Was only a short time ago I cleared out the cooling system using Prestone Flush Cleaner and filled with 50/50 Prestone coolant/antifreeze.

I rechecked the level inside the radiator only once after running the engine to tune the carburetor and seeing a small coolant spill on the ground afterward.
Only needed to top it up with about a pint or 2 of water so I didn't think anything about it after that. Also had only taken the car on the road a couple times anyway, one of those being yesterday to get brakes fixed.

Well, today I went to get new tires put on. Had to drive same distance as yesterday and I didn't recall seeing the temp gauge looking abnormally hot that time. Was 80's temp sunny day too. Maybe 200 on the gauge.

Only looked at the temp on the way to town today and again it looked normal. Got the tires put on in the afternoon and was driving home when about a mile away I noticed it was up to the red/orange high temp mark.
Had to go uphill a little at that point too and the engine began to knock. I was so close to home I just couldn't stop, thinking I would be waiting an hour for it to cool down with only half mile to go I pushed on. Wished I could have used better judgment.

Road leveled off but last part to my driveway was halfway up a steep hill, thought I could speed up enough to help with momentum and slowly move uphill for the last part. Engine was knocking just from accelerating so that made me slow up and I got up the hill at around 15 MPH knocking terribly all the way. Gage needle went as far as it could toward danger end.

Pulling into driveway smoke was billowing from under the hood, was the oil from leaky valve covers/gaskets I'm replacing soon. Opened hood and let it cool down a bit and eventually refilled the radiator slowly to let water heat up as it went in. Took a while, and when doing so I poured a little onto the water pump and it boiled off.

I'm guessing the radiator cap is bad, says 15 PSI on it and I was finding info saying these use a 16 PSI cap. Not much difference anyhow. Reason for believing that is because it was allowing some water out at normal temps when I was tuning the car, mostly idling but some revving.

Another thing... I broke the overflow hose nipple off the radiator fill neck, almost first thing I touched when looking over the car after buying it. That's how I was able to see the coolant getting out fairly easily.

Stupid of me not looking for the level in the radiator after any driving at all, I shouldn't have trusted it to be okay until I had more time with it.

Any thoughts, advice, similar experiences?
I know I'm going to replace the cap regardless, but radiator itself could be the problem from the look of the inside.
Oh, and if you think I damaged the fragile parts of the engine (seals, etc.) or worse, let me know. I can take it! Well, not I can't but I've no choice.

 

That's the same reason that I installed an overflow "jug" on my project.
It lost a little coolant each time the engine was stopped.....then I got a high reading on the temp.gauge one day, but I pulled over immediately and let it cool down for 1/2 hour---then added coolant from a container I had in the storage compartment until I could get home which meant stopping/cooling down three more times. Turns out the new thermostat was stuck closed/it actually had scrape marks where it was sticking.

With the overflow jug installed, the cap will relieve pressure into the jug when the engine is stopped....then within an hour or two the radiator will siphon the extra coolant from the jug back into the system.

As for the knocking engine.......no comment since I'm a rookie.

 

I would have been smart to stop like you did. In fact, I was so close to home I could have walked there and back with some water, helping the car to have time to cool down too. It was only at the red mark, so engine off right then sure would have been better than pegging the gauge to the end (280+ anyhow).

I have the overflow jug there, just no connection because of me breaking the hose off at the radiator. I wondered if these were able to do a siphon back to radiator. There's the 2nd hose connection at the jug cap but no hose there.

I was planning to JB Weld a way to connect the hose onto radiator again, I just didn't realize the radiator would be going empty so fast. Or possibly just boiling off from lack of pressure due to a bad cap.

I'm going to check the thermostat, replace if I find a problem with it, but flow was okay at the upper radiator hose on there judging by it's feel when I was flushing out the old crud and putting in fresh stuff.

I don't understand why it would be so bad about losing the coolant after only 40 miles on the road, that's what I wasn't expecting at all. Seller had replaced the water pump so that's still new but the radiator had rusty, muddy water in it and that was also a surprise. Buyer mistake there, I didn't get a good look, only enough to see it had liquid in there when I was going over it before the buy.

