47-55.1 Having cooling issues

[my56chevytruck]

Originally Posted by _Ogre

230* is nothing, with 50/50 coolant mix you should not boil over
if your puking a little fluid it is thermal expansion only, leave it at that level, if you fill again you will puke again
50/50 coolant is good to 265*

i'd definitely go with a 185* thermostat and 16lb radiator cap

i had a 56 chevy bus with 396 truck motor that ran 250* plus in hot weather all the time
ran that way for years

I agree with Ogre, the changes I'd make include the 185 thermostat and the 16lb cap. Also, I'm not a fan of using a "pusher" fan, that's to much interference with airflow. I'd put that electric fan behind the radiator and start it up and put a piece of paper in the front of the radiator and see if it's pulling the paper to the grills, if not, the fan's running in the wrong direction. That's a wiring matter. My .02 worth.

[e015475]

"coolant is 50 50 mix....... thermostat is 160*"

Antifreeze is a relatively poor conductor of heat. Pure antifreeze will transfer about 40% less heat than pure water. A 50/50 mix will transfer roughly 20% less heat than pure water, all other things being equal. For maximum heat transfer, you'd run just water with a corrosion inhibitor, pump lubricant and maybe a wetting agent. You would have to drain and flush the radiator and put in antifreeze in the winters of course.

The amount of heat that your radiator can reject to the ambient air is a function of the temperature difference between your radiator's surface and the air going past it. When you run a 160F thermostat, you're crippling your cooling systems capacity by reducing the temperature difference between the ambient air and the radiator surface. You should be running 185F, which I believe is what GM designed for your engine.

But I suspect that pure water as coolant or ramping up the thermostat would only be useful if the cooling capacity of your radiator was good and you needed just a little more cooling capacity.

If you're satisfied that your fans, hoses, etc, are all good, and your temp still zooms way past the 160F thermostat setting, you'd have to conclude that the radiator you have can't transfer enough heat. Your cooling system is 'self adjusting' by increasing capacity by increasing the temperature difference between the outside air and the coolant by bumping coolant temp up to 220F

Your cooling system should be robust enough to run a 160F thermostat or pure antifreeze. or both, if you want.

If it were me, I'd start looking for a radiator with more cooling capacity. I'd call the tech line for Ron Davis or CR Visteon and see what they recommend for a core. I'd be inclined to buy their fan and shroud that was engineered for their radiator.

I know this isn't what you wanted to hear, but it seems to me you've eliminated everything else.

[dsraven]

