Overheating 1968 230s

[Scutch]

My car is overheating. On a warm day, it heats up fast when I am
idling at a light. It will get halfway between 180 degrees and the
next white mark. When I continue to drive it will cool down but after
about 15 minutes of steady driving the needle will have risen most of
the way up to that white line above 180. When I turn on the heater
the temp goes down.


I have replaced the thermostat and flushed the system. The water
seemed to have a slightly rusty color as I got more and more of the
anti-freeze cycled out. I put just water in and ran it for a day to
see if the coolant continued to have that brownish color. It was
very slight if at all. I put 50/50 anti freeze in it today and drove
around in low 90's weather. It overheated, or at least got hot. I
haven't allowed it to get over the white mark between 180 and 250
degrees. The thermostat appears to be working as it should.

I wrote earlier about having foam come out of the tube above my
radiator cap. I think the fluid came out because I released the
pressure one day and I was low on coolant. I wanted to see what was
going on when the car was overheating. Was the fluid low? It was
about an inch under the cold level metal thing. Since flushing the
system I have not gotten anymore foamy symptoms.
And before I flushed it, sometimes I would look under the radiator cap
and see some bubbles and foam, sometimes not.
I have heard the opinions that it is definitely my head gasket and
have been hoping it is not, but I am unclear how to exactly diagnose
this.

I also have this exhaust leak coming from this A.I.R. system on the
driver side of my engine. It is fairly pronounced, and from what I
can tell, would be an exhaust leak on every cylinder because this AIR
system is hooked up to my head with a small tube coming out of the
head just below each spark plug. In part of the system there is a
vacuum line that runs to my front carb. I have blocked that off.
Can I let this exhaust leak go for now or can it damage something? Valves?


My timing is fine and so is the mixture. The car seems to run just
fine. Although the hotter it gets the weaker it is off the line and
the lower it idles. But the idle does stay steady. The oil doesn't
appear to have any coolant in it. When I look under the oil filler cap
I see nothing unusual. I do smell coolant (once or twice a week)
occasionally when I am driving. But I also know that I have a small
leak in one of the seals at the bottom of the heater core where the
vents into the driver compartment open and close. The leak is not
enough to make it to the ground.

The only subtle things I have noticed lately and I am not sure if they
are related is that when the car idles in drive it seems to make a
vibrating sound almost as though the car is in a slow, back massager
chair. It is slight, but a bit noisy. My idle speed is not high. It
seems like it has something to do with the way the engine and the
transmission interact. Also, at high speeds the car has this
vibration that is subtle, but comes in waves. It sounds like when you
are sitting in the back of a jet plane, sometimes you can hear a
vibration coming from the engine. The sound swells and then quiets
slowly, over and over. These may not be related, but I am mentioning
them anyway. Both sounds are new in the 6 months I have owned the car.

I tested the compression hot and got 130 psi on all cylinders.

My big question is how do I get a definitive answer about this head
gasket? I have heard mention of a leak down test, but am unclear how
that goes, and wonder if that A.I.R. exhaust leak will screw with the
readings. Can a bad water pump also be a factor in overheating?

One last thing, when I drained the radiator of fluid and then filled
it up with the mix and then started the car, the thermostat did not
seem to open and the temp gauge got close to the red mark, so I shut
the car down, after a couple times of this, with the radiator cap off
the thermostat must have opened and what seemed like Satan's breath
came up from the radiator and all the water went down, into the block,
correct? Does that indicate that exhaust is leaking into the cooling
system? And that is what is happening with a blown head gasket,
right?


Sorry, I am a bit unclear about the intricacies of the cooling system
and the repair manual I have is a bit anemic on the details.

One very last thing. The last thing I did that was major to this car
was I pulled the exhaust/intakes because I had a crack in the exhaust
manifold and was having vapor lock. A new fuel pump ended up fixing
the vapor lock. On the new exhaust manifold I jammed the heat risers
in the always blowing straight to the muffler position. Since putting
the manifolds back on I think I may have damaged the manifold gasket
because I now have a very slight oil leak which appears to be coming
from under the 2 or three ports closest to the firewall. By slight I
mean a few drips per night.


Thanks for any help.
Eddie

[ggenovez]

Don't fill the radiator to the top. These cars don't have an expansion tank, therefore it bubbles and burns on the block making an awful smell.

When you drained and refilled the coolant, did you remove the cap and let the thermostat cycle a few times?

This purges any air bubbles in the system that could be preventing the system from cooling properly.

Also does your fan clutch work? when you're overheating the fan in front of the enginge should engage and help cool.

Do you have an auxiliary fan mounted in front of the radiator? does that work? Ground the wire over the thermostat housing, if it's there, if that works but the fan never kicks on, the switch in the thermo housing needs to be replaced.

Good luck.

[Scutch]

Thanks. I did not cycle the coolant a few times with the cap off. Will try. I only have a fan attached to the motor. One fan only. It turns all the time.

[ggenovez]

Ok, purge the air.

The fan spins freely cold, but when it gots hot enough it will engage, Spin it cold and spin it when you're oveheating, if it hapens again after the air purge.

Also when you look in the rad, there is like a bump, that's the top of the coolant level

[todds]

You said it stays cooler with the heat on? How old is your radiator? It should be able to stay cool without the heater core even connected (mine is plugged off for the summer)

That thermostat sounds suspect to me. They are so cheap, after you get it bled of air and filled to the proper level, if you still have the problem I'd change it out again just to be sure. The thermostat recently went bad in my car, it does happen from time to time.

[Scutch]

The thermostat seems to be opening fine. I can see the movement in the fluid when the switch opens around 180 degrees.

I also checked the fan clutch which seems tight when the car is hot.

I am gonna get the radiator rodded tomorrow.

[300SDog]

I would suspect the water pump. Iron blades on the pump corrode down to nubs. It aint like the pump either works or not, more like insidious wearing down of blades rusted and pitted makes it less efficient.

Compression at 130 per cyl without variation is excellent, doubt the head gasket is blown. Vibration culprit sounds like tranny and engine mounts, also check flex discs as matter of course oughta not be cracked. Folks generally replace flex disc if its millions of yrs old when doing the tranny mount. And when replacing tranny mount its wise to paint mark position of the old one on track. If you just throw tranny mount in there any old way then driveshaft orbiting can occur from tranny not being alligned straight with mounts.