180° thermo is about right for us in the southwest. It typically doesn't get super cold here and regulates temperature well in the summer months. My BP 383 came with a high flow 180° thermo and it has aluminum heads. Temps generally stay below 190° ish with electric fans.
Thermostat Change
- Thread starter Ernest
- Start date
- Status
Do not drill holes in it. A hole is the same as a thermostat that can not fully close.
The idea was from people who had trouble filling a cooling system with coolant. Radiator is full and engine is full of air. A hole will let it bleed through.
All I do is fill the radiator and let the coolant slowly burble into the engine. There may be air trapped in there but a few hot to cold cycles will expel any air into the coolant recovery system. When it's cool, refill. You may have to repeat but eventually the coolant will stay at the full mark on the reservoir.
As for 160, too cold.
The idea was from people who had trouble filling a cooling system with coolant. Radiator is full and engine is full of air. A hole will let it bleed through.
All I do is fill the radiator and let the coolant slowly burble into the engine. There may be air trapped in there but a few hot to cold cycles will expel any air into the coolant recovery system. When it's cool, refill. You may have to repeat but eventually the coolant will stay at the full mark on the reservoir.
As for 160, too cold.
I dont plan on drilling any holes in this thermostat or any others i may try later on down the road, i cant anywhere with a highflow type anyway, i just had my reservations on why people were doing it, thats why i inquired within.
As far as burping the air out of the cooling system, i read else where, after flushing, raise the front end of the car and put it on jack stands so the engine is more tilted back, leave the thermostat housing open on the intake and radiator cap off, pour the antifreeze into the thermostat opening on the intake to fill the block, figure any air that gets trapped will float towards the opening in the intake, then top off the radiator and resevore, but im sure you can accomplish the same thing while keeping the car level?
As far as burping the air out of the cooling system, i read else where, after flushing, raise the front end of the car and put it on jack stands so the engine is more tilted back, leave the thermostat housing open on the intake and radiator cap off, pour the antifreeze into the thermostat opening on the intake to fill the block, figure any air that gets trapped will float towards the opening in the intake, then top off the radiator and resevore, but im sure you can accomplish the same thing while keeping the car level?
I have gotten air out of every rad I have worked on, on level ground.
You still have to drive it on inclines, to be on the safe side though lmao.
Take cap off, turn heat on, rev up every 2-3 min for 20-30, squeeze thebtop rubber hose, and if by that point it gets warm to the touch?
You are good. After that it shouldn't take more than 5-10 minutes tops to feel it warm up 😎🤟
Drilling a hole is dumb. It nets you nothing except as stated earlier, for lazy people who don't want to burp their system correctly. There's one big hole at the ready waiting to open when the engine reaches setpoint temp anyway. As with any modifications, choose them carefully to match and compliment the components that make up the system. Change things and you can inadvertently cause an imbalance and you'll chase your tail and spend money needlessly.
What's even worse if you have electric fans with a temperature sensor and don't understand that fan(s) need to come on a bit later and should not be tied to T-stat temperatures, then keep reading...
Keep in mind, the thermostat opens when the engine reaches its setpoint temp, that's when it begins to open. You could say this is the coolant minimum temperature setpoint. Say, at 180. So now, when the engine runs for a while, you may be getting temps of 205 degrees or so from the engine. The radiator/fan setup is what cools the coolant down by removing heat to reduce coolant temperatures. Engine transfers its heat to the coolant, radiator/fan works to remove heat from coolant below that what the engine is pumping out.
The water pump just keeps coolant moving to make that happen. The factory pumps are centrifugal for a reason, as are 99.9% of the aftermarket pumps you buy, regardless of drive. There is no way they'll overpower the system no matter what. Starting to clog or completely clogged radiator tubes? Dead head at a certain pressure and won't go any higher. Sure, coolant doesn't flow well, but pump still spins and moves what it can without busting something and leaving you on the side of the road.
If the system is engineered correctly, the T-stat opens at whatever temp, say 180 for this discussion. The engine is still going to pump out heat no matter what and that will vary with load and power generated. The water pump circulates water through the engine and when the T-stat reaches 180, it should start to open, maybe it's fully open by 185 or so. Cooler water from the radiator enters the engine via the water pump inlet and cools the engine while the hotter water leaves the engine via the T-stat opening to the radiator. Depending on ambient temps and if you have a sensitive coolant temp gage, you can see when the T-stat starts to open as you'll see a very slight stop, or even a dip in temp on your gage, then it starts to creep back up a bit. It happens pretty quick and some electrical gages won't even pick it up. In the meantime, the radiator and electric fan setup just sits there. Waiting. The entire system is now completely in service with the T-stat open. Radiator removes the heat as it can.
Here's where some people make a mistake, IMO, with their electric fan(s).
They pick the wrong on/off temperature switch, or misadjust the adjustable fan switch settings. There's about 40 different ways to control the electric fans, but they've got various degree setpoints on switches and what not, but the point is, I've seen switches that advertise they come ON at 185. If you install a 180 T-stat with that 185 degree on/off switch, about the time it opens is when the fan comes on and likely will never go off. WTF? You don't need this. The engine never finds its own sweet spot where the T-stat is open and the fans are off. You're trying to deny the engine's "natural" operating temperature. Don't mess with it. If the engine is in good shape, and everything else is working as it should, the engine should be happy at this point. But the fans should be set to the maximum temperature you can run, so it's not uncommon for a fan to come on at say, 220, and off at 205 or thereabouts. No sense having a war between the fan and T-stat. Note that many OEMs today usually have two fans where one comes on at a certain temp, then if it continues to rise, the second fan comes on. Or maybe a second speed for one fan. And they come on a good bit over the T-stat opening temperature. You need to choose a temperature band where the engine is happy and not overheating, the fans aren't on all the time if the A/C isn't on, and the T-stat is open. I know it's not always easy to do, but you have to let the engine find its own way for temperature equilibrium. Think of the thermal fan clutch on the belt driven fans. They lock up higher in the temperature band as well for a reason. So for this example, T-stat opens at 180 for MINIMUM coolant temp, and fan(s) come on starting at 220 for MAXIMUM coolant temp. Engine runs naturally about 210, and within that band, then it's happy, warm, and most productive. And the fans aren't running all the time.
