Overheat
Jul 12, 2021 | 10:37 AM
#3
in addition to what jimkola asked above:
rectified block? as in a new engine block?
how many miles? how hot is it getting? did you put in a stock thermostat? FLush the system when you did all this to get the crap out of the heater core?
rectified block? as in a new engine block?
how many miles? how hot is it getting? did you put in a stock thermostat? FLush the system when you did all this to get the crap out of the heater core?
Jul 12, 2021 | 11:06 AM
#4
Registered User
Joined: Jul 2005
Posts: 2,345
Likes: 656
From: Chiloquin, OR
Bear in mind a couple things about T4Rs.
First, the temperature gauge is notoriously inaccurate. Best to get a point-n-shoot type thermometer, and verify that it IS really overheating. One of the digital thermometer you point the little red dot, and it reads out the temp of whatever the red dot is on. Best place to check is thermostat housing, once the truck has settled on the temperature it's going to be running at. Harbor Freight carries them pretty cheap.
It could be the gauge in the dash, or the sending unit. Either or. IF it's really overheating.
Second, Toyotas have a setup that is kinda bad about warming up, especially if the heater in the cab is on. They tend to go high on the temp as they warm up, but then normally come back down once the thermostat finally pops. The reason is that the "cool" water return from the heater core re-enters the main cooling system right before the thermostat. This holds the thermostat closed until the main system really gets warm. Like well above halfway on the gauge, often close to the upper white line. Once the thermostat DOES open, the system will come down to it's normal operating range. Normally, somewhere between 1/4 and 1/2, depending on the truck's gauge and sending unit.
Finally, did you burp the cooling system well, after replacing all those parts? It only takes a surprisingly small amount of air left in the system to cause it to APPEAR to be overheating. Park the truck nose high on a hill, or ramps, leave the radiator cap open to it's first closure setting, so that air and water can easily get sent to the recovery tank, and the air bubbles overboard. but the water that overflows from the radiator as it warms up isn't dribbled all over the ground. Run the truck for 20-30 min after the thermostat pops to make sure all the air bubbles out. Once the time's up, wearing heavy gloves and using a thick rag, close the radiator cap all the way tight, shut it down and let it cool completely. A couple hours at least. Verify the radiator and recovery tank are filled correctly with coolant, and you should be good to go. Just keep an eye on the level in the recovery tank for a coupe weeks.
Make sure you use the Toyota Red coolant, not the generic green coolant. The Red coolant will help prevent the differential metal corrosion these engines are prone to. They use an iron block, and aluminum heads, and the green coolant won't help prevent the corrosion a system like that is prone to, like the red is designed to do.
Let us know how things turn out!
Pat☺
First, the temperature gauge is notoriously inaccurate. Best to get a point-n-shoot type thermometer, and verify that it IS really overheating. One of the digital thermometer you point the little red dot, and it reads out the temp of whatever the red dot is on. Best place to check is thermostat housing, once the truck has settled on the temperature it's going to be running at. Harbor Freight carries them pretty cheap.
It could be the gauge in the dash, or the sending unit. Either or. IF it's really overheating.
Second, Toyotas have a setup that is kinda bad about warming up, especially if the heater in the cab is on. They tend to go high on the temp as they warm up, but then normally come back down once the thermostat finally pops. The reason is that the "cool" water return from the heater core re-enters the main cooling system right before the thermostat. This holds the thermostat closed until the main system really gets warm. Like well above halfway on the gauge, often close to the upper white line. Once the thermostat DOES open, the system will come down to it's normal operating range. Normally, somewhere between 1/4 and 1/2, depending on the truck's gauge and sending unit.
Finally, did you burp the cooling system well, after replacing all those parts? It only takes a surprisingly small amount of air left in the system to cause it to APPEAR to be overheating. Park the truck nose high on a hill, or ramps, leave the radiator cap open to it's first closure setting, so that air and water can easily get sent to the recovery tank, and the air bubbles overboard. but the water that overflows from the radiator as it warms up isn't dribbled all over the ground. Run the truck for 20-30 min after the thermostat pops to make sure all the air bubbles out. Once the time's up, wearing heavy gloves and using a thick rag, close the radiator cap all the way tight, shut it down and let it cool completely. A couple hours at least. Verify the radiator and recovery tank are filled correctly with coolant, and you should be good to go. Just keep an eye on the level in the recovery tank for a coupe weeks.
Make sure you use the Toyota Red coolant, not the generic green coolant. The Red coolant will help prevent the differential metal corrosion these engines are prone to. They use an iron block, and aluminum heads, and the green coolant won't help prevent the corrosion a system like that is prone to, like the red is designed to do.
Let us know how things turn out!