 

Look for white smoke in your exhaust now.. the likely result is a blown head gasket from the extreme overheating ..hence the knocking sound.. heads were so hot, it was detonating .hopefully no piston damage . depending on your type of oil, you may not have done any bearing damage ..Synthetics can take about twice the heat of dino oil. Next time... STOP THE ENGINE AND WALK!!

 

Yeah, worried until checking for that.

I was looking for a bad sign at the tail pipes when I bought it, expecting some smoke whether oil or water, but it only looked like puffs of vapor at the very first.
Car hadn't been started before I got there because the key was locked in the house (yet-to-be mother-in-law). That was good to see nothing after the initial start up. Too rich gas smell though, which still seems to be there slightly after my tuning on the carb.

So.... started it today and ran it for a several minutes. Revved up to 2500 RPM briefly after warm. Same good-looking exhaust. Whew!

The oil that's in there was still fresh according to seller, and looked it.
Didn't think to ask what kind, was going to be one of the first things to change out, along with getting transmission and engine pan gaskets replaced. Leaky right now.

The last thing I wanted was something to go wrong because of me. I should have opened the cap on the radiator after that first long drive (well 25 miles round trip aside from 1st drive getting it home). Was probably nearly dry before the 2nd 25 mile drive. I thought I smelled something 'different' when getting gas in town after the tires were put on.

I have a boroscope/endoscope camera which I used to look at the 2 and 6 cylinders when I checked those spark plugs. No heat shield that side. Couldn't get to others easily so skipped the rest. #4 wire boot is stuck otherwise that would have been simple too. Found the gaps to be 0.050" so I changed them to 0.045", looked fairly good other than oil getting into threads from leaky valve covers. Maybe some oil burn on part of the insulators, or partly carbon from having been run so rich before. Not sure what.

Oops. Lost my train of thought there. That was before this overheating happened. Going to be anxious to see other cylinders later.

Feeling lucky for the moment anyhow. Nice to have good with the bad until next thing comes along.

 

If it's the white plastic (or yellow if its real old) then it does siphon back.. Not sure how the hoses hook up.....

 

Yeah, definitely yellow and I'm afraid to find out how brittle it is too.

There's a tube going down to the bottom from the radiator hose side, if I'm remembering that right.
I was thinking maybe the missing one probably diverts toward the ground and for air flow in and out of the tank as coolant comes and goes.

Found a drawing after 'net search but only confirms the radiator hose side of the "expansion tank" cap, not the other.

So looks like I've got to get that broken filler neck hose back together so I don't lose the coolant.

This is the kind of thing that should be simple to understand but all I ever had to do with my cars and trucks before is fill and forget them, watching for either radiator level or bottle Hot and Cool level. First time I've dealt with a broken system, lucky me.

 

Even without the recovery bottle the car should not overheat. The old radiator systems would just puke out the excess coolant till it found its own level.

A bad rad cap WILL cause overheating/boiling..one pound off means nothing, but the cap must match your system if it has the bottle!

 

Yeah, see, that's what I thought. That unless something were making it possible for the radiator to keep on spilling out or boiling over turning to steam and exiting that way, I figured it would just lose a little over a long time.

I got a new cap, a Stant Lev-R-Vent, part number 10330 and it's 16 pounds. New seals on it make the old cap look shabby, to say the least.

Also got a 180 thermostat (expecting only Spring to Fall drives mostly) to put in. Even though I haven't even removed the old one yet. I will probably find the original 195 in there.
Maybe nothing was wrong with it, seemed to be doing what it needed to do in the right way. Just makes me remember all the way back to my first car with its 350 Chevy engine and I found it to be causing a little trouble.
This old one probably has an accumulation of rusty crud, unless my flush and clean worked miracles on it.

I should be able to get the bottle hose reconnected to the radiator fill neck fairly easily, just enough remnant hose nipple left. Add JB Weld and a high temperature sealer, problem solved... hopefully.

Oh, and I'm going to check for collapsing hoses too, having read about that round here in the forums.

 

180 thermo is perfect for all seasons, keep it.

While its out fill up the coolant thru the opening, then install the thermo and housing. Then fill rad up to the top, bottle to full line