still runnin hot, cant figure it out

[jetfixr]

I posted a while back about my 70 c10 running hot. There was a bunch of input, and it gave me a bunch of troubleshooting tips. After a couple of weeks of messing with it, I am back again. Since then i have installed an electric fan (jeep mod) and put in a 165 degree thermostat. Today is an mild 85 degree day, I took the truck out to do some more troubleshooting. Ran it at highspeed, no grades for 10-15 min and it was running a tad over 200. Turned down a rural road with few stop signs , running about 40-45 at about 2000 rpms for about 10 min and it dropped to 190. I pulled into a parking lot, let it idle for 15 minutes and it sat at about 175. For troubleshooting i have the fan wired constantly hot. I checked to make sure the lower radiator hose wasnt collapsing, the timing is right, the temp gauge checks within a few degree of an infrared laser thermometer. The radiator is a new 3 row and should have no prob keeping up on a mild day. I am starting to question the water pump, but dont they usually leak or make noise if they are going bad?
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[davepl]

Shroud?

An electric puller fan (without a shroud) pulls air only through a very small piece of the core. Figure half of the face area of a fan is doing anything, look at that size, and compare it to how big the core actually is.

A pusher fan is probably even worse, because it's not as efficient at moving air.

Electric fans and mechanical fans both need a proper shroud in order to "force" the airflow to go through the entire core. Otherwise you're working with about the size of a heater core for actual heat transfer.

There's nothing inherently better about electric vs mechanical fans, but both need a shroud setup. I have dual electrics (with a shroud) in my 502hp Camaro and a mechanical in my 510hp Range Rover, and both cool great... but both have fair elaborately sealed shrouds.

So, now that I've preached the Gospel of the Shroud, how's your shroud?

[jetfixr]

Well I did the jeep fan mod. Quite a few guys run them with with great success. They bolt right into the stock shroud with very little room to spare around the fan. The tolerance is so close that you would swear the part is made for our trucks. The fan pulls about 25 amps and moves a whole lot of air. At idle I can take an index card, place it up against the radiator and the suction of the fan will hold it in place. I am pretty pleased with the performance of the fan. Plus at highway speeds the fan is less of a factor because you have 60 mph ram-air to cool it. It seems to cool when idling, but it seems like when the rpms rise, regardless of the 60 mph ram-air, the engine runs hot.

[Zoomin]

Is it an aluminum radiator by chance? When they have gotten hot because of some other failure, sometimes the tubes collapse which restricts coolant flow.
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[Kurt L]

i was told by a radiator company here in jacksonville fl. that you don't never want to paint your radiator fins because it reduse's the flow of air did you paint your radiator fins? that could be a cause for your running hot. i had one done by this shop, and said that i was going to paint it black and thats when he told me bout not painting them.because they hold in the heat also when you do that. just thought i'd mention that.

[Xeen]

You could try a higher flow water pump and see if that solves the problem, from your description it sounds like to me you arent getting enough circulation. You dont need a super high flow pump just something that is a little better than stock.

[Zeke's Garage]

First question is a shot in the dark, but I've seen it before.. did you happen to put on a serpentine sytem, but kept the normal rotation water pump?

Yeah, ok, probably not, so here's a more normal one:

Have you pressure tested the system? Do you have any leaks, or issues with losing coolant? If for some reason the system can't pressurize, then it will run hotter than normal, then overheat when enough coolant is lost.

Normally if the truck gets warm at speed, then it's a shroud, or airflow issue, especially if it cools off at idle or slower driving.

If you're loosing coolant, but don't see any leaks, then it could be a head gasket, and there are neat tests for checking for combustion gases in the cooling system.


Shawn

[mr48chev]

A tad over 200 at low speed isn't hot unless you have a 216 51 Chevy or a 48 ford with a flathead. Puking water out of the overflow is hot.

Getting up to 220 or 230 when in normal slow traffic is hot but I firmly think you are looking for problems that aren't even there.

[Stocker]

Originally Posted by mr48chev

A tad over 200 at low speed isn't hot unless you have a 216 51 Chevy or a 48 ford with a flathead. Puking water out of the overflow is hot.

Getting up to 220 or 230 when in normal slow traffic is hot but I firmly think you are looking for problems that aren't even there.

My thoughts also. Unpressurized water boils at 212*. Pressurized 50/50 coolant boils several degrees higher -- I've seen the numbers but don't have them in front of me.

[geezer#99]

Put a coil in the bottom rad hose and kiss your heating troubles good-bye.

[LEEVON]

Where is your temperature sending unit? My neighbor's was on the manifold near the thermostat housing. Same thing, hot on the highway and cooler at idle, which baffled me because the timing and fuel was right on, hoses weren't collapsed. I had him move it to the passenger side head, reads 175 all day now.

[Billhilly]

Interesting thread. Hey Leevon, your thread intrigues me. I had read that by the thermostat housing was a great place for an electric fan sensor (and was going to put mine in that spot) because it was right near the action (thermostat opening/closing) and would give good results. You've obviously had just the opposite result. Any idea why things improved so much when you moved back to the cylinder head?

[LEEVON]

I didn't really spend any time thinking about it, just made more sense to be in the head and I've never seen one near the thermostat but in my pea brain I'm thinking water may heat up on one side of the thermostat more quickly with greater fluctuation, and be cooler on the other side potentially allowing it to remain closed when in reality the engine itself is running a more consistent temperature. That, and naturally the coolant will be hottest at the point right before it enters the radiator (top).

I'm sure that could be dissected and up-ended LOL but it worked for my neighbor. He now enjoys his $45k street rod instead of being afraid to dive it...

