[1991 4Runner] Bottom of the radiator leaks when pressurized
#1
[1991 4Runner] Bottom of the radiator leaks when pressurized
[1991 4Runner V6 4WD 5-Speed]
Hey guys, long time lurker here and although I've solved a lot of prior problems just by browsing the forums, I have a question that I've yet to find an answer to.
I recently repaired a leak in the cooling system near the rear-top of the engine compartment when a hose developed a crack and sprayed coolant when prodded or put under pressure.
Having fixed *that* leak, I've since discovered another on the bottom of the radiator. This time, the leak only occurs once the engine has heated up and the cooling system has pressurized. As far as I can tell, the coolant appears to be leaking from the seal between the main radiator grill and the bottom manifold that feeds from the engine into the radiator.
I believe the radiator was replaced with an aftermarket product, as the bottom manifold has ports for both a manual and an automatic engine.
My question: is there anything else that could be causing the leak or am I doomed to re-replace the radiator?
Another site (specifics escape me) mentions that there might be an air bubble trapped in the system, but I wanted to get more information before proceeding.
This is my first post. I've read through all the FAQs, but if I've missed anything or left out necessary information, please let me know. Thanks!
Hey guys, long time lurker here and although I've solved a lot of prior problems just by browsing the forums, I have a question that I've yet to find an answer to.
I recently repaired a leak in the cooling system near the rear-top of the engine compartment when a hose developed a crack and sprayed coolant when prodded or put under pressure.
Having fixed *that* leak, I've since discovered another on the bottom of the radiator. This time, the leak only occurs once the engine has heated up and the cooling system has pressurized. As far as I can tell, the coolant appears to be leaking from the seal between the main radiator grill and the bottom manifold that feeds from the engine into the radiator.
I believe the radiator was replaced with an aftermarket product, as the bottom manifold has ports for both a manual and an automatic engine.
My question: is there anything else that could be causing the leak or am I doomed to re-replace the radiator?
Another site (specifics escape me) mentions that there might be an air bubble trapped in the system, but I wanted to get more information before proceeding.
This is my first post. I've read through all the FAQs, but if I've missed anything or left out necessary information, please let me know. Thanks!
#2
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Time for a new radiator or, depending on the radiator, having it repaired by a radiator shop. Do not use any radiator stop seal products unless you want more problems later on.
A air bubble would not cause a leak like that.
The ports on the bottom of the radiator are used for automatic transmissions, not manuals. Also, coolant flows in the radiator at the top and back to the engine out the bottom on the 3.4L. I know nothing on the 3.0L at all.
A air bubble would not cause a leak like that.
The ports on the bottom of the radiator are used for automatic transmissions, not manuals. Also, coolant flows in the radiator at the top and back to the engine out the bottom on the 3.4L. I know nothing on the 3.0L at all.
Last edited by rworegon; 01-27-2015 at 12:04 PM.
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Lol. Oops, my bad! I had 3.4l on the brain....that's what I get for reading too quickly. Can't say I know anything about the 3.0L.
Last edited by rworegon; 01-27-2015 at 12:02 PM.
#7
I talked to a very good custom radiator builder recently. He said the aftermarket copper radiators are junk because they use thin copper and low lead solder. He suggested getting the plastic/aluminum type at $160 as they would last longer, or he could custom build a copper type at $300 that is better than aftermarket. My Modine radiator started falling apart after 2 years.
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#8
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I think all conventional rads flow from the bottom of the rad, through the lower rad hose through the block and out the upper rad hose to the rad, otherwise they would potentially suck air from the top of the rad.
Last edited by Marc; 01-27-2015 at 07:20 AM.
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Before you replace the radiator, remove enough trim parts so you can actually see the leak. I thought I had a broken solder connection on the lower outlet tube, but it turned out to be leaking from the lower radiator hose-radiator connection. Replacing the factory spring-type clamp with a cheap standard worm-screw clamp fixed it for me.
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Coolant flows into the radiator at the top, and out at the bottom, as the previous poster said.
From the FSM for the 3VZE:
RADIATOR
The radiator, mounted at the front of vehicle, consists of upper and lower tanks and a core connecting
the two tanks.
The core contains many tubes through which engine coolant flows from the upper tank to the lower
tank: Air passing over the radiator fins cools the heated engine coolant flowing through the radiator.
The upper tank has an inlet for engine coolant from the water jacket and it has a filler inlet. It also
has a hose attached through which excess engine coolant or steam can flow. The lower tank has
an outlet for the engine coolant and a drain cock. Automatic transmission models include an automatic
transmission fluid cooler.
From the FSM for the 3VZE:
RADIATOR
The radiator, mounted at the front of vehicle, consists of upper and lower tanks and a core connecting
the two tanks.
The core contains many tubes through which engine coolant flows from the upper tank to the lower
tank: Air passing over the radiator fins cools the heated engine coolant flowing through the radiator.
The upper tank has an inlet for engine coolant from the water jacket and it has a filler inlet. It also
has a hose attached through which excess engine coolant or steam can flow. The lower tank has
an outlet for the engine coolant and a drain cock. Automatic transmission models include an automatic
transmission fluid cooler.
#11
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Coolant flows into the radiator at the top, and out at the bottom, as the previous poster said.
From the FSM for the 3VZE:
RADIATOR
The radiator, mounted at the front of vehicle, consists of upper and lower tanks and a core connecting
the two tanks.