JMO. Do what you want.
What's even worse if you have electric fans with a temperature sensor and don't understand that fan(s) need to come on a bit later and should not be tied to T-stat temperatures, then keep reading...
Keep in mind, the thermostat opens when the engine reaches its setpoint temp, that's when it begins to open. You could say this is the coolant minimum temperature setpoint. Say, at 180. So now, when the engine runs for a while, you may be getting temps of 205 degrees or so from the engine. The radiator/fan setup is what cools the coolant down by removing heat to reduce coolant temperatures. Engine transfers its heat to the coolant, radiator/fan works to remove heat from coolant below that what the engine is pumping out.
The water pump just keeps coolant moving to make that happen. The factory pumps are centrifugal for a reason, as are 99.9% of the aftermarket pumps you buy, regardless of drive. There is no way they'll overpower the system no matter what. Starting to clog or completely clogged radiator tubes? Dead head at a certain pressure and won't go any higher. Sure, coolant doesn't flow well, but pump still spins and moves what it can without busting something and leaving you on the side of the road.
If the system is engineered correctly, the T-stat opens at whatever temp, say 180 for this discussion. The engine is still going to pump out heat no matter what and that will vary with load and power generated. The water pump circulates water through the engine and when the T-stat reaches 180, it should start to open, maybe it's fully open by 185 or so. Cooler water from the radiator enters the engine via the water pump inlet and cools the engine while the hotter water leaves the engine via the T-stat opening to the radiator. Depending on ambient temps and if you have a sensitive coolant temp gage, you can see when the T-stat starts to open as you'll see a very slight stop, or even a dip in temp on your gage, then it starts to creep back up a bit. It happens pretty quick and some electrical gages won't even pick it up. In the meantime, the radiator and electric fan setup just sits there. Waiting. The entire system is now completely in service with the T-stat open. Radiator removes the heat as it can.
Here's where some people make a mistake, IMO, with their electric fan(s).
They pick the wrong on/off temperature switch, or misadjust the adjustable fan switch settings. There's about 40 different ways to control the electric fans, but they've got various degree setpoints on switches and what not, but the point is, I've seen switches that advertise they come ON at 185. If you install a 180 T-stat with that 185 degree on/off switch, about the time it opens is when the fan comes on and likely will never go off. WTF? You don't need this. The engine never finds its own sweet spot where the T-stat is open and the fans are off. You're trying to deny the engine's "natural" operating temperature. Don't mess with it. If the engine is in good shape, and everything else is working as it should, the engine should be happy at this point. But the fans should be set to the maximum temperature you can run, so it's not uncommon for a fan to come on at say, 220, and off at 205 or thereabouts. No sense having a war between the fan and T-stat. Note that many OEMs today usually have two fans where one comes on at a certain temp, then if it continues to rise, the second fan comes on. Or maybe a second speed for one fan. And they come on a good bit over the T-stat opening temperature. You need to choose a temperature band where the engine is happy and not overheating, the fans aren't on all the time if the A/C isn't on, and the T-stat is open. I know it's not always easy to do, but you have to let the engine find its own way for temperature equilibrium. Think of the thermal fan clutch on the belt driven fans. They lock up higher in the temperature band as well for a reason. So for this example, T-stat opens at 180 for MINIMUM coolant temp, and fan(s) come on starting at 220 for MAXIMUM coolant temp. Engine runs naturally about 210, and within that band, then it's happy, warm, and most productive. And the fans aren't running all the time.
JMO. Do what you want.
Some of the Robertshaw units are Robertshaw "style" units and have been modified with the holes. Original, genuine Robertshaw high flow T-stats didn't have the holes.
EDIT: At least the ones I used on Olds 455s I bought at the local NAPA didn't have the holes. I can't really say what Chevy used, but I couldn't see them being different. Speedway even says they drill holes in theirs.
Last edited:
Excellent write up 69Hurst. For some a simple system some find it complicated.
To condense it, I'll add. A fan should never run unless a thermostat is completely open. It should also never run on the highway, no fan will outperform air coming through the grill at 100km/hr.
To satisfy these two scenarios all you need is the OFF temp to be higher than the thermostat temp.
It's the thermostat's job to regulate the temp. Once it's wide open, it's done regulating. This should never happen in a good cooling system unless you come to a stop. Then the fan will turn on and pull air through the radiator that is not coming through the grille.
To condense it, I'll add. A fan should never run unless a thermostat is completely open. It should also never run on the highway, no fan will outperform air coming through the grill at 100km/hr.
To satisfy these two scenarios all you need is the OFF temp to be higher than the thermostat temp.
It's the thermostat's job to regulate the temp. Once it's wide open, it's done regulating. This should never happen in a good cooling system unless you come to a stop. Then the fan will turn on and pull air through the radiator that is not coming through the grille.
- Status
Similar threads