Pat☺
Jul 12, 2021 | 01:21 PM
#5
Thread Starter
Registered User
Joined: Jul 2021
Posts: 3
Likes: 0
OverHeat
Thank you Guys, complete engine overhaul was made in march, everything from rectifying block, new gasket kit, hoses, new injectors. The problem It is intermittent sometimes it runs for 2 consecutive hours with no problem. I've try to use for the most parts original Toyota parts or Toyota OE. My heater system is bypass since I don't need it. I will try some of the advice posted and share my conclusions.
Bear in mind a couple things about T4Rs.
First, the temperature gauge is notoriously inaccurate. Best to get a point-n-shoot type thermometer, and verify that it IS really overheating. One of the digital thermometer you point the little red dot, and it reads out the temp of whatever the red dot is on. Best place to check is thermostat housing, once the truck has settled on the temperature it's going to be running at. Harbor Freight carries them pretty cheap.
It could be the gauge in the dash, or the sending unit. Either or. IF it's really overheating.
Second, Toyotas have a setup that is kinda bad about warming up, especially if the heater in the cab is on. They tend to go high on the temp as they warm up, but then normally come back down once the thermostat finally pops. The reason is that the "cool" water return from the heater core re-enters the main cooling system right before the thermostat. This holds the thermostat closed until the main system really gets warm. Like well above halfway on the gauge, often close to the upper white line. Once the thermostat DOES open, the system will come down to it's normal operating range. Normally, somewhere between 1/4 and 1/2, depending on the truck's gauge and sending unit.
Finally, did you burp the cooling system well, after replacing all those parts? It only takes a surprisingly small amount of air left in the system to cause it to APPEAR to be overheating. Park the truck nose high on a hill, or ramps, leave the radiator cap open to it's first closure setting, so that air and water can easily get sent to the recovery tank, and the air bubbles overboard. but the water that overflows from the radiator as it warms up isn't dribbled all over the ground. Run the truck for 20-30 min after the thermostat pops to make sure all the air bubbles out. Once the time's up, wearing heavy gloves and using a thick rag, close the radiator cap all the way tight, shut it down and let it cool completely. A couple hours at least. Verify the radiator and recovery tank are filled correctly with coolant, and you should be good to go. Just keep an eye on the level in the recovery tank for a coupe weeks.
Make sure you use the Toyota Red coolant, not the generic green coolant. The Red coolant will help prevent the differential metal corrosion these engines are prone to. They use an iron block, and aluminum heads, and the green coolant won't help prevent the corrosion a system like that is prone to, like the red is designed to do.
Let us know how things turn out!
Pat☺
First, the temperature gauge is notoriously inaccurate. Best to get a point-n-shoot type thermometer, and verify that it IS really overheating. One of the digital thermometer you point the little red dot, and it reads out the temp of whatever the red dot is on. Best place to check is thermostat housing, once the truck has settled on the temperature it's going to be running at. Harbor Freight carries them pretty cheap.
It could be the gauge in the dash, or the sending unit. Either or. IF it's really overheating.
Second, Toyotas have a setup that is kinda bad about warming up, especially if the heater in the cab is on. They tend to go high on the temp as they warm up, but then normally come back down once the thermostat finally pops. The reason is that the "cool" water return from the heater core re-enters the main cooling system right before the thermostat. This holds the thermostat closed until the main system really gets warm. Like well above halfway on the gauge, often close to the upper white line. Once the thermostat DOES open, the system will come down to it's normal operating range. Normally, somewhere between 1/4 and 1/2, depending on the truck's gauge and sending unit.
Finally, did you burp the cooling system well, after replacing all those parts? It only takes a surprisingly small amount of air left in the system to cause it to APPEAR to be overheating. Park the truck nose high on a hill, or ramps, leave the radiator cap open to it's first closure setting, so that air and water can easily get sent to the recovery tank, and the air bubbles overboard. but the water that overflows from the radiator as it warms up isn't dribbled all over the ground. Run the truck for 20-30 min after the thermostat pops to make sure all the air bubbles out. Once the time's up, wearing heavy gloves and using a thick rag, close the radiator cap all the way tight, shut it down and let it cool completely. A couple hours at least. Verify the radiator and recovery tank are filled correctly with coolant, and you should be good to go. Just keep an eye on the level in the recovery tank for a coupe weeks.
Make sure you use the Toyota Red coolant, not the generic green coolant. The Red coolant will help prevent the differential metal corrosion these engines are prone to. They use an iron block, and aluminum heads, and the green coolant won't help prevent the corrosion a system like that is prone to, like the red is designed to do.
Let us know how things turn out!
Pat☺
Trending Topics
Jul 15, 2021 | 06:04 AM
#8
Registered User
Joined: Oct 2009
Posts: 4,831
Likes: 332
From: Northfield, Vermont
Does it happen on the highway? cruzing around town? Sitting in traffic?
Thread
Thread Starter
Forum
Replies
Last Post
2big4arunner
86-95 Trucks & 4Runners
24
Jun 15, 2012 10:29 PM
stormin94
86-95 Trucks & 4Runners
14
Nov 25, 2009 09:27 PM
