Radiator overflow, overflowing (12 Viewers)

[TheITGuy]

I've noticed my rig typically gurgles a bit after a drive on a hot day, but I don't have any overheating problems (far as I know) or any coolant leaks.

Reading through these posts, it sounds like the only time you've gotten the IR gun out was on a morning run when outside temps were in the 70s. Someone can correct me if I'm wrong, but the readings you shared didn't look to be too far off of normal operating range. I'd be curious to know what type of readings you get after a drive in the 90s?

Also, I would check your hose clamps and make sure they are all tight, especially around the overflow since that seems to be where you are losing coolant. Last time I had a leak, it was just a clamp that wasn't quite tight enough.

 

[charliemeyer007]

Find a steep ramp - park on it - remove the radiator cap, top off fluid - run engine for a while until you see serging/fluctuation in the level of the fluid - the thermostat is opening/closing. Clamp off one of the heater lines to the front heater for a few minutes - this will force flow to rear heater; move clamp to rear heater hose. Your cooling system should be bubble free. Put on cap, fill tank like 1/2 way. As the rig fully heats up, coolant will be pushed out of rad into tank. When it cools back down, fluid will be sucked back into rad if everything is working correctly.

 

[65swb45]

Returned your voicemail

 

[wchevron]

Got the new blade/fan clutch installed. Thanks @65swb45. Took it out yesterday. Still having the same issue. Ran it for 2-3 min just to make sure the fan blade was running smoothly. It was. Took about a 25 min ride to a friends. After 15 min the engine temp gauge had climbed back up the hash mark to the left of the H. Right where it was before I changed the old blade out. It was all highway driving about 60mph at 3000 rpm, steady. Once I got off the highway, its about 5 min to my friends. In that 5 min, the gauge came down to just below the hash mark. Driving home that night, same thing. Temps slowly climb after 15 min, then stay right at or just over the hash mark. Didn't have anything with me to check the temps, at the time.
I also replaced the radiator cap this past week, just to see if that also helped along with the fan clutch.

Wondering what my next step should be? Should I pull out the thermostat and test it?

I don't remember having this issue last summer or beginning of this summer. Seems to happen now everytime I drive it. After 15 min or so it gets up to the hash mark and just stays there the rest of the drive.

 

[Skreddy]

Did you add anymore coolant to the overflow; NOT to the radiator for the drive?
I would continue adding to the low line on the overflow bottle until its stops sucking it in. Still probably have air in the system and that’s why it sucked up what was in there. But if you don’t keep putting coolant in there, every time it cools, it sucks air back in instead of coolant. I’d even go as far as filling it midway or to the high line to ensure there’s plenty of coolant to suck back in as it cools.

 

[wchevron]

I did add coolant to the overflow a while back, about halfway between low and high fill lines. Have checked it a couple times since and it always seems to be at the same level I filled it to.

Someone mentioned above to park it on a steep hill, pull off the cap and run it for a bit. Tried that in the driveway. Jacked up the front end high as I could and ran the truck for 5 min. Maybe not long enough? The coolant level would fluctuate. Would over flow a bit, then drop, then overflow a bit, then drop back down. When it overflowed it wasn't a lot, could grab most of it with rag. To be honest, not really sure if any air came out or if I did the whole process wrong. Once I stopped it and dropped the truck back down. The coolant level didn't appear to have dropped much at all so I didn't lose that much when it overflowed.

 

[Skreddy]

Going back to earlier posts, I wouldn’t be so sure that it is actually getting too hot (though getting rid of that flex fan was worth the thread!). Your IR gun temp readings looked fine and who knows if the sending unit and gauge match, or condition of sending unit since you haven’t had it too long.
Being at that top mark but not to the H isn’t nice to see but, according to the FSM, it’s not overheating.
I’d try to get more temp gun readings: top tank of radiator, thermostat housing, heater valve at rear of head, etc. Then decide if it’s really getting hot or not.