all good points.
another thing to consider is that a 160 thermostat is only going to open sooner than a 185. all that will do for you is start the process of cooling sooner. once the engine heats up the coolant flow would be the same so it then depends on the rad's ability to cool the system off. another factor is the amount of coolant in the system that can work for you. a low temp stat will only keep the engine running cool if the system has the capacity to keep the system at that temp. it would be like trying to cool a warehouse to 70 deg with a window style a/c unit. the unit would run all the time and not be able to cool the warehouse because the system is not large enough to cool a warehouse. if you have a system designed to cool a warehouse and set the temp at 70 deg the system would be able to do that even under the load of having a few doors open.
the other thing that may be hampering you is possibly the ACTUAL opening temp of the stat compared to the advertised temp. I will personally not use a stat that is not in a gm box. waaaaay too many issues with the aftermarket ones. some open too early, some too late, some new ones that I have removed after a few hours of use have shown internal interference between the moving parts etc so failure was imminent right out of the chute. not worth my time to mess with an aftermarket stat anymore because of the same issues you are having. I have hung a brand new, used for a couple hours, stat in a bucket of water on the stove and found the opening temp is not correct or even close and on some the stat doesn't open fully either without binding first. the reason for the engine overheating issue-wrong opening temp and then insufficient flow. there is also the issue of too much flow through the rad so the coolant doesn't have a chance to cool off before it exits the other side. one reason for a bigger rad or one with more cores. the coolant slows down and gets to drop some heat in the process.
if it were me, I would invest in a new GM stat of the 185 temp range and go from there. look at the stat before purchase and see how much the stat can flow. even test it in a bucket of water to make sure it opens properly and at the correct temp. some are different than others in the flow area and have a larger "hole" for flow when they are open. mix the coolant to a 60% water ratio, ensure adequate air flow can enter AND exit the rad without leaking past somewhere, then try it again before going to the next step of possible rad size or core increase. really, the truck is fairly light with no load in it so a light duty rad shouldn't overheat when just cruising. that assumes adequate air flow past the fins though.
do you have a few pics of the set up that you can post? is there sufficient room between the engine and the rad for air flow to escape and if so what is the ventilation profile from there? lots of room in front of the engine but a closed area below the engine and a closed off hood area would mean there is not a ventilation profile for the escaping air to flow through. it would be like blowing air against a wall, not much flow. open a window in the wall and the flow has somewhere to go. now put a screen in the window and watch the flow rate decrease. same for vehicles. if the flow is supposed to go through the rad and then down and out the bottom (the window), but there is a whole bunch of stuff in the way (the screen), then flow rate will be compromised. I am a firefighter so flow rate and pathway during ventilation can be a big thing for us. there is no use putting a big fan in the front door and then not opening a window or a back door. the fan would just be circulating air around the front door and not flowing through the structure. we use survey tape periodically to see the flow profile and you could possibly use that technique here as well. hang a few pieces of kleenex or survey tape if you have it and see where the flow goes when the fan is turned on. look from the under side or use a camera and do this with the hood closed. try engine off, then try engine running and see if there is a difference due to belts and accy turning and possibly disrupting the air flow. a really low truck also can't flow well under the truck because the air has a longer vent profile to travel through before it can escape. running boards also can make the path longer because they add to the pathway length on a low slung truck. an ill fitting fan shroud, areas where air can bypass the rad or a lot of other coolers and a/c condensers in the area also add to the heat in the area. some guys will place a trans cooler on the frame under the truck with a scoop to catch air and/or an electric fan on that cooler. a closed in grille can also decrease the amount of available air the rad can "see" and some break up the air flow into a turbulent flow rather than a laminar flow so cooling capability can be decreased. some electric fans also have several speeds that can be used so a quick check on that may solve the issue if you find it isn't putting out what it should, is connected to the wrong speed terminal or is turning backwards. since fans are variable displacement air pumps the speed of the vehicle adds to the output of the fan. a slow moving vehicle will rely almost fully on the fan to move air across the rad, when moving the flow of air is increased due to the effect of the air charge built up in front of the vehicle "precharging" the fan. slow moving truck with possibly not a great air flow for the fan could be a compounding factor for the engine temp.
the other thing I would possibly look into is the tune of the engine to ensure the engine has the correct timing and air/fuel ratio. a lean mixture will cause the engine to run hot.

anyway, not saying there is anything poorly engineered in your system, just saying maybe a combination of things that add up to an overheated engine. in the end a new rad would be cheaper than a new engine and THEN a new rad.
just a few thoughts to hopefully fix your issue.
here is a quick read on hotrod cooling systems in case someone wants to grab a coffee
https://www.speedwaymotors.com/the-t...ng-cures/28793

[MiraclePieCo]

Desperation overheating measures:

Install auxiliary temp gauge to verify accuracy of main gauge. Use separate sender too.

Invest in a high-flow water pump.

Plumb in an auxiliary heater core to add volume to the system. It could be hidden under the truck.

Is your fan turning the right direction? Don't laugh, I've done it.

Get a bigger radiator. Yeah, it'd be a lot of work to engineer one in...

Try Water Wetter:

.

[joedoh]

Originally Posted by AD51

Well I’ve done everything imaginable and I still cannot get this thing to run cool, I have followed all the advise given here and still can’t get success. I have all the air flow passages closed up to direct all air through the radiator, I have it shrouded with an electric puller, coolant is 50 50 mix, cap is 16lb, thermostat is 160*, water pump is new, radiator is new aluminum has the two 1” flues , I have checked my timing and set it with a light exactly where it needs to be, I have flushed the system twice, it will run 220* as long as I’m moving down the road but any slow moving or grade pulling it goes up. If anyone can help with any ideas I’d appreciate it.
Posted via Mobile Device

you are running an expansion tank and not an overflow, right? if you have a side tank radand an expansion cap (two way) it will purge coolant as it warms up and pull it back in as it cools down. if you are just running an overflow, it will pull air back in.

you have your heater hoses looped? the cooling system on modern 350s does not allow for a shutoff in the heater hose or any obstruction in the heater core. the factory heater core is always passing coolant, it is simply not ducted to pass the hot air into the cabin. if you have a shutoff, or a heater that shuts off coolant flow, the coolant temp will rise when sitting still and cool when moving. I am not clear why, maybe its because heat rises and the heater lines are at the top of the engine but for whatever reason, it needs a bypass valve and not just a shutoff valve.

