Cooling question

I'm working on the 1968 Ford wagon, 390 big block. I just; installed a temperature gauge because things seemed quite hot even though the car wasn't bubbling over. The gauge showed 215-220 at steady cruise, about the same at idle. Replaced the thermostat, flushed the radiator and replaced the coolant. Still hot.
In a last ditch effort I pulled the thermostat entirely and now it's running 190 at steady cruise and 195 at idle. So now it's cooling, but pulling the thermostat seems like a pretty crummy solution.
When the thermostat is out water gushes through the radiator like it's Niagara falls. With it in, not so much, though if I let it get hot with the cap off you can tell it's circulating at least a bit.
Any ideas? Could my water pump be on it's way out? I'd like to fix this properly.

Yeah, I'm with you about it most likely being a water pump issue. I'd look into it pretty quickly. OBTW: those FE engines have VERY low idle oil pressure, like in the single digits.

Water isn't supposed to blister through the system. Half sits in the block all hot and stuff, the other half is cooled by the radiator. When the thermostat says, "OK I'm hot enough", it opens to let the cooled water into the block and the hot water over to be cooled by the radiator.

With no thermostat all of the water is the same temp all of the time.

I would try a radiator, heater core, block flush. Douche it really well and try again, as designed it's supposed to work.

...or throw money at it.

In my experience, 390s always seem to be on the hot side. And having that BIG chunk of iron it will radiate heat and retain heat more.

With a car this old, I would change the water pump as the next step just for piece of mind in the Texas summer and due to age. While your temps are not overheating, they are above normal...even for a Texas summer. My first thought was that the vanes in the water pump are partially gone and not providing adequate pressure to push the coolant fast enough through the thermostat and enough to rush it through the radiator without the thermostat.

What engine and setup do you have...2 bbl or 4 bbl carb? Is it an air conditioned car? Air conditioning cars will have the 4 core radiator and may need a little more work to insure that it is flowing. Might get a radiator shop to rod it out.

I take my cooling systems seriously as I also live in Texas and have done old Fords all my life so I look at 3 things first.

1. Do I have good info? Is the gauge accurate? You seem to have that in hand. What are the normal temps? 200-210 degrees would not be out of line for Texas summer idling and up to 220 if you are running the air conditioning. A lot of folks panic if they see anything over 200 and think that cooler is always better.

2. Engine too hot? Is it making excessive heat? Carb adjustment (too lean?), plug choices and choke settings can bump the temp some.

3. Not cooling properly? Airflow proper? Got leaves and bugs clogging things up? fan not pulling air? Have you got a shroud on that fan? Coolant flow O.K.? This is where you have been working and seems to be the most common area with problems. Get out the clogs and insure the proper flow.

Sorry if I seem to rattle on, but I have been walking my nephew through his 69 Mustang and the importance of fixing systems rather than just fixing the currently broken part. I did the brakes from pedal to drums before he got it...finally wrestled him past the cooling system where he slowly worked his way to replacing everything. I think he got the idea when he did the fuel system as he finally understood that he had to understand how these things work together. He had his steering box crap out on him and I got him a rebuilt unit so he could spend his money on bushings, bearing, ball joints, shocks, springs and tie rods! He has not had any drivetrain problems...yet! But he has been looking at rear axle and driveshaft rebuilding resources.

Heaven help him if he starts getting electrical problems!

Bruce

Thanks for the advice. A new water pump is $39 and I'm picking it up after my son gets his braces off. I'll do a flush and then change the pump and reevaluate. It is an AC car though the AC isn't currently operable. The radiator is huge, but it also has the biggest condenser I've ever seen in front of it.
I'm finding that getting these older cars back into shape is really a process. Watch it, listen, tweak it, make it a little better here and there. It's fun.

Cleaning the air side of the radiator helps too. Especially if you live in an area with cotton wood trees. The condenser should be cleaned too.

They're clean. I made sure when in the car and then doubly sure when I pulled the radiator yesterday. I love the brass end tanks under the flaking paint on the radiator. I kind of want to polish them.

Don't forget to try the radiator cap.

Radiator cap won't affect temperature. It will only affect the pressure at which coolant is allowed to go into the overflow. While it's such a cheap part that replacing it is almost worth the $5 just for peace of mind, i dont think it has anything to do with this problem.

Yes it will. By adding pressure it raises the boiling point of the water.

and remember, some of these cars were INTENDED to run at around 220 or so.

most stock thermostats were 195, with a warning light set at 250 or so.

220 isn't nothing to worry bout, in my book. 230+ is.

trying to force it to stay at 180 may or may not happen.

also, look into 3 core champion radiators. usually fit pretty good, and do great at being a cheap lightweight, effective radiator.

also, make sure your lower hose aint sucking shut on ya.

Michael

After some checking I see that 215-220 is the correct range. But a rebuild of a 45 year old cooling system will give you great peace of mind.

Just to add some info...a vacuum leak can cause a lean condition that will up the temps some and my brother and he informs me that improper timing can jump the temperature too. This could include worn distributor components and Pertronics is your friend. With 3 69-70 Mustangs, a 57 and a 65 Ford truck, a 66 Thunderbird and a 68 Mustang among my family and friends projects I have been boning up on my ancient secrets.

Just looking into coil polarity was eye opening.

Bruce

My old Le Mans ran chronically hot despite lots of dinking around trying to figure it out. FINALLY I realized the timing was off and setting it right cured the issue.

Yes it will. By adding pressure it raises the boiling point of the water.

Sure, but it doesnt change the temperature the car runs at. It just changes the pressure at which coolant is allowed out of the radiator. Think about it.. i'm right.

The only way a radiator cap can cause a car to overheat is by letting it push coolant out when it's not supposed to. Then it overheats from not having enough coolant. And it's pretty damn obvious when it happens. Other than that, there's no way that a radiator cap affects running temps.

I've checked and rechecked the timing. It's 6 degrees BTDC with the vacuum line off the advance canister. That goes by the book. Hooking up the line brings it to 30 degrees at idle which is right where everything I read says it should be. What is total advance? I don't know. I haven't had anyone hold the throttle open and even if I did, I don't have a tach to figure out what the advance vs. rpm is. A duraspark distributor is on my list of things to do.