2002 Toyota 4Runner Engine Help

[mtbtim]

Tru dat - mine 'only' overheated to 212 once or twice for a minute or two and just as you describe, loosing coolant with no leak, puffs of smoke for a few seconds on startup and bam both heads cracked, these engines are very intolerant of excess head heat. Luck all.

212 is hot, but not crazy hot. I've had mine to 215 once and to 210 multiple times. I think it was just your engine's time. The temp I've heard is the danger zone is 230+. Once you get your engine to that level, it's a crap shoot whether your engine survives it, or it has a major fail. But, you are correct. These engines don't like to be ran too hot. The blocks aren't the problem, it's the aluminum heads. The heads are the very common failure point for these 3.4L V6 engines.

A guy I know overheated his 2UZ-FE engine in his 80 Series Land Cruiser. He had under-tightened alternator belts and one jumped off and wrapped around the fan clutch. His engine got to around 240 degrees and the radiator burst. He immediately pulled off the highway and got it towed home. I replaced the radiator for him and a week later he was getting a #1 cylinder misfire. I did a compression check of the #1 cylinder and it was very low. A leak down test showed a massive leak. The air was leaking into the crank case so I suspect the head gasket failed between the cylinder and an oil gallery. Or, the overheating hardened the piston rings and they lost their spring and were no longer getting a good seal against the cylinder wall. The result is he had a new engine installed at Yota1 Performance which was around a $10k repair bill. The moral of the story is do everything you can not to overheat your engine. General maintenance and monitoring your engine temp with an aftermarket gauge, like a scan gauge, will help you avoid a very expensive and time consuming repair.

 

[Jakeepoo3]

"People have head gasket failures and cracked heads and they never overheated the engine once". And they also have cherry red plugged cats right there. Like you said within the valuable information you provided, maintenance. I don't believe many humans understand proper maintenance of PCM inputs/stoichiometric ratio, which is why redundant cats exist in the first place, and the dealership definitely ain't doing preventative maintenance. As long as the oil gets changed here and there it's good to go haha. Oh yeah it needs gas too!

 

[jwkiss0]

Well, design and the result of that design can be very different things, right? And, what was the engineers design goal, to not seize the engine and it be a total loss? All I know is it doesn't take that much to blow a head gasket or crack a head on one of these engines. People have head gasket failures and cracked heads and they never overheated the engine once.

The OP is going to have to see what happens after he gets the new radiator swapped in. If he wants to find out the answer sooner rather than later, he will perform a compression check of all cylinders and follow that up with a leak down test of any cylinders with a low value. Or, he just drives it and sees what happens over time. A head gasket failure or cracked head doesn't always fail between the cylinder and a coolant jacket. It can also fail between the cylinder and an oil gallery, or it can fail at the seal between neighboring cylinders. With these engines, the common failure is a crack between the valves. The crack eventually migrates to a coolant jacket and coolant leaks into the combustion chamber.

Since the OP has a 2002, his engine had the superior MLS (Multi Layer Steel) head gaskets. Those are not known to fail like the older composite gaskets. If the OP's engine ends up eating coolant, it's most likely due to a cracked head.

OP, instead of just hoping you're all good, I suggest doing the compression and leak down test so you don't spend a lot of energy worrying about it.


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you made it easy enough by providing videos so I don't see why I wouldn't take your advice and perform these tests. Thank you very much!

 

[brillo_76]

That thing has ac! Fancy! Looks like we have some sh1t in common. This is my dirt truck aka "back up b1tch" I've had for twenty years. I've deleted everything out of it including AC. Not to mention every body panel [emoji23] I love the looks people give me and that it'll smoke pretty much anything that wants to give it a try.

What thing? My profile photo? ...lol heck. That's just a joke photo. My 4 runners though are mostly work beaters and I use them as service vehicles back and forth to my $$ projects.. Tetanus1 on my profile is one of my worsts one.

Sent from my SM-A536V using Tapatalk

 

[mtbtim]

you made it easy enough by providing videos so I don't see why I wouldn't take your advice and perform these tests. Thank you very much!

You're very welcome. I'm thinking good thoughts for you. Hopefully no major engine repairs will be needed.

 

[gamefreakgc]

I have definitely decided I am fixing it. Do you know the difference between the 2 different priced radiators at Toyota? One is like $125 and the other is at least double that, maybe closer to $400, I don't remember.

