1986 Ford Ranger 2.9L Overheating PLEASE HELP!!!!!

Okay guys thanks for adding me to the group!! Here is my question.
I have a 1986 Ford ranger 2.9L Automatic with 40k original miles such a beauty and flawless.
Well my baby is running above normal. So I live in California and the temperature in summer time right now is 105 degrees in the winter time I have no problem but right now she is running after 30 mins around the A and the L (NORMAL)
I would say that's above normal but it never over heats though.
I have changed my radiator cap, I have purged my system of air bubbles, I also have cleaned out the radiator. Oil looks great there is plenty of coolant in the reservoir, and there is no white smoke or moisture coming from exhaust.
However, my radiator doesn't have a cap but I was told its not pressurized so it doesn't need one, its more like a plug rather than a cap. So I don't think that's the problem. I am stumped. I don't know if its the water pump its not leaking however its 29 years old. Can you guys give me some advice?? I could really use it. Thank you in advance GO RANGER GO!!!

EDIT: I meant my reservoir doesn't have a cap guys sorry. I bought a brand new cap for my Radiator. I added a plug today but I was told the reservoir was not pressurized there is not lack of coolant after i drive the reservoir liquid is still in the same location. If it is pressurized I might as well just buy a new one but all the after market reservoirs have the mounting brackets on the side but mine are on top. Sorry about the confusion. Please help and thank you to those who have responded.

The radiator should have a pressurized cap, the overflow tank is not pressurized. If it actually your radiator that has no cap you need to get one for the system to work properly. If your overflow tank doesn't have a cap you need to get one to keep dirt and other stuff out of the coolant.

Yes ^^^ +1

All radiators used pressure caps since the 1950's, this raises the boiling point of water or water/coolant, so prevents boil over better.

Newer cooling systems added a TWO WAY radiator cap with an overflow tank.
When you heat up a liquid, any liquid, it expands in volume, that is where the pressure comes from in the cooling system, and if you ever used a pressure cooker that where it's pressure comes from, expanding volume of a liquid inside

As the engine heats up the coolant the pressure in the system goes up until it reaches the Rad caps pressure rating, say 14psi, at 15psi the larger valve(big spring) in the cap is pushed open and coolant flows out the overflow hose and into the overflow tank, larger valve closes when enough coolant exits and pressure drops to 14psi again, all this is totally normal and happens almost every time you drive a vehicle longer than 20 minutes or so.
After you shut off the engine the coolant cools down and shrinks in volume, so pressure drops, it eventually gets down to 0psi, and then -1psi, negative pressure, that's when the smaller valve, in the center of the rad cap, starts to open and coolant is sucked back in from the overflow tank, this keeps the coolant in rad "topped up".
And this is why it is very important for the overflow hose to be in good condition, and the overflow tank to be clean, debris in this tank will settle at the bottom, hot coolant coming in will push it out of the way, but it will settle back to the bottom and prevent coolant from being sucked back in to rad when engine is cooling down.


If you have never changed the thermostat on this engine then it might be do for a change, and the water pump as well.
Low mile engines often suffer from internal corrosion from long periods of disuse or very short drives, under 20minutes.
The water pump impeller blades may be eaten away lowering circulation.
Thermostat is opening but may not be opening all the way so restricting circulation.

Corrosion comes from the coolant's anti-corrosion chemicals, they are gone after 2 years, regardless of miles driven, so on low mile engines people often don't change the coolant thinking it is a "mile thing" like oil.

Some choose to use a 180degF thermostat, factory would be 192degF thermostat, the higher temp t-stat helps to keep oil cleaner, and gives better MPG.
A working t-stat regardless of temp rating, has nothing to do with over heating, an engine is not over heating at 200degF, that temp would be just below 1/2 on Ford temp gauge.
So at 200degF a 180deg or a 192deg t-stat would be open all the way, so coolant circulation would be exactly the same with either.
So really a users choice, running engine 12degF cooler isn't "better" or "worse" for the engine, just the oil and MPG.

2nd update

Thank for the info guys. Here is what I have done.
I have purchased....
Radiator Cap 13psi
Cleaned out reservoir
Flushed system
purged system of air bubbles
Bought brand new thermostat

There is not white smoke
coolant levels in over flow are not dropping.
No moisture in exhaust

The only thing i think it could be is the Water Pump but its not leaking.

The truck has very low miles the person i purchased it off of never drove it when i got it i put 10k on it already it drives like a dream just the heating up is the problem.
It runs at the A L on NORMAL after 30-40 min drive in 105 degrees weather.
There is no problems on cooler days but it suffers only on hot days.

Do you have A/C? With A/C the air has to go through the condenser first, if that is blocked it could cause overheating problems. Of course using the A/C on a hot day will increase the heat. There could also be an air flow issue through the radiator (bugs/dirt). The other thing to consider is an internally blocked radiator which will reduce the flow/cooling of the water. Since you have an automatic transmission you also are adding heat from that into the cooling system.
About the only things left to do for your cooling system are a new radiator,~$60, and water pump, ~$35.
The radiator is easy to change, the water pump takes a little more time but is worth doing at the same time since you have the system drained.

2trux

Hey Sir thank you for the reply.
Yes I do have an A/C. Condenser works great as well, all is up to par on that but I don't use it because there is a leak somewhere so it doesn't hold freon. So until I Fix it the A/C is not in use.

I am going to purchase a new Radiator tonight and water pump and change it.
I mean its a 29 year old vehicle but the person I bought it from kept it in really great shape It came with all tune up receipts I basically got a new truck It seemed like it had a lot of problems from sitting so i assume thats why I am having this problem because out of a whole booklet of receipts there is no waterpump nor a radiator change. It had like new headgasket, electric window motor, new heater core and much more.

Ill keep you updated see what happens with the new parts!
Thank you again for the feedback