The core contains many tubes through which engine coolant flows from the upper tank to the lower
tank: Air passing over the radiator fins cools the heated engine coolant flowing through the radiator.
The upper tank has an inlet for engine coolant from the water jacket and it has a filler inlet. It also
has a hose attached through which excess engine coolant or steam can flow. The lower tank has
an outlet for the engine coolant and a drain cock. Automatic transmission models include an automatic
transmission fluid cooler.
From the FSM for the 3VZE:
RADIATOR
The radiator, mounted at the front of vehicle, consists of upper and lower tanks and a core connecting
the two tanks.
The core contains many tubes through which engine coolant flows from the upper tank to the lower
tank: Air passing over the radiator fins cools the heated engine coolant flowing through the radiator.
The upper tank has an inlet for engine coolant from the water jacket and it has a filler inlet. It also
has a hose attached through which excess engine coolant or steam can flow. The lower tank has
an outlet for the engine coolant and a drain cock. Automatic transmission models include an automatic
transmission fluid cooler.
It is a certainty that the hot water enters the bottom of the radiator on 3vze engines.
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Short of pulling the upper radiator hose and running the engine, is there a way to figure this out?
#13
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All you have to do is look at the position of the thermostat. When it opens, the coolant is permitted to flow out.
The 3vze thermostat is positioned at the bottom hose connection.
Conventional cooling systems that flow the hot coolant out the top have their thermostat positioned at the top hose connection.
I don't see how the 3vze thermostat could ever open if the hot flow is indeed from the top of the radiator.
The 3vze thermostat is positioned at the bottom hose connection.
Conventional cooling systems that flow the hot coolant out the top have their thermostat positioned at the top hose connection.
I don't see how the 3vze thermostat could ever open if the hot flow is indeed from the top of the radiator.
Last edited by millball; 01-27-2015 at 08:50 AM.
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I find it hard to believe that anyone would design an automotive cooling system where the coolant was pulled from the top tank of the radiator. That would only work if the radiator was always completely filled. If the coolant level was down even just to the top of the radiator cores, the water pump would be pumping huge air bubbles into the block, which as we know isn't good.
I'll take a look at my vehicle when I get home - I'm not yet convinced the manual is wrong.
I'll take a look at my vehicle when I get home - I'm not yet convinced the manual is wrong.
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So I searched the internet. And the answer is: just about 50% are sure it's one way, 50% are sure it's the other way, and both groups think the others are idiots.
This site http://www.k20a.org/forum/showthread.php?t=78154 is about Honda/Acura K engines which also have the thermostat on the lower hose side. The Honda manual is also clear: coolant flows from top to bottom to thermostat to pump.
This site http://www.pbase.com/aw11mr2/image/109957581 has the cooling system of a MK1 disassembled; the thermostat is not right next to the pump, but it is also on the exit-from-radiator side.
Millball has the right idea; this is a job for actual experimentation. I hope an IR sensor works; I might try it myself.
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It's interesting that there are so many variations on such a basic system that's been in existence for over 100 years. You'd think by now that one "best" design would have completely taken over.
#18
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Well, the IR thermometer readings don't lie. It is clear that I was wrong.
The hot coolant does indeed discharge into the radiator top. I measured about 170f
at the top tank and about 90f at the bottom, after engine warmup.
It must be that the thermostat heat pellet is protected from the incoming cooled coolant, as scope103 suggested.
I was wrong, wrong, wrong about this, but it was an honest mistake
The hot coolant does indeed discharge into the radiator top. I measured about 170f
at the top tank and about 90f at the bottom, after engine warmup.
It must be that the thermostat heat pellet is protected from the incoming cooled coolant, as scope103 suggested.
I was wrong, wrong, wrong about this, but it was an honest mistake
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Millball beat me to it (hey, it was his idea!) I was curious enough to run the same test this afternoon. The truck is garaged in the winter, so I parked it on the driveway to get it to ambient temperature. As you can see, we are just getting hammered by Old Man Winter here in Northern California. ;^)
time Lower Upper time in min:sec, temps in °F, measured on hoses
0:00 67 69
1:00 60 64
2:00 63 73
3:00 65 81
4:00 68 85
5:00 77 94
--------------------- idle dropped to 850 at 5:00, so truck now "warmed up"
6:00 71 99
7:00 73 112
8:00 87 121
9:00 83 133
So I got the same result as Millball. And like Millball, I'm now convinced the FSM (on this point, anyway) is correct.
Note how the temperature at the lower radiator hose actually dropped at 6:00, possibly because the thermostat opened allowing cold water to drain out of the radiator into the hose. (But don't go nuts; it's hard to get an accurate temperature with an IR thermometer.)
time Lower Upper time in min:sec, temps in °F, measured on hoses
0:00 67 69
1:00 60 64
2:00 63 73
3:00 65 81
4:00 68 85
5:00 77 94
--------------------- idle dropped to 850 at 5:00, so truck now "warmed up"
6:00 71 99
7:00 73 112
8:00 87 121
9:00 83 133
So I got the same result as Millball. And like Millball, I'm now convinced the FSM (on this point, anyway) is correct.
Note how the temperature at the lower radiator hose actually dropped at 6:00, possibly because the thermostat opened allowing cold water to drain out of the radiator into the hose. (But don't go nuts; it's hard to get an accurate temperature with an IR thermometer.)
Last edited by scope103; 01-27-2015 at 08:44 PM.