told that also could be water pump bearing
grease being sucked into the system from the bearing, presaging a pump
failure. I'm putting a new Cardone pump on after checking for exhaust
gas presence. If there ARE exhaust gases, I'm afriad the block
porosity problem is real.

 

Update: Exhaust gas presence negative. Water pump goes on as soon as
it gets here, stay tuned.

Meanwhile, three wrenches I know have warned me about shops using
"cheapie" rebuilt pumps from schlock vendors like Poop Boys or Auto
Bone, and they ALWAYS have seal and/or bearing failure within two
years.

Looks like this might be the case, since the car had a "rebuilt" pump
installed when on a trip to Vegas. The original blew the lip seal
right out the nose on that one.

 

When you remove the pump, inspect the condition of the pump housing in
timing case. Please see my earlier post.

-KM

 

Will do. I've been told it could be possible that the front cover
suffered corrosion damage due to poor cooling system maintenance early
in its life, and if the perforation is near the center of the hub,
crankcase blowby could be getting sucked into the water stream.
However, one would think that if this were so, the hole would be big
enough to leak water into the pan, and I'm not seeing that.

More later, and thanks.

 

there is a tool that uses air power to pull a vacuum to purge air from a
cooling systems so it can be charged with coolant and eliminate air in system
i have on occasion used mine to find a leak in the radiator that shows up under
a vac condition and not pressure and can allow air into radiator and the cooling
system under cool down cycles.
mighty vac makes one and so does airlift .as well as bluepoint and mactools
there is also a chemical check kit that can be had from the better parts stores
that can tell you if there is coolant in oil and oil in coolant and if head
gaskets are indeed leaking.come to think of it my mac guy keeps the kits on his
truck now
you should have had the heads checked for cracks since they were off
does the pump impellar spin in the correct direction ?i have seen a few put on

 

Already did that. When I pull a 15" Hg vacuum on the cooling system
(tested today) I get air incoming. I just used a standard
refrigeration vacuum pump and an isolation vessel to keep water out of
the pump intake. Worked like a charm. I had to change the oil in the
pump anyway, so I gave it a go, and it works better than a MiteyVac or
any hand held device like that.

That's what this is doing. Negative for water/inhibitor in oil, but
I'm seeing a VERY slight "rainbow sheen" in the water/inhibitor that's
not normal, and usually is either grease or oil. I'm thinking a
micro-sized pore in the front cover is allowing crankcase gas to get
sucked through, but it's not big enough to pass water directly into
the timing chain area. I'm still stuck, though, on the idea that the
lip seal in the water pump isn't holding against a partial vacuum.
Since a new pump is on the way, I'm not going to repeat the vacuum
test and spritz heavy oil into the nose of the pump, but that'd prove
it.

Odd, in that I took the car out today, the partial heating up started,
and then BOOM...went back to 195° and stayed there! It never heated
up again on the rest of the trip, and I had the AC on as well. A 318
in these cars never gets more than a few degrees above thermostat
temperature in normal conditions, and I've never seen it get above
around 205° on the road, ever, even in hot summer desert trips. A
195° 'stat isn't even fully open until 215°.

Got a NAPA combustion gas test kit. Negative for combustion gases in
the water.

I Magnafluxed them myself in all the usual suspect places, with
negative results. Not trusting my old Magnefluxing ability, I had
them Zyglo'd at the local grinder shop...negative also. I also pulled
the valves while cleaning up the heads and looked above the exhaust
seats...nothing. No sign of incursion of antifreeze or rust anywhere
on them, and all 16 valves looked pristine. Those induction hardened
exhaust valves on Chryslers are TOUGH! Same goes for the chrome
plated stems. I've done a lot of various engines, and never seen one
with 85K with so little guide taper. Makes GM stuff look like the
junk that it really is.

The factory pump failed on a 113° day after shutting the engine off in
the desert on the way to Vegas...blew the lip seal right out the nose
of the casting. After a flatback ride to Vegas, a Sinclair station
installed a "rebuilt" pump, and it functioned perfectly for almost two
years, then this cropped up.

I'm also suspecting the front cover, because "Mr. Know-It-All" father
in law is notorious for BSing about car maintenance, and I don't think
he ever changed the antifreeze in at least 10 years, although the car
only got 28K miles in 15 years. An acetic condition in the cooling
system would attack aluminum parts first, so I think the other
poster's mention of his 273 with a porous front cover is quite valid.
Won't know until I pull the pump. Meanwhile, the wife's taking it to
work and reporting back tonight about temp issues.

I sure hope it isn't anything else. This car runs like a dream
(although with the usual low power) and gets pretty good economy...17
around town, up to 28 on the road. It was obvious when the O2 sensor
crapped out; I didn't even have to test it. The system went open loop
and around town mileage went down to 12-13 along with a fluffy black
exhaust pipe. When the feedback system's working right, though,
there's a little "surge" when under light power in lockup third gear.

Another thing: The AIS passages in the intake manifolds were
partially plugged with carbon, probably from running too rich due to a
failed O2 sensor. Now that everything's cleaned up (and I unstuck the
vanes in the air pump) the exhaust is medium gray and the mileage is
back up again.

People generally don't hold M-bodies like this in very high regard,
but I must tell you...it's a good, honest car that does everything
pretty well and some things really well. Just don't expect to go very
fast with 120 BHP!

 

I've read down this far, and it looks like you do NOT have a leak
between the cooling system and combustion chambers. Good news. If I read
right, what you DO have is an overheating condition with no evidence of
coolant being lost, correct?

