Cooling Issues

[JustinK]

Hi all, posting in hopes someone can point me in the right direction. I have a 74 bronco with a 302 and a/c. Its always run a bit hot when stopped especially with the a/c running but it would cool down when I am driving.

I took it in for service after not driving it for a while and had an oil change, coolant changed, oit and temp sensors replaced a/c charged and a belt was replaced with a smaller size as it was squeaking when started.

After the service i am running 210 - 230 without running the a/c and not sure what the issue is. Now when driving the temperature drops but not much lower than 210. I added some water wetter to the coolant but that did not do anything.

The water pump was replaced about three years ago and i have no fluids leaking from the truck. I started the truck with the radiator cap off and coolant appears to be moving. The speedometer was rebuilt about two years ago so don't think it’s a gauge issue.

I need to take it back to the mechanic but not sure where to start. It seems like it has to be one of the items i had serviced as it was different as soon as i drove it home.


Thanks!

 

[Madgyver]

fan shroud?
Stock Fixed pitch blade or flex type?

 

[Chiclassics]

Fan could be issue...just put your hand around top of engine to see the air flow...if its too much air flowing above then put a shroud. if air itself is not enough then change fan. Are you running automatic transmission? sometimes an overheated transmission overheats coolant which in turn doesnt cool engine enough

 

[ba123]

I wouldn't think it's the fan if it cooled before service and then did not after.

Could be air in the cooling system and needs to be burped. Air could be stuck at the thermostat as well. Have an overflow tank or not?

Tried a burping funnel and fill while running to get the air out?

Also, don't change sensors unless they are bad. You're taking a risk of installing faulty sensors. And on that note, you sure the new ones are correct and read correctly by your gauges? Could be misreading. Senders are not all the same.

Lastly, starting it cold with the cap off, you will not see coolant moving through the system. Thermostat is closed. That's just vibration.

 

[Broncobowsher]

The first line of the post is it has always ran a bit warm. So I don't think this is a new issue.

Broncos never came with A/C. So adding A/C is going to stress the cooling system, which even when new was a bit marginal.

Cooling is about flow. Surprisingly little with the water. Mostly air. The creep up at idle tells me that there is an airflow issue. Which airflow I can't say at the moment. Might be not enough fan, or not enough control of the air the fan is trying to move.

The 210 at cruise. Might be airflow? Or it might just be the cooling system lacks capacity? Does it creep up when pulling a long hill compared to the same speed on flat ground?

What fan are you running? Fan shroud? How does the fan fit in the shroud? How bad does the A/C condenser block airflow through the radiator? There is no standard A/C condenser since 100% of them are aftermarket. Are you running a winch?

There is also the possiblility the radiator is failing. Didn't say leaking, I said failing. If the fins come loose from the cores they don't transfer heat. Fin seperation without core leakage is very possible. Water passes through the radiator without giving up heat.

What is going to be bad is it sounds like you don't tinker yourself. Keep seeing references that you are taking this to a shop. Most shops are good at repairing systems that are correctly engineered to start with. It sounds like the A/C problem is likely a design issue with aftermarket parts. This makes changes more complex as it isn't just swapping one part for another of the same but in better condition, it is having to figure a way to engineer a solution, find parts to make it work, and put everything together. All that is time, and time is money.

 

[JustinK]

Hi all thanks for the input. Here is some additionAl info to answer some of the questions asked.

i have an automatic transmission and do have a seal that is being replaced next week as trans fluid is flowing into the transfer case. My fluid level is fine and I read this is a common issue. I guess it could be running hotter than normal but not sure.

The fan is stock rigid with seven blades. The shroud is stock plastic. I was looking into better cooling fans and the fan could be closer with spacers to the but it’s been like that since I bought it. Could be my original problem lol.

I regret replacing the sensors but thought I would make sure my readings were accurate before looking for air flow solutions.

The condenser definitely restricts airflow as it’s mounted in front of the of the radiator with less than an inch of space between them.

Could an incorrect sensor or improperly installed sensor cause the problem. Tighter belt be an issue?

It cooled fine when driving before but would creep up when stopped at lights for any period of time.

Yes, I have to bring it in so looking for some input before replacing the radiator. Any way to test to see if it’s failing And could flushing it have made it worse?

Thanks!

 

[ba123]

Yeah, it not cooling down while driving now is your main issue, and then not cooling down when stopped is your second. I guess I was focused on what I considered your main issue and others were focused on your second issue of not cooling when stopped. So fan still something to think about like others mentions. Sorry for my tunnel vision.

When stopped, fan needs to be close enough to pull air through and also, air will follow the path of least resistance so if there is space between the fan and radiator or if your shroud doesn’t cover the spots where air could also come in the sides then it won’t pull through the rad. You should be able to feel the pull in the front even with the condenser there. A sheet of paper should stick to the front, even with the condenser.

Don’t think the belt could do it, and the sensor can only give you an incorrect reading, not cause overheating.

Was your thermostat changed in this service? Maybe a different temp tstat was pu in.

