Running Hot...

[drgil]

I posted this a few weeks back still looking to find the problem. I am not too mechanically inclined but here it goes...again.

I have a 1968 Bronco with a 289. It always seems to run on the hot end (200-220 according to my gauge).

***I have replaced the radiator with a Griffin aluminum radiator/electric fan combo with 1.25" cores (I had a shroud/mechanical fan before-no difference)
***my fiberglass hood has venting for more air flow (front and back)
***I have a transmission cooler
***I have put in a flowkooler water pump with more impellers
***I have new hoses
***185 thermostat, new
***pretty sure the gauge is accurate because the electric fan kicks on at 195 (matching the gauge)


I am getting ready to check the timing, not sure if it is over bored and Im going to remove the heater core (at least by-pass it)

ANY OTHER IDEAS? What temp should I be running?

I will try to respond to the suggestions but I will be stuck at the fire station Fri/Sat.

Thanks to any help that can be offered.

 

[DirtDonk]

Just for reference (and nothing to do with answering your question), you can simply revive the original post and we can keep it going. It's usually better that way, but in this case, you did describe what you've done again, so that's a big help.

When does it run this temp? All the time, or just after a long drive? Just when running around town, or out on the open road too? Even when it's cold too, it sounds like, but is that the case?

With the hood being vented, your slow speed air flow "shouldn't" be causing it to run hot. IN theory anyway. I guess it depends on how big the vent holes are.
With the high-flow water pump, lack of flow "shouldn't" be an issue either. There is such a thing as too much flow, but since it happened before with the older pump(?), I'm guessing that's not an issue either.
Did it run this hot before the radiator swap?

Generally, it's common to run at about the rating of the thermostat. Ten or so degrees above is not out of the range of normal though.
Even though your thought of the temp gauge reading correctly based on the fan is legit, it's not absolute. You need to verify that your temp readings are exact before you sweat it too much more I would think.
Either with an infrared thermo, or a temporary mechanical gauge installed. Or one of those Mr Gasket radiator caps with the thermostat in them. I know they appear at first to be a bit gimmicky, but I think they're a nice little extra verification and a simple way to get a gauge there under the hood, where you're working.
Heck, even a turkey thermometer stuck in the filler neck of the radiator is a decent way to verify.

Good luck.

Paul

 

[drgil]

It takes a bit of driving for it to stay hot, cools down a bit when I drive then pegs out at 220 or so when I am stopped/in idle. It was running hot before the radiator swap.

Would taking out the thermostat be beneficial?

Thanks for the help...

 

[Ethansdad73]

i had a 289 in my 67 mustang and i was having issues with over heating and it was the hoses... even though they were new.. The bottom hose had a giant spring coil inside to keep it from colapsing on itself. I have the same type of hose on my bronco.

Just removing the thermostat would not really be benefical, but im in FL and im running a 160 i think and on hot days i was staying at 190... ( stock radiator, shroud, fan from bc broncos and a 302)

 

[getfuzzy]

Did you flush the cooling system? Think of the heater as another rad. leave the T- stat in to help controll the water flow. the water needs to stay in the rad to transfer the heat from the water to the rad to the air. When the temp gos up turn the heater on with the fan on high to see if the temp comes down.[it that ex rad thing] also the temp gauge built into the rad cap is a cheep way to check temp I run one all the time and it work good. Also can you smell that its running hot sounds dump but some times your nose knows.

 

[DirtDonk]

Has the engine ever been over-bored during a rebuild? Some thin cylinder walls can cause hot spots and create conditions that can't be cooled by normal means.
If it's old, and you're not the original owner, it's hard to say whether or not some coolant passages are blocked. Especially in the back of the block and going into the heads. Or an improperly installed (or the wrong one) head gasket blocking some coolant passages can do it.
How does the heater work? Could you have a big air pocket that hasn't burped out yet?

While removing the t-stat wouldn't normally be needed, or desirable in the long-term, it might at least tell you if the current one is limiting coolant flow at some level. It might be slow or late to open/close, or not opening up all the way sometimes. Happened to a member here just recently with a brand new stat.
You could run it that way, or at least test it in a pot of hot water with a kitchen thermometer for verification.

fuzzy's right about coolant flow needing to be controlled to a point and not allowed to flow too quickly through the radiator, but I don't think our engines fall prey to that as often as other issues. Maybe they do, but it might still be worth the experiment of removing the stat temporarily.

