Coolant Reservoir Bubbling and Filling Up.

Hey guys,

Just so you know, I've been reading and reading and searching and searching, not only this forum but many others...

So I know this is typical symptoms of a blown head gasket but I have done many tests which aren't giving me a definitive answer just yet.
The truck drives fine but bubbles and fills up the reservoir with coolant. This is because there is air (or possibly gas) filling up the cooling system. Eventually, after maybe 2 hours on the highway, after getting off, the engine temp will start to rise. At this point the rad cap needs to be opened to bleed off any excess air in the system and then syphon the coolant from the reservoir back into the radiator(this never happened to me, but the previous owner about 5 times only on long road trips). Since owning it, if I constantly(like once a day) syphon the coolant from the reservoir back into the rad, it never overheats and everything is fine.

Fan/Clutch, Waterpump, Thermostat, Rad cap were all replaced by the previous owner about six months ago(a friend of mine, all using OEM parts). Ive since purchased another OEM rad cap which had no change in results.

Block Test:
I first brought it to a mechanic to have the block test(hydrocarbons in coolant) done. This came back negative or inconclusive... but it was bubbling at the time, and those bubbles didn't seem to contain carbon dioxide..

Cleaned the Radiator:
I took the radiator out and completely cleaned the fins out as they were full of dirt and also ran a hose through both ends of the rad and water flowed through the other end without issue.

Compression Test:
I then did a compression test and my results are as follows:
Cyl1 @ 179psi, Cyl2 @ 180psi, Cyl3 @ 160, Cyl4 @ 175psi, Cyl5 @ 153psi, Cyl6 @ 182psi

Cylinders 3 and 5 seem to be a bit low(right beside each other) but at the same time they are both above the accepted 145psi mark, however are below the 15psi "difference between cylinders" mark.

Coolant System Pressure Test:
The coolant system pressure test kit is very expensive so I makeshifted one together. I pumped up the radiator using a cork with a hole drilled in it and a pressure gauge hooked up...a little ghetto, but that showed a leak from about 30psi to 10 psi in 3 minutes or so...

Basically I'm at a bit of a loss... there are no visible leaks anywhere. The only real loss of coolant seems to be from it overflowing on a long highway run and not being consumed by the engine. No puddles in the drive or anything like that... Its somehow just sucking air into the system..
Sorry this was long, im trying to give as much detail as possible for my benefit and also any one else in the future experiencing these same symptoms(if im able to get it sorted out)

Possible causes:
- bad heater core?
- hole somewhere that allows air in but no coolant out?

Any help other than one liners saying: "Head Gasket" are very much appreciated, unless you can give me a real explanation as to why this is in fact symptoms of a compromised head gasket.

Thanks
Josh

 

For pressure testing, auto zone or advance auto parts is your best friend. They will loan you a really good pressure tester at no cost. You have to put down a deposit, but it is returned when you return the tester undamaged. I usually use a credit card to make this painless.

My first thought would be a pressure test and try to watch carefully. Or inject an ounce of leak detector (cooling system approved) and pressure test. A UV light will help find any leak.

If you have a leak, the water has to go somewhere. On the ground (or hidden on the back/top of the motor, etc), in the oil, or else directly into a cylinder which would make the truck hydraulically lock and not turn over if water is in a cylinder. I can only assume you have no water in your oil, which would be bad. And you are not seeing any hydraulic lock or excessive steam in the exhaust, which is also bad if you see these. It is possible that you have a leak on the input side of the water pump so that it sucks in air rather than water. But if so, the pressure test should reveal the location, particularly with the dye. If it doesn't, leave the dye in and drive for 30 minutes. Come back after dark and break out the UV light. Look for a green tell-tale somewhere. I have tracked some really painful leaks this way that I could not find any other way. But that green trail will help. Be aware that where you see the green might not be the source of the leak. That could be hidden behind something and you might only pick up the green glow farther back where the water has spread due to air flowing. But be diligent in your search and the most forward green point on the engine is likely the guilty party.

I have never seen your specific problem, but based on my 68 years of living, I am sure there are a LOT of things I have not seen. Every day is a learning experience for most of us.

BTW I have seen leak tests that were not helpful. What if the radiator itself leaks near the top, or around the upper hose? You might only lose air when pressure testing, never seeing the leak revealed. So you have to play with this a bit to test, then add water, and test again, until you have no air left. At this point, you might need some soap and water to look for a high point air leak, but it isn't going to be far from the radiator top. Not on the block if this is your problem.

 

Sorry, not allow to say what is probably 99% the cause.

The cooling system is under about 15 PSI from the inside. Nothing is getting into the cooling system through an external source. It's from an internal source which we can't say.

Gas escapes the combustion chamber through a crack in the unnamed part between the head and block. Coolant channels are right next to the cylinder and so the gas makes it into the coolant. When the coolant circulates to the radiator the exhaust and un-burned fuel/air is lighter than the coolant and rises to the top in the form as a bubble. Also coolant leaks back into the cylinder and turns into steam coming out of your exhaust. The amount of steam may not be large enough to "see" but it's there.

 

Not sure what you are saying, but the coolant was, according to the OP, analyzed and there was no trace of exhaust gas present. Which means it is unlikely this is the cause. Also a pressure test would dump water directly into the cylinder and make it impossible to turn the engine over afterward. Again, this did not happen. Head gasket is possible, but not very likely based on the testing already done.

 

There is no place that will suck air into the system and have it only bubble out in the coolant tank. You have a blown head gasket is the highest probability. Usually around cylinder # 6....

let us know what you find.

