First long road trip in a few years in the general, overheating

[Beach_Dude]

Current configuration:

Motorcraft 4350
MSD Distributor
MSD 6AL ignition
Factory exhaust manifolds
BJs Factory Replacement Radiator
BJs Aluminum Fan Shroud

Weather was 100-105F with the AC howling.

Firstly, the heat riser I bought from some FSJ retailer sucks. The spring is too tight and regardless of heat, never drops the valve open. Thinking about cutting and modifying spring/weight. Overheated on the first attempt up mount Whitney. AC was turned off for the mountain drive and still overheated.

One night I figured to unwind the spring on the heat riser, which allowed us to get up mount Whitney, but still, too hot and had to stay in 2nd gear.

The main indicator that something wasn't right was that at 65MPH the heat was 30-50% up the dial which is WAY TOO HOT for just cruising flat land.

Also, any incline would require 40-50MPH just to stop it from going above 60% heat on the dial.

I have the distributor at idle just a few degrees above stock, maybe 2*, but I have the limiter set advance set to factory timing.

I have a thing for leaving the General in OE configuration other than ignition, for obvious reasons And it breaks my heart to thinking that I should get a cross flow radiator and shroud, another $800 blown...

Besides the heat riser, wtf am I missing?

[Full Size Jeeper]

I would jam the heat riser open for starters and give that a try first. Also do you have a temperature gauge with numbers? Even if it was just a temporary install to see where you are really at. Lots of places to look. Also what fan are you running?
1. Is the lower radiator hose collapsing and slowing coolant flow.
2. Is the the air/fuel ratio to lean.
3. Late timing will allow the fuel/air mixture to continue to burn while the piston travels away from TDC. This causes a lot of heat to be absorbed into the cylinder wall that wouldn't ordinarily be there. If extreme enough, exhaust gasses will still be carrying a lot of heat w/it. This heats up the exhaust valve, seat, port and the surrounding water jacket has to try to absorb all this additional heat. The result of it all can be an overheating condition.

[Beach_Dude]

First things first... Even through I've used nothing but distilled water and coolant in there, I'm shocked at the mineral deposits inside the core. So, i'm gonna plug it and soak it with vinegar for a few days... Hopefully that eats up any/all calcium.

Secondly, I'm gonna try setting the timing a degree lower and see if that helps. There's no reason why it should be overheating by that much since it's on specs for a 78 engine, and taking that into consideration given that I used to have a Duraspark on it at 10 degrees and it was fine.

If anyone has any pointers or recommendations, give a shout!

[Full Size Jeeper]

I used this to clean my radiator. It was out of the jeep at the time. Duct taped a plastic bag over the lower hole. Worked great!!!

[SJTD]

In da good ole days they had a two part coolant system flush. I think Prestone sold it. Shiny chrome tube package.

First was oxalic acid which reduced the rust, meaning converted it back to iron. Since rust is about ten times the volume of the iron it originated from it loosened up and was flushed out. I suppose it also dissolved any calcium deposits.

Then there was a baking soda as a neutralizer.

They still sell it? Haven't seen it but I haven't looked. Can sometimes find oxalic acid in the paint section of better equipped hardware stores. Used for bleaching wood.

Idunno if it's safe for aluminum. Can should say. Test if you buy it for something else.

[letank]

manifold vacuum instead of ported vacuum... going to Mt Whitney is a slight graded climb from LA, using 395 going to Lone Pine I suppose... Mt Whitney trail is not open to 4x4, but Whitney portal is a nice climb short of 8000'



and use 14 degrees with distributor vacuum hose plugged... upon restart the idle will be a bit higher... adjust


Also the 4350 does not have the altitude adjuster... you might be running a tad lean... and the gas with ethanol is burning differently, it is considered leaner as well


copied from https://extension.psu.edu/fuel-ethanol-hero-or-villain



Another effect of the oxygen from ethanol is that ethanol blends tend to run "leaner" than pure gasoline because there is more oxygen available in the fuel-air mixture. If your engine is not able to compensate by reducing the incoming airflow, the resulting combustion conditions in the engine cylinder may be less than ideal.


Of course... do you trust you coolant gauge... double check with a non-contact thermometer on top of radiator, thermostat area and upper and lower radiator hose

[Beach_Dude]

Ended up switching out the Thermostat yesterday, drove down the 405 for 10 miles at 75MPH, hit the toll roads, uphill full throttle, barely any increase in normal operating temperature.

Then I stop in the gas station this morning as it's warming up, 2 to 3 minutes at most passes and the temp gauge goes up to half way+ on the gauge.

The gauge is accurate and what makes this idea come to light is that the front of the body gets SUPER hot with the AC on. And I mean barely touchable. I'm starting to think that my AC is experiencing a high superheat problem. Here's the way I look at it... If the high superheat is 275' F as it goes to the condenser, it'll cool the radiator and over heat the engine.

Going to add a quarter pound or increase my low side by at least 2 psi and see if that helps.

Ideas?

Also, Home Depot has 30% white vinegar instead of 5-6%. Gonna let that sit in the radiator and I'll watch the calcium wash away hoping it won't eat the radiator and welds up. Apparently the acid in vinegar doesn't chew them up... We'll see.

[SJTD]

If the high superheat is 275' F as it goes to the condenser, it'll cool the radiator and over heat the engine.

Huh? Cool the radiator and overheat the engine?

[Beach_Dude]

Heat the radiator... Not cool. Muh bad.

[wiley-moeracing]

If your going down the freeway and your experiencing over heat you have a flow problem, the fan should not do much as long as you are getting ram air through the radiator. I would use a thermometer gun and check your radiator surface at the inlet area, in the middle and outlet area, top to the bottom and see what the difference is. you can have too much flow or not enough flow. I have had new radiators clogged up from the dealer, especially the aluminum. As far as your a/c goes, same applies to the condenser, it may be plugged causing the over heat/high pressure in the system. Cooling issues are a pain but if you take your time you will figure it out.

[rapom]

I believe I have a similar problem. I don

[Tripwire]

IIRC there is supposed to be a spring thing in the lower radiator hose that stops it from " sucking shut" at higher RPM's ?

steve

[lkmarsh]

Both hoses should have safety springs inside, a stuck thermostat will
collapse them both. Does your fan sit inside the shroud at all?
Seven blade factory fan with clutch? x2 on a real temp gauge.

[SJTD]

I'm unclear on how that can happen. It's a closed pressurized system full of an incompressible fluid. If the lower hose collapses where does that fluid go?

If you have the cap off or air in the radiator, maybe.

I figger the spring is a leftover from the old days before overflow tanks when there could be an air pocket in the radiator. Another theory I've heard is it's for the assembly line where they pull a vacuum on the system to fill it quickly.

[rapom]

I have a similar problem. 79 cherokee chief. New brass 3 row radiator. Severe duty clutch fan (Early 80's diesel gm application), shroud. FlowKooler water pump. 180 degree milodeon thermostat. No overheating problems until I run the A/C. I even got a 14" spal pusher fan on the condenser.

I have all new A/C system under the hood hooked up to the stock underdash unit. It blows so cold I have to have the windows cracked and the under dash vents open to stay comfortable.

I haven't really overheated it yet but it gets up to the top of the green area where it normally is in the halfway to 60% green area.

I'm wondering if I should have the condenser placed off the radiator a bit more because what your saying about the condenser heating up the radiator makes sense.

I even disconnected the spring on the clutch fan that it engages earlier. You can heard it roar from inside the Jeep.

Most overheating is when sitting still or going over 60mph. Again, only if the a/c is on. Maybe I ain't overheating but I still don't like the temp to go as high as it is.