I have a fluid leak and suspect it's coolant as the reservoir is low. From looking under the engine bay, this hose/cap looks to be saturated - anyone know what it might be?



Thanks in advance.

That looks like the vent line for your front differential if you have 4wd.

Normal level for reservoir when hot is around 1/3 full I think.
Depending on how much has been put in it.

Easy to monitor.

Make sure the level in your front diffs are at the correct level.

Thanks - will check out.

Not sure if it's related, but the top and bottom radiator hoses are also flattened or "sucked in" when the truck's not running. Should I look to replace the radiator cap? The radiator itself was replaced less than 5k miles ago.

Yes, radiator cap issue, most likely. Also make sure the vent hose to the overflow tank flows freely while you replace the cap. Use an OEM cap if possible.

As others have said, that oily hose is the front diff breather. It can sometimes burp a bit of gear oil after high speed 4WD operation. It is worth checking the front diff fluid level, but everything is probably just fine with that.

-Charlie

3bears is going through that same thing. Backflow back to the radiator is stuck somewhere along the line. Aftermarket caps sometimes work and sometimes don't. Oem ones just work.

Gang,

Sorry to say I don't think this is yet resolved.

I installed a new OEM radiator cap from the stealership and, unless the leak is residual, it seems the issue is ongoing.

I found a few drops of fluid underneath and followed it upward. Taking off the shroud, I see what appears to be coolant pooling directly below the radiator.

I plan to dry it fully and take her for another spin, though assuming it's not lingering fluid, is this indicative of a bad radiator? Having read up on the strawberry milkshake prior to purchasing the runner, I had a new OEM radiator installed a year ago at 205k miles (sitting at 213k now).

It's also worth mentioning I have a B&M 70268 cooler installed inline, which the local shop told me failed and which I disconnected from the hoses and capped off. I don't see any imperfections on the cooler and the leak persists, so I don't think that's the issue.

yes going through same thing, I think I might have solved it, or partially solved. I replaced aftermarket cap with steeler cap, replaced top hose, replaced both hoses to the over flow tank ( the one from radiator and the one inside)

its not sucking as flat as it used to , but still more than i remember my 2000 doing it.

That color could be coolant or trans fluid. You'll have to figure that one out...

Oily and fishy smelling = trans fluid
Less oily and sickly sweet smelling = coolant

Could be a leaking clamp or a punctured radiator, etc.

-Charlie

Thanks, Charlie. I have a quart of unopened ATF I can smell but I'm 99% sure it's coolant.

There aren't any hoses above the radiator showing leaks.

What's the likelihood of a punctured radiator? (other than the time I drilled into the radiator on my first car in high school while installing fog lights - true story ). The grill, tranny cooler (however small) and AC condenser all sit in front of the radiator, and the shroud covers the back.

What would be the best way to tell for certain, i.e. am I looking for a visible puncture on the surface or would it be hard/impossible to see given the fins? If the former, I could remove the cooler and condenser to get a better look from the front.

Thanks again.

Edit: I had the shop that performed the radiator replacement give it a onceover this afternoon and they're sure the fluid is ATF, not coolant.. they weren't able to identify the source of the leak and suggested hitting the front end with a proper pressure wash. It's also possible there's still fluid in the aftermarket cooler which I capped the ends of but didn't unmount - I'll probably remove it and figure out how to remount it later if it turns out to be undamaged.

Resurfacing this thread as I'm afraid this is still not resolved 😔

What I've done:

• Replaced radiator cap with OEM
• Removed tranny cooler and reconnected hoses
• Had tranny cooler pressure tested at a transmission shop - fully checked out, no leaks

I wiped everything down until there wasn't a drop of fluid anywhere, then waited a few days. Once again, there was a small puddle of fluid under the truck.

Tranny fluid seems to be pooling up at the base of the radiator where the stock cooler sits. I don't think the radiator is punctured since it's not coolant. There's no wetness anywhere above this spot nor along any hoses/clamps. The photos make it seem like it's pooling on the driver side but this is because of the driveway grading; I was previously parked in a different spot and it pooled on the other side.

Driver side (between fan shroud and radiator)


Passenger side


Is it fair to say the stock cooler is faulty? As I mentioned above, the radiator (OEM) is just over a year old and was installed by a trusted shop.

An old timers trick, throw a little talcum powder on the area you suspect and see if you can spot the leak. The hose clamp for the atf line going in or out of the radiator may have lost their clamping strength. You can cut just a little hose from the end and reposition it with a new clamp.

I doubt it's the transmission cooler in the radiator. The stock transmission cooler is surrounded by coolant except for the two fittings on the bottom that are external to the radiator. If the transmission cooler were leaking you would have a strawberry milkshake going on in your transmission. Are you sure it's transmission fluid and not coolant?

Well... I decided to verify and now I'm not sure if I might have the abhorred milkshake.



Top left is coolant, top right is ATF, and bottom is what's pooling up under the radiator. Coolant and ATF each have their characteristic smells; the fluid in question doesn't seem to have any particular smell.. does that mean the two fluids have mixed? Could it be any other fluid? FWIW, there were no other symptoms the last time I drove it a week or so ago. Shifting was butter smooth, etc. And, the radiator is brand new.

Thoughts?

The pink milkshake looks like a milkshake. Red trans fluid + Red Coolant makes pink and milky, as odd as it sounds.

That is a coolant leak. There is no other red fluid that could get on the top of the lower tank. The radiator could have been damaged in transit.

-Charlie