That being the case, I'd look into a couple of areas. First- water pump
(but it sounds like you're onto that alread). Second would be the
radiator- you said it had been neglected, so have it rodded out (or
replace it). Third is the fan clutch. Yes, it may pass the "spin it by
hand and see if it stops" test, but still be inadequate. Been there,
done that. I would definitely invest in a new fan clutch on general
principle in a car this old (nevermind the miles- it may have lost some
of its fluid out the shaft seal or the thermostat seal in the front.)

If there IS coolant loss and I just missed the description, then those
who have pointed to the timing case are making a very good suggestion.
That, along with the fact that coolant flows through the intake
manifold, are the two big weaknesses of the LA cooling system compared
to the superior B/RB cooling system in my opinion. Mixing oil and water
in a B/RB v8 is a virtual impossibility (barring a blown head gasket or
cracked block).

 

That's it, Steve. Air/gas is being drawn or injected into the system
from somewhere.

A new Cardone rebuild showed up in UPS today, but won't get to it
until at least tomorrow.

The old "flow test" routine proved OK (especially considering it's a
single row core) but I think I'm going to pull the tanks off of it
anyway and give it a rod job, just to be on the safe side. Geez, I
haven't rodded a radiator in what...15 years???

I'm 99.9999% confident in the fan clutch. Starts up, fan at full
speed, once the silicone works its way to the outer edge of the body,
fan slows down. However, once hot water hits the core, and the AC is
on, and the bimetal coil heats up, I do get full fan again. I'll keep
that as the absolute last thing to replace.

I'm really thinking one of two things are going to wind up being the
resolution: 1.) corroded, "spongy" aluminum in the front cover,
causing crankcase gas to be drawn in around the back of the impeller,
or 2.) the lip seal on the front of the pump either got some crud in
it or failed completely. A NAPA combustion gas test again proved
negative, and I again see a slight oil or grease sheen on top of the
water. That would indicate to me that it's sucking crankcase vapors
(and oil mist) through a pinhole in the front cover. You'd figure
that a hole that big would also leak water into the timing chain
compartment, but so far, there's nothing to indicate any moisture at
all in there. I've seen that before on '60s Buicks, and you usually
get steam coming out of the breather if you pull the PCV out.

Still not resolved. However, the engine (before it starts heating up,
anyway) runs easily as well as when it was new...no flat spots, EFC
computer seems to be working perfectly, idle is glassy smooth, exhaust
is a nice, clean light gray, and fuel economy seems back toward
excellent, although I still won't take it out on the road until this
cooling mess is cleared. Just driving around out and about, it turned
in 17 MPG today, although that's not really a valid test...too short.

Actually, I've seen comparatively few cooling problems on well
maintained LAs, but absolutely none on Bs or RBs. Chrysler easily had
the best stock cooling systems on the road during the V8 era. My
expereinces with FE Fords backs that statement up for certain!

 

Test idea: The LA aluminum water pump casting has a large weep hole
just forward of the lip seal. I'm going to temporarily plug it with
some cork/asphalt refrigeration insulation (sticky, air tight when
compressed) and see if it stops. The pump's getting changed out
anyway, but this should prove the lip seal good or bad...and be a
quick and easy test for same in the future.

 

You know, I'd forgotten that this was the era of the 3/4-inch thick
single-core radiator at Chrysler (the last M-body left our family in
about 1998). Those things are pretty pathetic. I'll betcha you might
have a a fairly high percentage of plugged tubes, even though the total
flow is still OK.

Also, you might replace the radiator cap, just for grins. I've seen it
work miracles.

I've got >400,000 miles on a 318, and its rarely had any issues. But the
thinness of that timing case coolant passage seal and the propensity for
it to corrode always worry me. I really like the big-block "no water
ever passes through the same gasket that oil passes through" approach.
Well, except for the head gasket- but then those 17 head bolts per head
do a good job of keeping it intact

And Ford FEs aren't a fair comparison.. There's something about the blue
oval on the grille that makes cars overheat and catch fire (I'm
actually a Ford fan, but sheesh they've had a long history of weak
cooling systems).

 

The forward bearing isn't air tight, so plugging the weep hole won't
stop air. The weep hole's really just there to let any water that gets
past the seal drain out before it gets to the front bearing.

 

I'm inclined to agree, but in defense of the old single row core, this
car, when things are working properly, never gets above about 205-210°
with a 195° stat, even on the hottest days. However, if only 10-15%
of the tubes are plugged, it would seriously impact capacity.

New Stant, no help there.

The FE's cooling system is a joke in comparison even to a 318...small
passages to/from the pump, low pump capacity, overheat at the drop of
a hat in traffic...I've seen it all! Ford small blocks seem to be
better, but exhibit similar traits. The 335 engine (429/460, etc)
also seem to have their share of cooling problems.

 

Well, it DID slow it down...very little air in the system this
morning, never got much above thermostat temp. Pump
changeout...uh....soon...when it's below 105 outside!

 

The fact that it CAN pull air in past a seal at all worries me- it would
seem to indicate that the cooling system is never pressurizing, or is
pressurizing late. Are you running a "partial pressure" type rad cap
(the kind where the metal disk in the center of the gasket dangles
freely) or a full-pressure cap (where the metal disk has a spring to
keep it tight)? Older Chrysler service manuals recommend a
partial-pressure cap, but I've found that (at least in my climate-
central Texas) a full-pressure cap is the only way to go. With a partial
pressure cap, I steadily lose coolant and often the cars will "burp"
coolant out the overflow tube when you shut them down hot. Never happens
with a full-pressure cap.