The only thing that gets me is why did it not want to run immediately after it overheated and why did it run rough when it finally did run? That seems like coolant got on the plugs and had to burn off?

I do know that there is an A/T and M/T radiator (A/T has transmission fluid cooler added) for the earlier years so double check the notes and descriptions. You want the one that corresponds to your transmission, that could be the difference. They also might have superseded a part number and are now offering a current radiator off another Toyota vehicle at a substantial discount as it's in production. If there's no discernable difference obviously go for the cheaper one.

There is a correlation between engine coolant temperature and idle speed. The higher the temperature the lower the idle speed so what may have happened it it saw temperatures of 230, 240 or higher temperatures and then tried to adjust the idle so it started loping. Both engines I've owned idle terribly below 600 RPM so I keep the idle speed higher than that on purpose. Under 500 RPM the engine can stall.

 

[jwkiss0]

There is a very detectable quality difference between the two. The more expensive one is an equal replacement to the original one from Japan. The more affordable one looks and feels cheaper. I've installed the more expensive one in my 2000 4runner and the cheaper one in my 1998 4runner.

Are they both still going strong? The dealer quoted me $651 for the one that’s $350ish at the Toyota online parts store. No option at all for the cheaper one.

 

[brillo_76]

I do know that there is an A/T and M/T radiator (A/T has transmission fluid cooler added) for the earlier years so double check the notes and descriptions. You want the one that corresponds to your transmission, that could be the difference. They also might have superseded a part number and are now offering a current radiator off another Toyota vehicle at a substantial discount as it's in production. If there's no discernable difference obviously go for the cheaper one.

There is a correlation between engine coolant temperature and idle speed. The higher the temperature the lower the idle speed so what may have happened it it saw temperatures of 230, 240 or higher temperatures and then tried to adjust the idle so it started loping. Both engines I've owned idle terribly below 600 RPM so I keep the idle speed higher than that on purpose. Under 500 RPM the engine can stall.

I think it's more difficult to find the [m/t] in aftermarket. I could be wrong, but I thought they quit making the [m/t], and only the [a/t] exists.

Sent from my SM-A536V using Tapatalk

 

[mtbtim]

Are they both still going strong? The dealer quoted me $651 for the one that’s $350ish at the Toyota online parts store. No option at all for the cheaper one.

The one in my 2000 is fine. I swapped out the cheaper one in my 98 for the Koyorad aluminum radiator.

 

[jwkiss0]

Well, design and the result of that design can be very different things, right? And, what was the engineers design goal, to not seize the engine and it be a total loss? All I know is it doesn't take that much to blow a head gasket or crack a head on one of these engines. People have head gasket failures and cracked heads and they never overheated the engine once.

The OP is going to have to see what happens after he gets the new radiator swapped in. If he wants to find out the answer sooner rather than later, he will perform a compression check of all cylinders and follow that up with a leak down test of any cylinders with a low value. Or, he just drives it and sees what happens over time. A head gasket failure or cracked head doesn't always fail between the cylinder and a coolant jacket. It can also fail between the cylinder and an oil gallery, or it can fail at the seal between neighboring cylinders. With these engines, the common failure is a crack between the valves. The crack eventually migrates to a coolant jacket and coolant leaks into the combustion chamber.

Since the OP has a 2002, his engine had the superior MLS (Multi Layer Steel) head gaskets. Those are not known to fail like the older composite gaskets. If the OP's engine ends up eating coolant, it's most likely due to a cracked head.

OP, instead of just hoping you're all good, I suggest doing the compression and leak down test so you don't spend a lot of energy worrying about it.


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I at least found the issue with the coolant leak. I let it run today and come up to temperature. That's when I found the steam coming out of the crack in the radiator. I let it continue to run and eventually the heat built up and it went towards the upper side of the temp gauge, but not into the red. I had the ac on to try to make it work harder and heat up. Once it heated up, I turned on the heat to try to get it to cool down. The heat never came. It continued to blow cold air for several minutes. I eventually shut it off so it didn't continue to run on the hotter side. Does this mean the thermostat wasn't working correctly?

 

[mtbtim]

I at least found the issue with the coolant leak. I let it run today and come up to temperature. That's when I found the steam coming out of the crack in the radiator. I let it continue to run and eventually the heat built up and it went towards the upper side of the temp gauge, but not into the red. I had the ac on to try to make it work harder and heat up. Once it heated up, I turned on the heat to try to get it to cool down. The heat never came. It continued to blow cold air for several minutes. I eventually shut it off so it didn't continue to run on the hotter side. Does this mean the thermostat wasn't working correctly?