[AD51]

Originally Posted by joedoh

you are running an expansion tank and not an overflow, right? if you have a side tank radand an expansion cap (two way) it will purge coolant as it warms up and pull it back in as it cools down. if you are just running an overflow, it will pull air back in.

you have your heater hoses looped? the cooling system on modern 350s does not allow for a shutoff in the heater hose or any obstruction in the heater core. the factory heater core is always passing coolant, it is simply not ducted to pass the hot air into the cabin. if you have a shutoff, or a heater that shuts off coolant flow, the coolant temp will rise when sitting still and cool when moving. I am not clear why, maybe its because heat rises and the heater lines are at the top of the engine but for whatever reason, it needs a bypass valve and not just a shutoff valve.

I do not have any type of external tank just the radiator itself, I am running vintage heat and air, one of the heater hoses has an electric valve that I believe shuts off the line when you are using ac instead of heat. My radiator has no accommodations for any kind of purge tank, what can I do there? Thanks for help.
Posted via Mobile Device

[dsraven]

you will probably need a heater bypass valve in the heater loop so the coolant can still flow. here is a vac operated one for a chevy with an electric valve to run the vac on or off. dunno why it would be on the home depot page but that is what a quick search brought up, lol. you could connect it to the heater control switch or run a separate switch if you like things that way. this allows coolant to flow through the valve and back to the engine when the heat function is turned off on the heater. no hot coolant to the heater but a return flow path for the coolant.
https://www.homedepot.com/p/ACDelco-...1357/308752003
if you look at the intake gaskets on some sbc engines some have the rear ports blocked off and some are open. some have a metal plate with a small hole in it. some are universal fit with extra block off plates that you need to decide if you need the p;ates or not. confucing if you are starting from scratch. some intakes have a rear coolant cross over and some don't. some have a heater connection on the rear pass side and some don't. some guys will drill out and install flow hoses from the rear to the front so the heads stay cooler at the rear and say it increases hp and torque as proven on a dyno with the same engine to ensure apples to apples comparison.
it would be good to see a pic showing what you actually have for parts there. actually several pics of the entire system to see how things look and are set up. maybe some fresh eyes would help. sometimes you get blinded by thinking "it must be this or that" when actually it is something you assumed was all good but is slightly outta whack with the other components.

[dsraven]

https://www.centuryperformance.com/c...em-basics.html

[dsraven]

http://www.superchevy.com/how-to/148...ng-system-info


this has a few pics showing electric fans with no shrouding other than to keep fingers out. I know you have a push fan but if it has no shroud to disperse air to the entire rad then that can also factor in because at low cruising speeds the fan is the air cooling source for the rad but will only be blowing air on a smaller percentage of the rad surface.
again, a few pics to show the entire system, part by part, with the pics right side up helps.

[AD51]

Originally Posted by dsraven

http://www.superchevy.com/how-to/148...ng-system-info


this has a few pics showing electric fans with no shrouding other than to keep fingers out. I know you have a push fan but if it has no shroud to disperse air to the entire rad then that can also factor in because at low cruising speeds the fan is the air cooling source for the rad but will only be blowing air on a smaller percentage of the rad surface.
again, a few pics to show the entire system, part by part, with the pics right side up helps.

Thanks dsraven, could I not just do a test run with the heater on to see if the engine runs cooler? I haven’t done that in particular, it would allow me to see if a bypass valve would make a difference. I’ll try to get some pics up as soon as I can, thanks for your help
Posted via Mobile Device

[dsraven]

not sure what you have planned for a heater by pass but if doing it on the cheap and you wanna just try to see if flow return to the engine would help then simply disconnect the hoses at the heater end and install a cheap barbed fitting to connect the 2 hoses together. one will be 5/8 and the other 3/4 likely. you will lose some coolant when you disconnect so be aware of that and top up the rad when the system is cold. you may be able to find a fitting with the right sized fittings at a parts store if you look in the coolant flushing section.
does your intake have the rear coolant crossover built in or no? heater hose connection at the right rear or off the front? if front then usually one hose connects to the crossover on the intake manifold near the stat and draws hot coolant from there. the other connects to the water pump either on the top rear center of the pump or off the middle right side and is the suction side of the water pump so usually has the larger hose.
here is a link with a few different pics of configurations guys have used before.
when I was asking about a fan shroud on the pusher fan, be aware that a shroud would need to be able to flow air at highway speeds as well or else the fan may need to run more often even when cruising down the highway. not as easy with a pusher fan. some guys have installed rubber flap doors for better air flow at speed. when driving slow the fan pressure keeps the flaps closed but at highway speeds the ram effect opens the doors. still a restriction though.
http://67-72chevytrucks.com/vboard/s...ht=heater+hose

