Engine Coolant Leak

Hey Yall!

I need some help diagnosing a problem with my 06 Tacoma!

A family member of mine recently borrowed my Tacoma and drove it to a nearby airport 30 miles away. Once there, the truck started to steam and the truck started "spraying/gushing" coolant on the ground. I wasn't there so I couldn't pinpoint the exact point of failure. The truck had to be towed back home.

I got the truck back and topped the radiator off with water - it looks like I lost about 3/4 gallons of coolant. I fired the truck up and let it run for 30 minutes with absolutely no sign of a leak. All I have to go off of is a second-hand story and the picture below - you can see where the coolant dried.



Any ideas what it could be? I thought the leak would be very clear once I fired it up. Maybe I had the radiator cap on wrong or it's going bad? I initially thought it was a hose or the radiator or possibly the water pump - just praying it's nothing associated with a bad head gasket $$$.

Got any tips or ideas? Thanks!

 

Possible over-heating from a stuck thermostat which is now "un-stuck"?

 

That is what I'm thinking now. Just called up the old man and he said "I bet it's a stuck thermostat, it would be hard for it to be anything else".

I'm guessing it would be hard to diagnose if it's sticking if it became unstuck? Should probably just swap it out.

 

Might be the beginning stages of head gasket failure. The excess pressure in the cooling system may have been pushing coolant out the cap/reservoir

 

Would you recommend a dye test to look for leaks? Any other method I could use to look detect an impending head gasket blow or leak?

I was thinking of just throwing on a new water pump and thermostat to see if that does the trick but I'd hate to put in work if the head is about to blow or already blown.

 

If you had a cooling system pressure tester you could put the system under pressure and let it sit overnight, in the morning if there's no leaks under the truck pull the spark plugs and see if there's coolant in any of the cylinders. If there is then 100% you have an internal leak (head gasket or cracked/warped head)

 

You're not going to see any external leaks if it's a head gasket breach. You could do a chemical block test to check for exhaust gases in the cooling system but that can be tricky if you don't have experience doing it.

You could pressure test the cooling system and then remove the spark plugs and look down into the cylinders to see if any liquid coolant is present. The rear cylinders (5 and 6) had problems on the early 2nd gen 4.0s

I just looked at a ecoboost Ford Escape this morning that had a cyl #2 misfire for a few seconds on startup. I pressurized the cooling system, pulled the #2 plug and saw liquid coolant in the cyl. Ford had problems with their blocks cracking

 

While it's not impossible, it's unlikely, IMO, that something this significant would be the beginning stages of a head-gasket failing. A check of your oil for moisture, coolant level, and a cylinder leak-down test and test for exhaust gasses in the coolant would give you a 98% certainty on the health of your head-gasket. If it passes those, than your head-gasket is likely intact. Assuming that, than, the options are limited and a stuck thermostat would be at the top of them. After that, a failing water-pump, collapsed upper/lower hose, or a partially clogged core or block.

 

Any time I have cooling leak problem I change the radiator cap . I would do that and clean everything up see what happens .

 

No disrespect intended. Is the family member you loaned it to one to be hard on your vehicle? Many years ago back when my little brother was a bit of a madman kook, a car I loaned him came back with a broken transmission and one of the rear air shocks broken in half.

I like to start with what’s easy first. If you don’t have a pressure tester, block tester, leak down tester, all can be rented from a parts store I believe. A new radiator cap is easy.

A dye tester, mines been used twice in the 20 years I’ve had it. If there’s no external leak, no need to use it. It’s only helped on a super dirty oily engine that I couldn’t find the “main” leak. Another time was when I couldn’t tell if it was the engine or transmission leaking, got lucky guessing and confirming it to be the transmission.

 

Looking at your picture, it looks like the leak was from the reservoir cap. Or possibly a pinhole in a hose close to the reservoir.

 

No disrespect taken, the thought lightly crossed my mind! It is kind of a long story, but I was bit by a rattlesnake while trail running, and some family friends had to pick up my truck from the trailhead I parked at. I doubt they would drive wild but there is no way I can know now, I just had to accept their help. A few of my family members flew out to give me a hand and my mom drove it a little around town and it ended up breaking on her (she's a super safe driver)....Nothing like getting bit by a venomous snake and finding out your truck is broken lol.

I got the air leak tester from Oreily's tonight and am going to give it a go tomorrow to see what I find - It was a free rental so why not just check! I agree with @tirediron that it is likely the thermostat and I'll replace the cap while I'm at it because it's cheap!

 

Dang, I hope to never get bit by a rattler. I’m glad you survived the ordeal and lived to tell the tale.

Pressure testing, if you’ve never done it. Radiator should be cool and full. If you need to add a little to top it off, don’t spill because then you won’t know for certain if that wetness is a leak or from your spill. If you do spill, clean it off with some brake cleaner. Be ready with flashlight and mirror to locate a leak source before it dribbles all over. Pump it up, I never go above 15 psi. A quick look from the top, then from the bottom. Gravity will help you find a general area to look from the top again. It should hold pressure but I’ve seen many that don’t.

 

The leak in the picture doesn’t really seem like it sprayed out 3/4 of a gallon. I’ll be interested to hear what you find.

 

send out an oil sample to have tested.

i just went through this, if its not a bad radiator cap then its the head gasket.

My head gasket leak was small, would only show up under higher load such as hauling or mountain driving. Did not leak enough to show up visually in the oil or with a block tester.

Im guessing they needed to borrow the truck to tow or carry something.

Edit: A stuck closed thermostat should be leaking somewhere else since it won't let coolant into the radiator but a bad radiator cap will not hold pressure and let the coolant boil out into the overflow.

 

That is too bad that your head gasket went bad!

My mom was actually the one that borrowed it and she did no such towing lol. I think it could also be a sticking thermostat. I believe the thermostat got stuck, the truck overheated and then it started to lose fluid. It wasn't a small leak but more of a puddle. I've heard when the thermostat gets stuck, fluid can leak rapidly from the water pump gasket....The cap could also be the point of failure if it older (which it is)

 

Maybe closer to half a gallon Most of it ended up on the ground apparently

 

@Waasheem @b_r_o

I pressurized the radiator up to 16 PSI last night. There were absolutely no pinhole leaks or fluid loss. I left the gauge on overnight (12 hours) and it fell and held at 14.5 PSI. Do I need to remove and check each spark plug while pressurized to be sure there is no fluid? Or is it holding pretty close a good sign that everything is likely good?

 

Being an '06, how did the rad cap look?

Being an '06, they are well known for headgasket failures as well. Hopefully yours is not this.

 

Posted before reading this. This is very reassuring.