Paul

 

[DirtDonk]

And while you're spending your time optimizing your cooling system, don't forget to experiment with sealing off the radiator's perimiter to see if air-flow control is at least part of the issue.
Sealing off the top of the area between the grille and core support (where the hood latch is normally) and stuffing something in the gaps between the radiator and core support, even as a temporary test measure, might at least show whether or not it's part of the problem.

Paul

 

[BroncoJAK]

My 2 cents. Check the accuracy of the gauge with another source. Mine would run a little hot on occasion. For kicks I tried an aluminum water pump. Aluminum disapates heat better why not? I also ditched the stock shroud (really got tired of the fan hitting it during extreme wheeling) and I installed a balanced thermostat. Temps dropped 20*, and stay consistent now. More info on balanced thermostats here.
http://performanceunlimited.com/cobravalley_drivetrain/thermostat.html

 

[drgil]

I appreciate all the advice. I am not sure if the engine has been over bored. I am going to have the engine flow tested this week to see if i can narrow down the problem.

I am planning on putting in an aftermarket underdash heater/AC so should I just by pass the heater core, will that maybe cool it down?

Is there an easy way to check to see if some coolant passages are blocked? Will flow testing this answer that question ?

What temp of thermostat should I be running?

 

[BroncoJAK]

Bypassing the heater core will not let it cool better. No core= less coolant being circulated away from the hot engine.
You can flush the system easy enough, but the only real way to check for a block passage is to tear it down.
I run a 195* balanced thermostat, aluminum water pump, and a 16# radiator cap. Engine is 30 over bore, stock manifolds(headers will run hotter). Chucks 3 core all copper radiator, stock fan no shroud. Temps stay at 195* all day.

 

[drgil]

Thanks for the help. Will the flow test tell me what I want to know, at least narrow it down somewhat for me?

 

[drgil]

How accurate are those thermocaps (radiator caps)? I purchased one and noticed it said it was 140 while all my other gauges were reading 190. I now know that my gauge is pretty accurate after the flow testing (which was good) and a few other things I had done. My timing was way off and I was running VERY lean. Even though I have corrected this its still running a little hot.

 

[WARD BRONCO]

whats the front of the radiatro look like? is there a a/c condenser blocking flow? have you blowed the radiator cores out with air compresser? i had this problem with min. the condenser hampered my flow enough to cause it to overheat while under a load driving 55 mph, it very well may be an air flow issue and not water flow, start simple....

 

[bosshoff]

$20 gamble

This worked for me on a fresh engine. Try adding some Prolong or Slick 50. This dropped my engine temps 20-30 degrees.

 

[drgil]

I have no A/C in my Bronco, as far as blowing out the radiator its brand new so I am not sure blowing them out would help (I was having the same temp problems w my old radiator).

I did add something in the radiator called Wet, I assume its like prolong or slick 50, no help.

Would there be a reason the thermocap would be 50 degrees off my gauges?

Griffin Universal Radiator/Fan Combo 24” X 19 “ 1.25" cores and CFM rating for the fan of 2360 is that enough air flow for the fan?

 

[drgil]

Does anyone think an oil cooler would help?

 

[WARD BRONCO]

Yes there would, either the gauge is terribly wrong. "happened to me once" or the flow is so slow that the cool water isnt making it into the engine. make sure to run the engine with the radiator cap off. "burping the cooling system" fill as needed untill you can see that the thermostat is open. you will see the coolant cycling in the radiator. it will happen at around 180 deg or whatever your thermostat opens at. take your time and let the coolant cycle keeping the radiator full to the brim. you will get some on the ground. this will displace any air that could be in the coolant system. should take around 5 min after the thermostat opens. if the radiator never flows coolant visibly after your sure that the engine has reached operating temperature. then your thermostat isnt operating properly, causing high water temps in block and low water temps in radiator. if coolant appears to be flowing good then it is your gauge. and the rad cap gauge is correct, it will take a little longer to reach operating temp in cooler weather so be patient. i had a guge go out and it woould show me to be running 220 within 5 minutes or so of starting the engine, im laying my money on bad gauge, or possibly sticking thermostat. if its flowing water good in the radiator after reaching operating temperature its your gauge.... you will be back going in no time....DW

 

[drgil]

Thanks. I am pretty sure the gauges are correct. I have a T set up at the heater core w a 185 degree switch to turn on the electric fan and its pretty much is identical to my temp sending gauge (its at almost 190 when I hear the fan kick on).

I will try burping the system now.

 

[WARD BRONCO]

That will tell the tale.

 

[Viperwolf1]

Would there be a reason the thermocap would be 50 degrees off my gauges?

Yes, a very good reason. The gauge temp is measured at the hottest point in the cooling system. The radiator cap is at the coolest point of the system.