Help! Have 97 4runner with 3.4L auto. coolant seems to be disappearing without a trace. using about a qt. every 1000 miles or so.

have checked for traces of leaks everywhere. there is no puddles on the ground or in the engine compartment. checked rear heater and heater holes....

radiator keeps pressure and is only 2 years old with 60K miles.

no trace of coolant in crankcase or transmission - no "strawberry shake"

no smoke coming from the exhaust.

spark plugs have normal light brown build up with 30,000 use... non is carbon free.

if it where a head gasket problem I think I would see smoke on start up... right?

sooooo. does anyone have any ideas as to where to check next?

 

i had a 86 turbo yota that had similar problem.it turned out to have a crack in the exhaust port. i didn't find it untill it had ruined the turbo. i think it would only leak when the engine was hot.there were no signs of a leak , i guess it was leaking when i was driving because i never noticed a sweet smell from the exhaust. you might try pressure testing the cooling system it might show something.

 

thanks for the note. Have thought of pulling the heads but was hoping these heads are strong enough that they would not crack.

have a radiator pressure tester on the way... will find out soon.

 

I had a BMW that cracked the hose from radiator to overflow reservoir in a hidden place where the fan flow blew the coolant away. It only leaked when the car was in use and left no trace. And that particular hose is immune from pressure testing as it only operates when motor is hot and running and does not pressurize. It remained a mystery for weeks.

Did you try carefully checking the hoses, with the car still running, when you get back from a drive? Especially back and forth from the reservoir? That's how I eventually found it.

 

My daughters 99 was loosing coolant and like yours I could not find the leak. When the engine was hot I could even smell it. When i did the timing belt I found the water pump had a small leak.

 

that could be a sure sign your water pump is gonna die soon how many miles does your truck and do you know if its been replaced ?

 

Get a small extendable mirror and look all around the water pump and thermostat for coolant trails or residue. I think the WP is very likely as mmml4 and Elton said. If you still can't find it, you could do a compression test and/or a leak-down test to rule out a HG or cracked head.

 

"Did you try carefully checking the hoses, with the car still running, when you get back from a drive? Especially back and forth from the reservoir? That's how I eventually found it."

yes, have carefully checked the hoses... with the car running, cannot smell anti freeze.

"that could be a sure sign your water pump is gonna die soon how many miles does your truck and do you know if its been replaced ?"

180,000 miles on the clock. Water pump never replaced. will check it again. hoping it will be it and not a possible cracked exhaust port.

QUESTION to all. If coolant was leaking via the exhaust port, will I see smoke out of the muffler?

 

Why was it not replaced when the T belt was done? Or, was that not done either?

 

timing belt was done 90K miles ago by a dealer... to my surprise they said it was in great condition and would not recommend replacing it.

 

180k sounds like the water pump too me

 

These are all the symptoms of a blown head gasket, I have seen it many times, but you should get the cooling system pressure tested and check around for leaks to be sure. Coolant leaking into the cylinders will not necessarily make smoke, it depends on how much is leaking. If the engine ever overheated it may have warped a head. This happened to my brother's civic earlier this year, but fortunately that is the world's easiest engine to work on.

 

The only symptom he has is missing coolant. All of the symptoms of a HG would be smoke/water out the exhaust, exhaust and excessive bubbles in the radiator, loss of power, coolant in oil or vise-versa.. none of which he's experiencing. I suggested a compression and leak-down test to rule out the possibility of a HG, but I don't think it's the most likely cause - especially knowing that the water pump is still OG and has 180K on it. Do the timing belt while you're in there.

 

Yeah... I hope its not a head gasket as this truck never overheated from day one. The engine is strong without codes or hesitation at any rpm.

Brian, I see you have 200K on your truck... when was your water pump changed?

 

I changed the WP/TB right when I bought the truck at 91K and again last year at ~190K.

 

mine had the t-belt changed at 59k last know service then around 187k the water pump seized up

 

I have the same problem now. Any news on what you found?

 

My old water pump slowly leaked around the gasket and I finally found coolant trails right under it with an extendable mirror and a flashlight. It never leaked enough to drip on the ground, but I would have to add about a 1/2 qt. of coolant every 2 weeks or so. Hope this is your problem too.

 

Thanks

I have just recently replaced the water pump, thermostat, timing belt, all tensioners and drive belts (175k miles). Head gaskets were replaced at 19k miles and I am going thru about 1/2 gal of anti/water mix a day. No signs of any leaking, even the old water pump was sealed tight. No signs of water mixed with oil and no white smoke coming out of the pipe. Compression test was fine (1 cylinder off by 18%) but I have to expect that from 14 year old vehicle. But I can't figure this one out.

 

Believe or not, I am still tracing it. I have pressurized the system at 20lbs and at this point I have noticed a leak by the top radiator hose... Upon examinating it closer, it was coming out of the upper radiator hose fiberic weaving on both ends. Thinking this was the cause I replaced the 13 year old hose. However, I am still losing anti freeze! Looking closer again, I noticed slight weepage from the top coolant tank by the upper hose connection, I had to use a magnifying glass to see the very slow weepage and of course it only happens when the engine is hot.... After a week of driving it's now dripping down that side of the radiator but not hitting the ground... So, I either caused the weak spot in the upper tank to leak more or I have created a leak by pressuring the radiator to 20 lbs. We will see as a new radiator ( oem ) is due in this Friday along with tracer dye just in case the new rad. Does not solve my problem. Btw, the present rad. Is only 2 hrs old that is why I never looked closely at it when I first notice the truck was losing anti freeze... Will see....

I also have driven the car with the timing cover off for 2weeks to see if the water pump was seeping or leaking. It's dry without any dried up water marks in the area.