Have you confirmed your heater control valve turns when you move the temperature control? You can have someone operate the lever while you watch the control valve at the firewall, near the center of the engine.

It definitely could be a thermostat issue. You're due for a radiator so just swap out the thermostat and both upper and lower radiator hoses when you do it. Make sure to get the thermostat gasket. It doesn't come with the new thermostat. Also get yourself a new radiator cap. The new radiator doesn't come with one.

 

[jwkiss0]

Have you confirmed your heater control valve turns when you move the temperature control? You can have someone operate the lever while you watch the control valve at the firewall, near the center of the engine.

It definitely could be a thermostat issue. You're due for a radiator so just swap out the thermostat and both upper and lower radiator hoses when you do it. Make sure to get the thermostat gasket. It doesn't come with the new thermostat. Also get yourself a new radiator cap. The new radiator doesn't come with one.

New radiator, cap, hoses, thermostat, coolant, and gasket ordered. Now the wait begins.

 

[jwkiss0]

Have you confirmed your heater control valve turns when you move the temperature control? You can have someone operate the lever while you watch the control valve at the firewall, near the center of the engine.

It definitely could be a thermostat issue. You're due for a radiator so just swap out the thermostat and both upper and lower radiator hoses when you do it. Make sure to get the thermostat gasket. It doesn't come with the new thermostat. Also get yourself a new radiator cap. The new radiator doesn't come with one.

Heater control valve moves along with the cable. Is there anything else to do to confirm it works?

 

[mtbtim]

Heater control valve moves along with the cable. Is there anything else to do to confirm it works?

I'm too familiar with all the components but I believe there is a blend door that needs to function properly as well.

 

[Romeo1]

Heater valve is just an open/close. It's fairly simple. They tend to corrode real bad though, because of where they are placed in the system.

Like Tim mentioned, there is a blend door. There is also a fresh air/recirculation door. Those parts are just there for the HVAC in the cab though. They don't have much input into how the engine works. The heater valve is very easy to get to inspect. It's mounted up high in the middle on the firewall.

There are a couple of different hoses that join around that heater valve also. If you're going to take the time to do a radiator swap, I would strongly encourage you to also take the time to give the system a good flush. You'll be surprised at the amount of junk you get out, especially out of the heater cores.

Like already mentioned, you will definitely want to do a new thermostat and a new radiator cap. Just get the Toyota ones. I've noticed that the Toyota thermostat is a very very different design than most of the aftermarket ones. I can't help but think that there's a reason for that.

If it was my rig, I would probably do a leak down or compression test start with just to see what's going on inside. Borescopes are really handy too if you need to take a peek without tearing everything apart. They make some really nice ones really cheap now. My 200$ twenty years ago old fiber optic one seems like hot garbage compared to all these neat digital ones they have these days.

 

[jwkiss0]

Heater valve is just an open/close. It's fairly simple. They tend to corrode real bad though, because of where they are placed in the system.

Like Tim mentioned, there is a blend door. There is also a fresh air/recirculation door. Those parts are just there for the HVAC in the cab though. They don't have much input into how the engine works. The heater valve is very easy to get to inspect. It's mounted up high in the middle on the firewall.

There are a couple of different hoses that join around that heater valve also. If you're going to take the time to do a radiator swap, I would strongly encourage you to also take the time to give the system a good flush. You'll be surprised at the amount of junk you get out, especially out of the heater cores.

Like already mentioned, you will definitely want to do a new thermostat and a new radiator cap. Just get the Toyota ones. I've noticed that the Toyota thermostat is a very very different design than most of the aftermarket ones. I can't help but think that there's a reason for that.

If it was my rig, I would probably do a leak down or compression test start with just to see what's going on inside. Borescopes are really handy too if you need to take a peek without tearing everything apart. They make some really nice ones really cheap now. My 200$ twenty years ago old fiber optic one seems like hot garbage compared to all these neat digital ones they have these days.

Small update about my ride. Got the radiator replaced and the thermostat. New hoses all around. Took it out for the first retest ride tonight. Seems to be operating ok. At first I heard a lot of water running sound which was concerning at first but I think it was the coolant circulating through the system? Ran fine, temperature stayed right in the middle. Coolant stayed between low and high like I filled it. Operationally on the surface everything looks ok. Next test is compression test and leak down test. Is there a preference in the order for those tests? I can rent a compression tester but couldn’t find a leak down tester to rent. Is there a good inexpensive one I could purchase? I appreciate all the help!