[Billhilly]

Originally Posted by LEEVON

water may heat up on one side of the thermostat more quickly with greater fluctuation, and be cooler on the other side potentially allowing it to remain closed when in reality the engine itself is running a more consistent temperature. (top).

I'm sure that could be dissected and up-ended LOL but it worked for my neighbor. He now enjoys his $45k street rod instead of being afraid to dive it...

Thanks Leevon.
Hey it worked, so there you go. Interesting. Anyone else want to chip in?

[OldCreek]

Low or old trans fluid or slipping torque converter causing heat?

[jetfixr]

that is a good thought I will have to check the tranny. As far as the temp sensor it is in the head. I have revved it a few times and the radiator hose doesn't seam to be collapsing, but I may throw a coil in the lower hose just for good measure. I keep throwing parts at it, I am trying the cheaper stuff first. Looks like the next step is the water pump. Since I am going to put the time in to replace it, I may just run with a high volume pump and a high flow t-stat. I do think that 205 is excessive when driving on the flats on an 80 degree day. Especially when I have plans to put in and AC in the future.

[geezer#99]

Lower rad hose won't just collapse if you rev it up. You need to drive it down the road at 65mph, get it hot and then it will collapse. I suspected that on mine but never could catch it being collapsed until once I popped the hood real quick and it wasn't hard to see. It won't flatten right out. Jusy squeezes shut right before the water pump inlet.
Do the coil first. Save your money on the water pump.

[RustyBucket]

At higher speeds I wonder if your electric fan is blocking off a circle of your radiator the size of the fan blade. If the road speed air is, say 70mph. and the fan can only suck the air through the radiator 40mph the flow is being blocked by the fan. Maybe that would account for higher temps. at higher speed. On multi-engined aircraft if they have to shut down an engine they "feather" the blades, turn the blades in line with the airflow because a propeller windmilling is a huge amount of wind drag. Iv'e read that the drag is similar to a solid disc the size of the prop's diameter. Maybe if you shut the fan off at road speed if the temp. would go down.

[mr48chev]

Originally Posted by Stocker

My thoughts also. Unpressurized water boils at 212*. Pressurized 50/50 coolant boils several degrees higher -- I've seen the numbers but don't have them in front of me.

The boiling point raises 3 degrees for each pound of pressure. I'd have to check about what the percentage of antifreeze raises it.

One of the things I constantly see on all of the boards I am on is guys having a hemorrhage fit because the temp gauge moved past 190 or even lower and heavens forbid got up above 200 in traffic for a few seconds but dropped right back down to about two degrees above the thermostat rating as soon as the vehicle got moving again.
Hell, the Cad 500 I have waiting to go in the 71 has a 205 degree thermostat from the factory. I think I''ve got a 195 in the 71 and still tow a 5500 lb boat and trailer with it with no heat issues.

The thing is that guys drive ot vehicles for years with idiot lights or gauges that have three or four marks and a red zone for hot and the car/truck runs along at the 3/4 mark on the gauge and no one thinks anything of it but when a temp gauge that has real numbers on it gets installed and the gauge goes up above the old 40 something stovebolt or flathead range all the sudden panic sets in where no panic is due.

[long67]

Mine runs at 200 with a 190 thermastat all day on the highway. thats just the way it is. If I put in a 165 stat it would overheat.

[long67]

And I have air conditioning and I tow a travel trailer, 200 degrees.

[RHestand]

IMO I would not discount the possibility of a bad water pump.
My own personal experience: Several years ago I used to race a 71 455" GTO. For the most part it was a drag-race only car (Not lic. or street legal) so it didn't get driven much. Most of the time it would run right on the 170 deg. thermostat and every once in a while it would get very hot and boil over. (I even lost a head gasket once.) I was frustrated to the max trying to find the problem. Finally in a last resort mode, I pulled the expensive, after market alum. water-pump off, removed the back cover and found the impeller had sheered the connection to the shaft. It was positional though. You could slide the impeller forward or backward ?? on the shaft and it would become one with the shaft, push it the other way and it would free spin on the shaft. This water-pump never leaked or gave one sound to indicate it wasn't working properly. A new water-pump and all was fine! I could only chalk it up to "LIVE & LEARN"!
I hope this helps.
Ray

[RustyBucket]

Originally Posted by long67

Mine runs at 200 with a 190 thermastat all day on the highway. thats just the way it is. If I put in a 165 stat it would overheat.

Mark, I'm curious as to why it would over heat with a 165 thermostat?... just askin'. Looks like after the coolant reaches the opening temp. of the thermostat and it opens up the thermostat's done all it's gonna do except provide some restriction to slow the coolant down....

[MARKDTN]

Originally Posted by RHestand

IMO I would not discount the possibility of a bad water pump.
My own personal experience: Several years ago I used to race a 71 455" GTO. For the most part it was a drag-race only car (Not lic. or street legal) so it didn't get driven much. Most of the time it would run right on the 170 deg. thermostat and every once in a while it would get very hot and boil over. (I even lost a head gasket once.) I was frustrated to the max trying to find the problem. Finally in a last resort mode, I pulled the expensive, after market alum. water-pump off, removed the back cover and found the impeller had sheered the connection to the shaft. It was positional though. You could slide the impeller forward or backward ?? on the shaft and it would become one with the shaft, push it the other way and it would free spin on the shaft. This water-pump never leaked or gave one sound to indicate it wasn't working properly. A new water-pump and all was fine! I could only chalk it up to "LIVE & LEARN"!
I hope this helps.
Ray

Water pump was where I was about to go too. I have seen this a few times with similar symptoms.

[haysonj]

Are you sure your fan is running the right direction at speed it should run cooler unless the fan is pushing against the incoming air My fans only come on in traffic or if I turn on the AC