Not necessarily true. I meant that it is not holding proper pressure. It should hold 9 to 15 psi, it may only be holding 3 to 5 psi. It won’t boil over, but wii overheat going uphill. Seen it many times.
It could be something else, but if you have to go to a garage to get a pressure test, it could cost more for the test than the cost of the cap, and you will probably end up buying the cap anyway.
I’m not a fan of throwing parts at a problem, but based on experience, I would for this one.
If the cooling system is only holding 5 PSI, how can it operate at 250 F without boiling over? The radiator cap isn’t controlling the temperature, it controls the boiling point.
Water boils at 212F, a 50/50 mix of coolant has a boiling point around 284F.
It states on the container that the boiling point is 265 F with a 15 lbs cap. Without the cap, subtract 45 degrees.
Has the speedometer been recalibrated to be accurate with the bigger tires?
If not, then your speedometer is off by about 12%. Meaning that at an indicated 80 MPH you’re really doing just under 90 MPH. Your odometer would be off as well.
Post 17 states that the speedometer has been calibrated.
The “pinion factor” can be adjusted with the Starscan, just enter the tire size or rotations per mile of the new tires.
Speedometer was recalibrated at the time the new tires were installed.
A good scan tool can monitor and display a great deal of data and record data for a short period. It would be helpful if manifold vacuum, RPM, throttle position ,engine temperature and road speed were monitored and recorded when the problem was occurring.
And if the vehicle has AC it might be worthwhile to gain access to the gap between the condenser and radiator to ensure that there is no debris restricting air flow.
I like history. Did you buy it as equipped? Has it always overheated going uphill? How long have you owned it?
Absolutely @Cavell. I have dismantled customized four wheel drives and reassembled them to near original for owners who bought ‘shock and awe’ only to find that in daily use there was a great deal of shimmy, shake, steering pull at highway speeds, poor braking, poor mileage, etc., ad nauseam.
These are really minor modification. The gearing sound correct. I still suspect it is a case of a radiator problem.
After all, pushing a vehicle at 70-80 MPH that has the aerodynamics of a barn is going to generate heat in the engine. A heavy duty radiator, an oil cooler, and possibly an auxiliary transmission cooler should take care of it.
“aerodynamics of a barn” does sound like an appropriate discription @Purebred. I’ve driven quite a few ‘real’ Jeeps and only exceeded 60 mph once. And once was more than enough for me and it was totally stock and in excellent condition.
I had a CJ5, but that was in the double nickel speed limit days. Mine had the 304, so it was loafing at that speed.
Dumb question: how would this speedometer be recalibrated? Is this done by software or hardware?
Flushing the cooling system will do it for you. My theory is that there is either no antifreeze in the coolant, or an insufficient proportion.
Antifreeze used to be sold in concentrated form. You diluted it 50-50 with water. (Keep an old antifreeze jug around. When you get a new jug, pour it into the old one until levels are the same. Fill both with water and shake.)
Now they also sell antifreeze that’s not concentrated (use straight from the jug) as well. It is possible that the prior owner bought this form without realizing it and diluted it further. You could test this with a hygrometer–the old-fashioned kind with four beads in it–but you might as well just change the coolant.
Has anyone besides me noticed that the non-concentrated form is MUCH more expensive than the concentrated form? A gallon of concentrate costs $16 and makes two gallons for a cost of $8/gallon. The non-concentrated form costs $14 per gallon and has to be used directly.
Yes, insufficient antifreeze can result in slushing up and if the slush gets thick enough it won’t flow. But I can’t understand how there was no overheating until 70+mph going uphill.
I prefer the full strength, must-be-diluted form. After draining and maybe running it with plain water for a while, drain that out. Follow the spec for cooling system capacity. Put in full strength antifreeze, 1/2 of that volume. Then add water, the other 1/2 or a little less. After some driving to circulate and mix it, and a cool-down, top up with plain water.
Unless the vehicle was in a crash and repaired I wouldn’t suspect anyone would have tampered with the coolant.
Maybe this way:
–Radiator frozen up and stays that way at 75 mph in subfreezing weather.
–Heater on full serves to cool the engine sufficiently until it has to work really hard on that long uphill pull.
It’s what happened to me in 1973 on a trip through the Ozarks. (No non-concentrate coolant then–just overdiluted. I always mark the jugs now.)
Come on guys&gals, if there was no or insufficient antifreeze in the coolant, and the radiator froze up, there is no circulation, it would overheat at 20 MPH.