 

[Romeo1]

Small update about my ride. Got the radiator replaced and the thermostat. New hoses all around. Took it out for the first retest ride tonight. Seems to be operating ok. At first I heard a lot of water running sound which was concerning at first but I think it was the coolant circulating through the system? Ran fine, temperature stayed right in the middle. Coolant stayed between low and high like I filled it. Operationally on the surface everything looks ok. Next test is compression test and leak down test. Is there a preference in the order for those tests? I can rent a compression tester but couldn’t find a leak down tester to rent. Is there a good inexpensive one I could purchase? I appreciate all the help!

You know, just a compression test would probably be good enough. It'll tell you if you have any dead holes or not it will also tell you the difference between hot and cold.

Pull all the spark plugs out, throttle wide-open while are you crank over the engine with the starter. Obviously be careful not to start any fires. Remove the spark plugs from the wires and place the wires in a safe location.

Do all six cylinders cold and record your numbers. Then install the spark plugs and get the engine to temperature. Remove all spark plugs and repeat and record numbers.

A compression test will tell you a lot about what's going on. I wish I had bookmarked a page I found several years ago. There is a Toyota spec out there that talks about how wore out a 5vz engine is by compression test for a given elevation. I want to say 145 psi at my elevation was in the 50% range for wear.

Don't get hung up on the actual psi number. What you're looking for is the difference between hot and cold and outliers for each test.

Another very important detail here is that this is all assuming your valve timing and lash is correct. If you have any valves opening prematurely or staying open to long, it will drastically affect these results. Tim did a great video illustrating that a while back.

 

[gamefreakgc]

Small update about my ride. Got the radiator replaced and the thermostat. New hoses all around. Took it out for the first retest ride tonight. Seems to be operating ok. At first I heard a lot of water running sound which was concerning at first but I think it was the coolant circulating through the system? Ran fine, temperature stayed right in the middle. Coolant stayed between low and high like I filled it. Operationally on the surface everything looks ok. Next test is compression test and leak down test. Is there a preference in the order for those tests? I can rent a compression tester but couldn’t find a leak down tester to rent. Is there a good inexpensive one I could purchase? I appreciate all the help!

That's a great start. I still think you might be in the clear but definitely test the engine. You can borrow a coolant pressure/radiator test kit from Autozone or O'Reilly's but call ahead to confirm. They do tool rental programs if you didn't already know that. Super handy for tools you only need once and is a bit of a waste to purchase. Before you leave the store open the kit and see if the Toyota adapters fit the radiator, not all of them do. Be careful if you are driving your 4Runner to pick up the tool as you can't remove the cap if you do.

 

[jwkiss0]

That's a great start. I still think you might be in the clear but definitely test the engine. You can borrow a coolant pressure/radiator test kit from Autozone or O'Reilly's but call ahead to confirm. They do tool rental programs if you didn't already know that. Super handy for tools you only need once and is a bit of a waste to purchase. Before you leave the store open the kit and see if the Toyota adapters fit the radiator, not all of them do. Be careful if you are driving your 4Runner to pick up the tool as you can't remove the cap if you do.

Changed the oil today and there was zero sign of anything contaminating the oil. Took it for an extended ride today and up to highway speeds. No issues and the temp gauge stayed right in the middle. Going to do a compression test next and hopefully I get good results. I am slowly building confidence that it might be ok and I won’t have to pull the heads.

 

[gamefreakgc]

Changed the oil today and there was zero sign of anything contaminating the oil. Took it for an extended ride today and up to highway speeds. No issues and the temp gauge stayed right in the middle. Going to do a compression test next and hopefully I get good results. I am slowly building confidence that it might be ok and I won’t have to pull the heads.

I agree it's looking good. The oil exam is not 100% conclusive as there are times where the coolant passage of the head gasket leaks straight into the cylinder and burns off so it does not show up in the oil but usually if that's the case the temperature spikes as the system can't hold pressure. Without pressure the coolant starts to boil and causes all sorts of cooling issues.

The temperature gauge doesn't start to creep up from the middle until around 230 degrees so it may be good to read the coolant temperature from the ECU if you can. There are some simple apps like Torque and cheap bluetooth readers you can try if you have an Android device. Won't cost you more than $25 and it's very helpful. There's handheld devices you can plug in too.