Hey guys, have a weird problem here. There seems to be a black hole somewhere inside my engine block that's swallowing all my coolant. I drive 30 miles each way to school every day and when i check my coolant the next day in the radiator it's about an inch and half low. Easy answer, right? "Check for leaks, Inferno," "You have a bad head gasket, dude." Well, it's not that simple. NO drips on the ground. Everything in the engine bay looks clean. No smoke or sweet smell from exhaust. Good, even compression across all cylinders (5000 miles on complete engine rebuild). Block tester says no combustion gasses in coolant system. No overheating, perfect temperature. Can't think of what else to report on, but it's going through coolant pretty darn fast. If i fill the reservoir that even gets emptied. Any suggestions on where to look next?

 

Pressure test your coolant system?

 

Is it a 22re?

 

this.

 

Sorry guys, yeah, this is on my 4runner. 87' 22re manual transmission. Anybody know where to rent a tool to pressurize the coolant system?

 

The Pep Boys near me had one to rent for $105. If you have a Harbor Freight near you, they have one on sale right now for $80. Got mine for $65 with a 20% off coupon.

 

Radiator cap bad so it's venting at too low a pressure?
Hairline crack on radiator above coolant fluid level so steam escapes but no fluid comes out?

Sometimes those scientific tests would not reveal problems.

I once had a hairline leak on radiator of my XTerra. It was above coolant level so when shop pressurized the system there was no fluid leak, and pressure check did not reveal anything. It was during my old-school visual inspection that I saw sign of steam exposure around the hairline crack.

Hopefully, a pressure test would expose your problem.

A quick and simple test for HG problem:
with engine cold (first thing in the morning), take radiator cap off
Start engine
Coolant welling over/over-flowing or bubbles while engine is still cool means cooling system is being pressurized by compression. I know nothing else that would pressurize cooling system while engine is still cool.

(Overheating, of course, will cause coolant to boil over and cause high pressure)

 

Is there a chocolate milky substance on the inside if the oil cap? If so u have a crack in a water jacket somewhere. Could be head gasket as well.

 

Check for a hairline crack where the hose connects to the radiator on top. I have had that twice. My radiator shop seals and pressureize mine and submerses it in a tank of water. It will eliminate the radiator. If you go that far, have them to flush the radiator as well. It will have a lot of gunk in it if it orginal.

 

No mixing of coolant and oil whatsoever. All coolant hoses are new, clamps are all tight, and none of them are wet. Radiator cap also new and passed pressure test. Coolant doesn't move in radiator when engine is cold and no bubbles whatsoever. This is starting to drive me nuts! I'll try and do a pressure test tomorrow and update.

 

Sears used to have a coolant pressure test kit for about $50, which is way less than Harbor Freight. ALso, most of HF's stuff is crap~

 

4 cyl are bad about electrollisis eating the head. then they spray antifreeze out the exhaust in small amounts. Will get larger as time marches on. No mixing and usually run perfect.

 

Leak at the rear seat heater... Aka under your center console.

There is another heater core in there with 2 hoses.

 

I'm not sure if it's the same where you are, but here, the local oil change shops do a free pressure test of your cooling system including pressure testing your rad cap.

 

I think i got it figured out! I was WAY to cheap to buy a coolant pressure tester so i built my own (4 bucks!) and pressure tested the system. I found a miniscule pinhead leak in the front of the top tank of the radiator. I think it was just slow enough that the coolant would evaporate as it was coming out. There was also a pinhole leak in one of the heater hoses that would drip right onto the exhaust pipe, also evaporating. That's why i didn't have any drops and couldn't find any leaks. I pulled the radiator and applied epoxy where the hole was, i'm hoping that it will hold. The hole is so small that after cleaning the area I can't even find the hole any more. I'll make a thread on how i built my pressure tester and update tomorrow after another pressure test.

 

Well, that wasn't it! Still losing coolant at an alarming rate. About a gallon every few hundred miles. With that much coolant loss you'd think it would be easy to find. Again to recap-
1-No abnormal smoke from exhaust. It's cold outside so there's condensation vapor, but nothing abnormal and absolutely no coolant smell. I've smelled it before many times and would recognize it.
2-No obvious leaks. Engine, transmission, and entire engine compartment is dry as a bone. No drips under the truck after sitting. I've pressurized the system and let it sit for several hours, no leaks.
3-Not the head gasket. Block test rules this out for sure, but also no symptoms of it. No overheating, loss of power, smoke, etc. Less than 10,000 miles on new engine I built myself. Head was resurfaced properly and torqued properly with a quality head gasket.

I'm REALLY at a loss as to where it's going. It's a significant amount of coolant, which worries me. Anyone have any ideas?

 

It's either burning off or leaking. You just have to narrow down the possible causes.

Do you notice any smoke coming from the engine bay when the engine gets hot? The U-shaped hose on the back of the engine is the culprit for some (has been on both 3VZE's I've worked on), it will leak but it drips directly onto the exhaust. Take a flashlight and look behind the engine, it'll be obvious if it is.

If you're absolutely sure it's not leaking in the engine bay, it could be that your heater core is leaking in your cab and exiting out somewhere else.

You might have a hose hooked up wrong, such as a coolant line accidentally hooked up at the wrong spot at the air chamber and allowing coolant to pour directly into the combustion chamber. Something like that would not be very noticeable since it would only do it once the engine was warmed up (thermostat open) and stop immediately when you turn off the engine.

 

I had a mystery leak coming from the heater inlet hose. I had managed to cut the hose during dissassembly or assembly. The hose would leak under pressure only. It was leaking onto the clutch bell housing and rarely leak down to the ground.
Get some UV coolant dye, and check it with a black light. You put the dye in the coolant, run the engine to circulate it and then check for leaks with a UV light. The coolant will glow green.

 

I HATE that hose on the V6! What a pain! I'm pretty confident I have the hoses routed correctly, but ill check them. I have the coolant system pressurized, and it's held 20 PSI for over an hour now with no leaks. Strangest thing I've ever seen. It has to be be something simple I'm overlooking.

 

I think the fact that after a pressure test with no leaks means that it's not going to be very simple...

If there was an external leak, it would have shown itself by now. Or you would find old coolant crusted on the underside of the rig. That means most likely, your leak is internal. It may or may not be a misdirected hose (not doubting your mechanical skills here), but that coolant is going somewhere. It must be a case where it only leaks when it's hot.

If at all possible, can you do the test when the engine is hot (please don't burn yourself trying though!)? Also, the coolant system must be full of fluid, if it's got pockets of air you're just compressing air and the water is not gonna leak anyway.