 

Pressurize the cooling system for at least couple hours with a loaner pressure tester if you can get your hands on one. Remove the spark plugs, and have someone crank the engine over. Mist is a dead giveaway, as is any traces of pink - assuming you are running the OE pink coolant. Or wetness on the plugs / in the cylinder(s).

 

Searching this forum, you will find that 2005-2006 models were prone to having a bad head gasket. #6 as reported by jimmyh is common.

With the engine cool, remove radiator cap and start engine. If you see bubbling going on at the top of the radiator neck as it gets warmer, you very likely have a blown head gasket. I'm not talking about the coolant rising or maybe just a bubble or two.


Update:

I ran across the following on the web years ago. Though I had no use for it at the time, I saved it for future reference. This was in a Motorage Magazine or one like that around 2004:

Fill It Up: Being fooled by chemical testing/infrared testing of the cooling system for head gasket failure(s), I stumbled on a better method, which is much faster and more accurate, too. Next time, try this:
1. Remove all the spark plugs from the engine.
2. Fill the cooling system right to the rim of the radiator neck.
3. Disable the ignition system.
4. Insert one spark plug in a cylinder and then crank the engine for five to 10 seconds, while watching the radiator level. (A remote starter comes in real handy here.)
5. Repeat step 4 above for all cylinders.
The idea behind this is simple: This uses the engine’s compression to pressurize the combustion chamber and force this pressure past any potential head gasket/cylinder head leakage into the cooling system. Should there be a leak, the level in the radiator will overflow. The reason all other spark plugs are left out is to allow the starter to spin the engine faster, without shaking so much and helps to identify which cylinder is the culprit. Why not let the 150 to 200 psi compression do the testing? Now, 13 to 15 psi in the radiator to test it just doesn’t seem up to the job anymore, does it?
Brad Petersen, Owner, ASE L1 Master Tech, Peterson Automotive, Escondido, CA

 

Excellent idea and posting Lester! My hat is off to you sir.

 

What does the oil look like. This will usually show a blown head gasket pretty quick.

 

I've seen many with a blown head gasket that have no oil contamination so it's no definitive.

 

It doesn't have to be contaminated but if it looks like a Frosty thats pretty definitive.

 

What I'm saying is you can a head gasket that's failed and will plush combustion pressure into the cooling system but will not contaminate the oil. The most common failure. The other failure is where the gasket will fail and coolant will leak internally into the motor and mix with the oil. It rare to have both. Other ways to get coolant in the oil are a cracked head, oil cooler failure, cracked block and coolant seeping through unsealed bolt threads. So coolant in the oil is not definitive of a head gasket failure.

 

Ruggybuggy has it correct.

Lots of Tacoma's have blown head gaskets around cylinder # 6 without a milkshake in the oil ...

Usually that only happens with a crack in the block or head or the gasket failing between a cooling passage and a oil return passage.

 

Alright guys, thank you all for the input! After checking everything else, I went and rented the Block test kit and also the Coolant System pressure tester to make 100% for myself what is going on. I was losing PSI pretty quickly on the pressure test, so i went ahead and did the block test. Almost immediately the blue liquid turned yellow... COMBUSTION GAS IN THE COOLANT! Freaking mechanic I brought it to didnt do the test correctly. After watching many youtube videos and using an actual kit myself its pretty obvious to me why the test the mechanic performed did not show positive. He didnt have the bulb to actually suck and gas or air from the radiator into the liquid... he was just holding his hand on the top hoping that somehow the gas would push its way into the liquid.... anyways, that was a huge waste of $80 and also a big waste of my time. I will surely be diagnosing my own engine problems from now on.

I really appreciate everyones time to post, I wasnt trying to say it wasnt a head gasket problem, but more looking for answers on how it could be combustion gases or air entering the cooling system after the Block Test (which I paid for) came back negative... anyways, ill be pulling the head off tomorrow and will report back on whether or not its a cracked head, warped head, or just plain old head gasket. The issue seams to be around cylinders #3 and #5 from the compression tests I performed.

Ill keep everyone posted.

 

When you have the head off you might want to invest in having a machine shop check the head for cracking and straightness.

 

How many miles does the truck have?

 

My only experience with a blown head gasket was on a totally different type of vehicle, but the symptoms were pretty spectacular. My 1949 Ford 8-N Tractor, with a Flathead 4 would actually blow coolant out of the radiator top like a small geyser when it was being cranked! I would take the cap off cold to check the coolant level, and top it up, since it did drip a bit, being a 65+ year old engine, but when I would crank it, it would blow almost a 1/2 quart of water out the filler neck!
Once it got a new head gasket put on, never did it again!

 

Chances are very high that it is only a gasket issue as they did have a design problem in your year model.

A little advice from me if you can afford the time and money. Since you are tearing it down that far it would be in your best interest to replace BOTH Head Gaskets now. It would suck to have to do the same thing on the other bank in a few months...

I wish you the best!

 

@tacomakid96 the truck has 210k miles on it.

Alright guys, both head gaskets are replaced! ran the truck around town for the day today and runs like a champ. The heads seems straight to me and the old man, so we didn't have them checked. We could clearly see where the seals had failed, mainly between the two cylinders #4 and #6, cylinders #3 and #5 had questionable leakage points towards the outside edge of the head.

That was way more work than I thought it would be.. took me and the old man 3 days to get it done, and we worked about 12 hours a day. Didn't do a complete valve job, but used the grinding compound with the suction cup baton tool so just get some of the carbon off the contact points. Everything about the motor looked pretty clean and good. Glad its all back together and running well. Taking it on a road trip next weekend, fingers crossed!

Thanks everyone of the input!

 

Glad to see you got it done. Not an easy task.