[joedoh]

Originally Posted by AD51

I do not have any type of external tank just the radiator itself, I am running vintage heat and air, one of the heater hoses has an electric valve that I believe shuts off the line when you are using ac instead of heat. My radiator has no accommodations for any kind of purge tank, what can I do there? Thanks for help.
Posted via Mobile Device

there isnt a tube sticking out under the rad cap? is not for overflow to the ground, it gets routed to an expansion tank. a side tank rad does not have the room to expand a little without pulling air through the system like a top tank rad does.

if you have it, that tube gets run to the bottom of a coolant tank (some people call them overflows but they arent overflows) and what happens is: when there is air in the system it collects at the high point of the system (the cap), and when the coolant expands past 16psi the bubbles get forced out into the expansion tank. there is 1/3-1/2 coolant in that tank, so when you turn the truck off, the coolant cools down and the cap opens the other way and sucks coolant back in.

if you have that tube plugged, the air cant get out. if you have it just running to the ground, it purges air correctly but since its not hooked to the tank with coolant in it, it pulls air back in. air in a cooling system is steam.


on the heater. humor me. take a loop of hose and plumb the line at the water pump to the line at the intake bypassing the heater core and that shut off valve for now. dont block either, just out then in. if this fixes your problem, you need a BYPASS valve at the heater core and not a shut off.

[dsraven]

sorry, misread what you were saying there. yes, if you haven't road tested with the heater on heat then for sure give that a try. it may show you need a bypass for the heater when the heater is on a/c so the engine has coolant flow it was designed for. if it runs l;ike it should then that was a simple fix, eh?

[dsraven]

also what Joedoh is talking about will be a must for a cross flow rad. the hose needs to be picking up from the bottom of the coolant tank or overflow tank or reservoir or whatever you wanna call it. some guys have some pretty fancy ones but ensure it is big enough for your system.

[dsraven]

once you get all the components figured out that you need and installed, fill the rad on a cold system right to the top. fill the coolant tank about a third or half. be ready for a bit of a mess. have a bucket of coolant and funnel ready to fill the rad some more. i use a funnel that fits the rad neck pretty well and also has a fitting that shuts off flow with a twist of the fitting. if the system burps some back it simply fills the funnel a bit from the bottom end but the funnel flow can be quickly shut off and the funnel removed from the rad in a hurry without losing the contents of the funnel. have a buddy start the engine and then rev it up some. when the coolant level in the rad drops immediately fill it as he keeps the engine revved up. pull the funnel and install the cap before he lets it back to idle.
run the engine to temp and watch the tank level, it should increase as the engine heats and burps into the tank. rev the engine a few times to get the water pump flowing lots, this will possibly move any air stuck in the heater core etc. later, when it cools off, the level should go down as the system draws coolant back in. when cold check the level in the rad, it should be full or very near full. top up as required.
road test to heat, then road test under load watching the temp gauge, then road test to allow system to level off temp before shutting off. allow to cool and recheck the levels. hopefully all will be good.
a bypass valve would be a great thing to have in your vintage air set up simply to allow flow and not allow the extra heat in the heater for the a/c system to deal with. the cooling system should be able to handle the loads with the heater removed from the equation. if not then possibly a larger capacity system would help.

[joedoh]

Originally Posted by dsraven

also what Joedoh is talking about will be a must for a cross flow rad. the hose needs to be picking up from the bottom of the coolant tank or overflow tank or reservoir or whatever you wanna call it. some guys have some pretty fancy ones but ensure it is big enough for your system.

I get mine at the auto parts store, like 18 dollars for an expansion tank with a mounting cage. one from a 1986-1993 s10 will also work, its squarish and has mounting tabs.


here is a 10 dollar one.

https://www.oreillyauto.com/detail/b...=603-001&pos=0

[mick53]

Have you considered a remote A/C condenser with an electric fan?