I’d def get the correct spacer to put your fan as close as possible without any chance of hitting. Nothing wrong with a plastic shroud if it fits properly as well.

But…I think the main issue you have to figure out first is the cooling while driving. If it doesn’t cool while driving, your fan issues don’t matter cause it’s def not gonna cool while stopped!

 

[gnpenning]

You already have plenty of good information. My question is have you checked with an IR gun in different places to verify gauge temp readings and potential hot spots??

 

[DirtDonk]

^^^ this and that…

 

[Broncobowsher]

I have one more idea that might cover all of it. Is the fan put on right? I've seen a lot of fans put on backwards.
There is the angle of the blade and the scoop of the blade. They are different.
The angle determines if it is standard or reverse rotation. For the rotation of the fan, the leading edge is toward the radiator and the trailing edge is toward the engine. If you flip the fan over (front to back) it is still the same.
But the scoop of the blade matters. Think of an ice cream scoop. Go at a tub of ice cream correctly and you get a nice scoop of ice cream. Flip the scoop over and you will put a lot of effort into moving ice cream, but you will get very little for all the effort you put into it. There is a curve to the blade. You want the concave side toward the engine. Often the fan will fit either way, sometimes it will fit even better if put in backwards. It will move some air, look right, sound right. But won't move as much as it should, and potentially block some airflow at speed as well.

 

[SLOWnEASY]

Is your temps of 210 - 230 what the dash gauge says or is it from an IR gun?
Based on what you said my money is on the new temp sensor is probably faulty or just not the correct sensor. Maybe see if your mechanic can get some IR temp readings for you like from around the thermostat housing and see if it matches the gauge.

Any chance you can get us some pictures of the engine and from some different angles so we can see how the radiator shroud and fan and condenser sit? To post pictures you have to either link to a third party picture hosting site or subscribe to the site for $12 a year.
https://classicbroncos.com/forums/threads/how-to-upload-photos-become-a-contributor.34373/

 

[Timmy390]

New coolant sensor....Hummmm New don't mean good and old don't mean bad.

I'm guessing you have a 195 stat due to the temps you listed. I've had many a temp sensor's that I replaces with "new" that has read higher than the old one I took out. My Mach 1 for example. Mechanical reds fine......dash gauge reads high.

As mentioned...IR gun. Cheap HF will get the job done. I use mine for everything including to check my Blackstone surface temp. Also I suggest a mechanical gauge. I run them on everything that's old......Bronco, Samurai and my Mach 1.

Tim

 

[ntsqd]

^^^ That first line is my first thought.

I had a truck that needed a new radiator cap every 3-4 years. Did not matter what I bought, OEM, aftermarket, supposed OEM direct replacement. Every 3-4 years it would start running warm with no other changes. Replaced the cap after a bunch of other work that had no effect and that solved it. Next time it started running warm I went straight to the cap first, and that fixed it.
So now whenever anything starts running warm I replace the cap. I'd say 70%-75% success rate at that fixing the problem.

 

[ba123]

^^^ That first line is my first thought.

I had a truck that needed a new radiator cap every 3-4 years. Did not matter what I bought, OEM, aftermarket, supposed OEM direct replacement. Every 3-4 years it would start running warm with no other changes. Replaced the cap after a bunch of other work that had no effect and that solved it. Next time it started running warm I went straight to the cap first, and that fixed it.
So now whenever anything starts running warm I replace the cap. I'd say 70%-75% success rate at that fixing the problem.

Yeah, great thought! I recently had this issue and it was the cap. I pulled it off, cleaned it, managed to get it a little tighter wondering how it moved in the first place and thinking that was it just moved on but kept happening and cap was just faulty.

 

[nvrstuk]

So are TS's and ba123's overflows not receiving water from your caps not leaking?

Been running capless since last April on my leaking (3rd one) alum radiator. Buddy has the same brand and his is leaking also. Never above t-stat even tho water level is 4-5" below the neck all the times. Still get a little dribble from the tear between the tube and tank but this winter I will go back to copper/brass. Can idle forever or pull 5 mile long 7% grades at 75mph... guess I have more cooling "capacity" than others since I'm using so much less... Another 100 mile trip tomorrow.

 

[Chiclassics]

Its a dumb question, because things started heating drastically after service without changing fan setting , did they put right coolant? Either that or sensors are bad . only way hyou know is check engine after driving a bit. When opening the hood, if it feels like a bonfire it is indeed 210 but if it feels like a 75 at beach then its 190... without IV gun.

And I would totally change the stock fan to modern fans...this will solve your original issue at idle..

 

[Broncobowsher]

I'm still waiting to hear if they put the fan on in the right direction. As I noted, it would explain everything.

 

[Brush Hog]

Did they mess with thermostat? If so maybe they forgot to put one in or put it in upside down.

 

[Chiclassics]

Given that they changed liquids and sensors my bet is on the coolant. Or fan reversed(not sure if they need to remove for above service) the shop guys these days dont touch anything more than they need to

 

[pb4957]

Few guys have changed their thermostat to a 160. They say it's a game changer
Also adding a transmission cooler under the passenger seat.