 

[charliemeyer007]

With the cap off, engine running the level of the coolant will surge up and down some as the thermostat open and closes.

The cap needs to be the highest point in the cooling system by a fair amount - jacking the front end up several feet would do that or find a steep ramp

Thermostats are cheap, put in a 165 degree one instead of a 180.

Stock gauges are crud at best, 40+ year old gauges don't improve on their own. Check with a laser thermometer.

Maybe rot out the block cooling system with a chemical treatment and have a shop do the radiator. Maybe some PO put in a ton od stop leak and passages are clogged.

Check the timing retarded will run hot so does too much advance - but it should ping like hell

 

[knuckle47]

If it means anything, my 75 F2 block runs between 189 and 194 religiously when warmed up summertime driving.

Confirmed all of this with the IR gun and the Holley sniper handheld display if it moves more than 3* in my case it’s unusual. My timing runs at 12° on start up and advances accordingly. Again confirmed with the sniper handheld display and timing light.
It seems as though you’re really not overheating just running a bit hot. Do you believe your radiator is clean and clear flowing?
Where are you at the stage of the game?

You’ve certainly got some time invested here so far, wondering where it’s at now.

 

[70fj40]

If I were in your shoes at this point my next step would be verify I have no leaks and all hoses are good shape and clamps are tight. Replace my thermostat, flush the cooling system, refill, make sure I burp air out then call it good.

 

[65swb45]

I agree with @charliemeyer007 : take some readings with an IR gun and, if the temps warrant it, put in a lower temperature thermostat.

 

[wchevron]

Thanks all. Will try to run it a bit the next couple of days and take some temps with the gun. When in the engine, to add the fan/clutch, was also under the truck quite a bit, kept dropping the nuts to hold the fan on. Didn't see any coolant leaks so think all the hoses are tight and in good shape.
Last year when I bought it, I pulled the heater to refurbish. There was a lot of crud in the heater coil. Had one of the guys at work drain the coolant for me before I pulled the heater. He remarked the coolant was pretty clean. With the heater out, bypassed it and just ran water in the engine all summer. At end of the summer, drained the water and reinstalled the heater, then filled with new anitfreeze. So it's been filled/drained 2x in the past year. I'm assuming the system is pretty clean. Didn't notice a bunch of crud when we dumped the water to put the heater back in.

Looking around the engine, when installing the fan clutch, noticed either there isn't a gasket at the thermostat housing or there is a gasket but the PO also used some sort of gasket sealant. You can see the sealant on the outside of the housing so the PO was in there at some point to either check the thermostat or replace it.

 

[wchevron]

Just so I'm understanding the coolant system correctly. Coolant circulates through the engine until it reaches the thermostat temp (say 180*). Once the stat senses the coolant is at 180*, it opens and now flows the coolant through the radiator, which helps reduce or maintain the coolant temp so the truck doesn't overheat? If i replace the stat with a 165* stat, that process will happen earlier, at 165* vs 180* which will engage the radiator sooner and also help keep the engine temp down? Sorry, was never much of a car guy so all this is new to me.

 

[pb4ugo]

Changing the tstat temp range can change the general operating temp. Keep in mind the water capacity is limited, but is sized to cool the engine. The tstat regulates the water flow to keep the temps at its' rated temp or will remain open if the temps are above its' rated temp. The fan clutch has a tstat on the front of it and senses the air temp going thru the radiator. If the temps are high, probably a little above the boiling point, the fan clutch will lock up and engaged the fan to pull more air thru the rad until the temps drop.

As others have said stk gauges aren't the most accurate. You can try to determine your installed tstat temp by starting the engine cold and monitor the upper rad hose with your hand. When the hose turns hot the tstat opened, use your IR gun on the tstat housing and check it's temp. That will probably be close, or you pull it and look. I run and sbc and run a 160* tstat.

