Coolant gone, no leak visible??

Okay fellas. Zach here. 2001 Tacoma, V6, 4WD, 4-door, no mods, 135K miles.

I was nosing around under the hood today, in preparation for valve cover gasket replacement. (Much thanks to the writers and videographers who told how to do that, BTW.)

I glanced at the radiator overflow catch-box. Empty. Hmm. I removed the radiator cap. No fluid visible. Yikes! WTF?? I have never observed leaks under the vehicle. I DID think I was getting a whiff/smell of warm antifreeze in my nose once or twice lately, which I was curious about.

So, I took the truck to a local shop. He pressure tested, but could not produce a leak. His plan is to repeat the test in the morning when the engine is really cold.

The oil checks normal, not gray. So, hopefully not the head gasket. The water pump was replaced three and 1/2 years ago, as a preventative measure when the timing belt was replaced.

Again, I have had no leaks on the ground, and it passed the pressure test (or, at least the initial attempt.)

Thoughts or experiences appreciated.

 

Had a truck with (I think) slightly bad head gasket, would only steam a tiny bit of coolant when it got really cold out. Once truck was warm it stopped. Boiled off like a quart every 4 months. Could not get a whiff of hydrocarbons in the coolant, truck never overheated, etc. could be what you have.
I put the “nano” stop-leak that doesn’t harden in the radiator and it essentially sealed the leak. Put 15K miles on it after that with no problems.

 

Well, my friendly local mechanic pressure-tested the thing twice, and only located a tiny leak at the lower radiator hose. So, he replaced the clamp at that location. (Actually, he slid the OEM clamp back, leaving the hose undisturbed, and added a typical stainless steel hose clamp.)

I had him replace the radiator cap, but only because it was 16 years old; it wasn't leaking.

So, I dunno. I guess I'll have to just run it and see what happens.

His replacement coolant is a pale color. I assume it's Prestone. Is the Tacoma good on Prestone? I've only ever had red coolant in it.

 

You don't want to mix the green stuff with Toyota red. They don't mix well together and cause issues. All red or all green, properly diluted of course.

 

Okay, thanks Cruiserguy. There doesn't seem to be any red remaining.

 

If you have an automatic, check tranny dipstick for " strawberry milkshake". Usually an issue with 4Runners but it can happen to us. Defective washer where coolant threads into radiator corrodes causing mixture and loss of coolant which eventually bleeds out tranny vent.

 

Hmm. No, the transmission fluid appears normal, not milky.

Thanks, though.

 

My radiator is cracked on the top plastic part and it only leaks when full. Its right along a seam of the plastic mold so its not noticeable. I do smell antifreeze. but it doesnt pour off like you would think, just seeps out.

 

If you've got the original water pump, they weep fluid slowly out of the gasket material. It shows up as a white powdery crust on the bottom of the pump.

 

Seemingly mysterious 3.4 coolant loss (no exhaust detected in coolant chemical test) with an occasional odor could be from what is known as the coolant bypass tube. It's under the intake manifold and the leaking coolant tends to get trapped in the "valley" between the heads. This can not be seen with the intake manifold in place. The coolant typically cooks off (odor) unless it's a bad leak, then it spills out under a plate at the rear of the block. Very top center of 1st pic, tough to see with intake in place. The culprit is the forward end of the tube. It's a two bolt flange mount to the block (yellow arrow below). There is no gasket or o-ring just FIPG and it can degrade.
If the intake is removed it would be wise to replace the knock sensor wire harness. Old ones tend to crumble if looked at funny.

 

Toyota red coolant when diluted can look almost clear. Coolants don't change color when they get old. Like you can't tell that the coolant is old just from the color. They loose their anti-corrosion ability over time, so after a long while you could get rust color, and then you'd definitely want to change it.

Prestone makes different types of coolants for different makes and they even have a universal coolant for "all makes and models". Most likely the mechanic put the correct type in.

Coolant can evaporate from a bad/old radiator cap, so you won't notice it.

Just check your coolant level frequently and see if you are still losing it.

 

I have a similar issue. Truck seems to slowly lose coolant over an extended period of time. No noticeable signs of a HG leak. I did have me radiator crack at the top plastic cover but I replaced the radaitor. Now I noticed there is some dried coolant along the plastic radiator top where it meets the actual radiator. Can’t see an active leak but I’m thinking it’s starting to crack again and may be the issue.

 

@ Dirty Pool--
As it so happens, my intake is presently off, for valve cover gasket replacement. Here's where it stands at the moment:

 

Well, that pic is not as nice as I'd hoped, but I don't see anything white.

 

You have your upper intake off. In the pic he posted showing the coolant tube that is lower intake off, but u have to take the timing belt off to get the lower off.

 

Ahh, I see.

 

Update: I just now noticed that I do now have a leak visible on the floor, in line with the rear of the engine. There's probably several tablespoons leaked there.

I photographed it with my phone. I'll upload it when I can.

 

Okay, here we go. For this photo, I'm lying on my back under approximately the passenger floorboard, looking up. (So, sorry for the orientation.)

A significant drip from the rear of the engine can definitely be seen... How to attack it??

 

When my coolant tube that runs under the intake manifold leaked, it showed up on the back, passenger side bell housing. I followed it up to the back of the engine to the cover between the cylinder heads. I first thought it was a HG leak.

 

So was your fix as mentioned earlier, resealing the front end of that tube?