Coolant leak diagnosis - Can you help me?

[Jkysh]

Hi everyone, looking for some help on diagnosing a recent coolant leak that was discovered while traveling to my parents house this christmas break. I usually park on a rock driveway, and have not seen any leaking fluid until parked on asphalt.

I am losing next to no coolant in my tank, but the fluid that has been dripping on a piece of cardboard under my 4runner is without a doubt coolant. I can even see tiny drops forming on my front diff.

Going under the truck with a flashlight I can see a tiny drop of fluid (very tiny) and am thinking that it is coming from somewhere around the block. I am hoping I do not have a head gasket issue, but am hoping I can rule it out as I dont have any smoke or compression / idle issues.

What I am thinking, and hoping is the case is as follows: I over-aggressively filled my coolant tank on my trip home (not sure why, but I did). Can this cause too much pressure in the system, and force any "extra" coolant out of the truck wherever it can find a way to remove itself? I have not started my 4runner in the past two days, and my coolant level is right where I had left it when checked after it was totally cold the other day.

Not sure what the issue can be, but would like to have some peace of mind here. Thank you for any insights!

 

[alumarine]

If you overfilled the coolant reservoir all that would happen is when the fluid was hot it MIGHT overflow out of the tank.
It would not cause any negative issues other than a bit of spilt coolant.

You could remove the bolts from the plastic timing belt cover and pull it forward a couple of inches to see if the water pump is leaking.

 

[Jkysh]

If you overfilled the coolant reservoir all that would happen is when the fluid was hot it MIGHT overflow out of the tank.
It would not cause any negative issues other than a bit of spilt coolant.

You could remove the bolts from the plastic timing belt cover and pull it forward a couple of inches to see if the water pump is leaking.

Pulled back the timing belt cover and there is no visible leaking happening anywhere. :noidea:

I have moved the cardboard, and in the past hour or so there is not a single drop since. I am thinking the following:

I had tires put on the other day, and while it was on the lift I had the oil changed. I also asked for my diff fluids to be flushed / changed. Could a potential over fill in the front diff be causing this leak? I have been using 4wd, and recently went into 4lo and locked the rear diff in a recent snow. Im not sure if this is even possible as the fill nut should create a seal in itself.

Super slow leak, just looking for any more insight in hopes to keep my 4runner operating at its best!

 

[alumarine]

Trouble with the diff's or transfer case would not cause a coolant leak.

 

[Jkysh]

Trouble with the diff's or transfer case would not cause a coolant leak.

Im not sure its a coolant leak

Ive just cleaned off the oil pan gasket area, and tightened my oil filter a bit. There was a bit of oil looking fluid on the side of my oil pan. It has been raining and i was driving a lot before i parked it, the whole under carriage is still wet - I am hoping the excess fluid that has either leaked from the pan gasket, or has dripped from the filter is nothing other than a slowly failing pan gasket.

 

[Bijan]

Dude my shit has always had a funny coolant leak.

First it was the radiator cap. Swapped it out. It did it worse with the new one.
Now back to another one that doesn't leak, but NOW have noticed coolant leaking out of the radiator itself.

Replace radiator and see if that fixes it. OEM.

 

[alumarine]

Dude my shit has always had a funny coolant leak.

First it was the radiator cap. Swapped it out. It did it worse with the new one.
Now back to another one that doesn't leak, but NOW have noticed coolant leaking out of the radiator itself.

Replace radiator and see if that fixes it. OEM.

That's a bit extreme if it isn't the rad or it isn't even leaking coolant.
Why not replace the truck and see if that fixes it?

 

[Jkysh]

Dude my shit has always had a funny coolant leak.

First it was the radiator cap. Swapped it out. It did it worse with the new one.
Now back to another one that doesn't leak, but NOW have noticed coolant leaking out of the radiator itself.

Replace radiator and see if that fixes it. OEM.

I hear you, maybe it is just the nature of the beast. At 203k miles a drop or two of fluid every now and then seems pretty fair for perfectly reliable 4Runner.

My truck has been sitting cold and on flat surface now for about four hours. After I have wiped up the oil pan gasket area, partially tightened my filter and cleaned up any excess drip - there is not a drop of fluid on my cardboard.

As far as the radiator goes, I had it replaced with OEM when I got i. The previous owner replaced it as well, but a coolant hose outlet was stripped when threaded into the radiator, causing a persistent leak in my garage :nerd:

I will follow up on this thread with an update should the drips truly go away. I am also looking to post some pictures also, I'm loving this thing!

 

[Bijan]

That's a bit extreme if it isn't the rad or it isn't even leaking coolant.
Why not replace the truck and see if that fixes it?

What?