 

[brian]

Clean/replace the sending unit

 

[wchevron]

Finally got out tonight to get some temp readings. Not really sure what they are telling me. I did pick up a 160* stat and a new sending unit just in case.

With the temp gauge sticking straight up, about center of the hash marks.
Top of thermostat housing 183*
Top header of the radiator 183*
Top of radiator, about 1" down from the top header 163*
Middle of radiator, right below the Toyota. 130*
Bottom of radiator. 110*

When the temp gauge was right at the hash mark close to the H
Top of thermostat housing 215"
Top header of the radiator 202
Top of radiator, about 1" down from the top header 177*
Held the temp gun down and ran it along the top of the radiator from the driver side to passenger side. Temps went from 177*-120*-176*-170*
Did the same along the middle right below the Toyota badge. Ran from driver to passenger side. Temps ranged in the 90* all the way across.
Bottom of radiator. Also from driver to passenger. Temps ranged from 130* to 97*
Also shot the radiator hose at the bottom of the radiator back to the engine. 165*

Then one last time when i got home. This was about 10 minutes after the previous temp readings. Gauge was reading just below the right hash mark. This was as soon as I shut the truck off
Top of thermostat housing 210*
Top header of the radiator 197
Range across top of the radiator. Driver to passenger again. 188 to 206*
Range across middle of radiator. Driver to passenger again. 155-160*
Range across bottom of the radiator. Driver to passenger. 136-123*

 

[SteveH]

Observation: Your aftermarket fan is a lot smaller than the shroud, which doesn't help with air flow.

 

[pb4ugo]

Finally got out tonight to get some temp readings. Not really sure what they are telling me. I did pick up a 160* stat and a new sending unit just in case.

With the temp gauge sticking straight up, about center of the hash marks.
Top of thermostat housing 183*
Top header of the radiator 183*
Top of radiator, about 1" down from the top header 163*
Middle of radiator, right below the Toyota. 130*
Bottom of radiator. 110*

When the temp gauge was right at the hash mark close to the H
Top of thermostat housing 215"
Top header of the radiator 202
Top of radiator, about 1" down from the top header 177*
Held the temp gun down and ran it along the top of the radiator from the driver side to passenger side. Temps went from 177*-120*-176*-170*
Did the same along the middle right below the Toyota badge. Ran from driver to passenger side. Temps ranged in the 90* all the way across.
Bottom of radiator. Also from driver to passenger. Temps ranged from 130* to 97*
Also shot the radiator hose at the bottom of the radiator back to the engine. 165*

Then one last time when i got home. This was about 10 minutes after the previous temp readings. Gauge was reading just below the right hash mark. This was as soon as I shut the truck off
Top of thermostat housing 210*
Top header of the radiator 197
Range across top of the radiator. Driver to passenger again. 188 to 206*
Range across middle of radiator. Driver to passenger again. 155-160*
Range across bottom of the radiator. Driver to passenger. 136-123*

I don't really see any issues with what you describe. You might consider installing the 160* Tsat. I'd guess the one. that's in there is close to 195*, and is probably why you're seeing temps around 200*.

 

[wchevron]

Observation: Your aftermarket fan is a lot smaller than the shroud, which doesn't help with air flow.

Just installed a correct sized fan/fan clutch so I don't think that is the issue.

Going to try the 160* stat and new sending unit. Was also thinking of giving it a flush. When I was running the temp gun along the radiator, there would be a spot or two that would be 20-30* off the rest in the same elevation. Thinking maybe there is some partial blockage in some of the radiator passages When I pulled the heater last summer, there was a lot of crud in the heater core.

 

[BullHab]

Added some antifreeze to the overflow tank. Another hot/humid day today so will keep an eye on it. I have noticed before, when the temp gauge gets up to that line before the H, If I end up off the highway and on some side roads for a bit and going slower and the engine rpm are down, the gauge will drop down fairly quickly to almost the center of the gauge.

That acts normal. What rpm are you running down the freeway? What is your gearing, 4.10 or 3.73?