 

[Jkysh]

What?

I'm assuming it's internet flavored sarcasm, or perhaps arrogance.

Same manner as when I was enlightened that a coolant issue is not the derivative of a diff or transfer case "leak".

Internet thuggery :bash:
[MENTION=120787]Bijan[/MENTION] - thanks for the actual constructive insight

 

[sawguy]

If you're not sure if it's a coolant leak, maybe when they changed oil they didn't remove the skid plate and oil from the filter collected on top of the plate and is dripping.

 

[runnyrunnerton]

Do a UV dye test first with a UV flashlight. This ends most issues, and you find the leak in a hose somewhere. Buy a BIG @$$ UV flashlight off amazon for cheap. Don't skimp with the autozone junker.

If that fails. Look under the throttle body, make sure those two hoses are not leaking. Mine were. Pull the timing belt cover and make sure the water pump and in flow and outflow tubes are not leaking. Look at the gaskets connecting those two to the block. Might be a leak there.

The worst news is the water bypass pipe located under the intake leaking. Put a mirror behind your intake and look in between the valve covers there should be a diamond shaped plate with a water bypass coming out of it. If that plate is the source of your leak, the bypass pipe is cracked or leaking from a bad seal on the block and coolant is filling the cavity and leaking out through the foam seal (ask me how i know). This is not a death sentence, but you will have to remove the intake to get at it and repair the bypass tube.

Make sure you sniff your exhaust and are not burning up that much coolant.

If you smell sweet sweet coolant burning start with replacing the idle air control valve gasket. $4.00 part that you will be replacing anyway, and this cures a "slow" coolant leak and a sweet smell with good compression. some guys on pirate have a write up on it. Its in the throttle body. I never saw one diagnosed on T4R.

 

[nobb]

Most likely areas for the coolant to leak are the hoses, especially on an older truck. If you are saying the leak is around the front diff, it could be the hoses going to the oil cooler. You can reach in from around the front driver's side control arm and feel around those hoses to see if there's anything wet. Those hoses are a PITA to replace.

 

[Jkysh]

Do a UV dye test first with a UV flashlight. This ends most issues, and you find the leak in a hose somewhere. Buy a BIG @$$ UV flashlight off amazon for cheap. Don't skimp with the autozone junker.

If that fails. Look under the throttle body, make sure those two hoses are not leaking. Mine were. Pull the timing belt cover and make sure the water pump and in flow and outflow tubes are not leaking. Look at the gaskets connecting those two to the block. Might be a leak there.

The worst news is the water bypass pipe located under the intake leaking. Put a mirror behind your intake and look in between the valve covers there should be a diamond shaped plate with a water bypass coming out of it. If that plate is the source of your leak, the bypass pipe is cracked or leaking from a bad seal on the block and coolant is filling the cavity and leaking out through the foam seal (ask me how i know). This is not a death sentence, but you will have to remove the intake to get at it and repair the bypass tube.

Make sure you sniff your exhaust and are not burning up that much coolant.

If you smell sweet sweet coolant burning start with replacing the idle air control valve gasket. $4.00 part that you will be replacing anyway, and this cures a "slow" coolant leak and a sweet smell with good compression. some guys on pirate have a write up on it. Its in the throttle body. I never saw one diagnosed on T4R.

Thanks for the constructive input! I will look into getting a quality UV flashlight should the leak persist. I did clean my IAC when I first picked up my truck, as well as the throttle body and did not see any leaks when I inspected these areas as well as behind the timing belt cover yesterday. I am planning on purchasing a new IAC once it is a bit warmer out.

Ironically, it seems to have stopped for the time being. I located its initial starting point and it is coming from a silver fastener on a tube going into somewhere below my alternator. Thinking it could be going into my water pump?

On a side note - I did buy some Bars coolant stop leak but am very hesitant to put it into my engine as it is otherwise running like a top. Has any one seen any actual benefits to using this product? I do not want to create a mountain out of a mole hill as I am truly only losing a teaspoon or fluid over the course of a few days when this leaks decides to rear its head...

 

[runnyrunnerton]

The problem with stop leak is it treats the entire system. Your putting a coagulant in a stream that's meant to run free and smooth. You wouldn't inject flour into your right arm to stop a cut you got shaving. I can say based on my previous experience, they work great for super small leaks, however you spend the next six months wondering if the $10 bottle of sticky crap is going to kill a critical component. According to the internet it will kill something. I've never had it kill one of my components, but I swore the stuff off when i treated my cooling system, then found the leak later. Cant flush out something designed to stick to the walls. Not worth the worry, just find the leak/fault and swap the part out, you will sleep better. Get yourself a field service manual, that makes these things much simpler to pull apart.