Engine overheats, coolant level drops

Possible thermostat issue??

 

Now possible it was cap issue. If cap does not hold, coolant will boil at lower temp.

 

I replaced the thermostat

 

AFTERMATH

I replaced the water pump, thermostat and radiator cap. When I reached for the water pump, I realized that it was not in fact malfunctioning (as the impeller was spinning fine) but I'm glad I did replace it because the metal and other two black (some sort of paper) gaskets were in a pretty bad shape. I know I could have just replaced the gasket but the water pump was 120K+ mi old and who knows how much life it had left. Overall, it was a great project and I'm glad I took so many parts out and put them back together, gaining invaluable knowledge in the process. I took the water inlet, all the hoses that go into it (I think a total of 7), put it back on after mounting the new water pump, then put the new thermostat back in. If I had to guess, I'd say what was broken was most likely the thermostat as well as kindof worn out rad cap gasket.

I tried pressure testing the system for leaks with my MityVac generic pump but the adapter was not sealing the rad intake (hissing sound of air escaping as I was trying to pump) so I fitted the tester hose over the resi tank hose fitting that is just near the top of the intake with the actual rad cap on. That actually yielded results and I was able to pump the system to about 10 psi. To make sure that I actually pumped the whole system and not just the area around the cap gasket, I squeezed either big radiator hose that go into the water inlet and that bumped the pressure to 11 psi. So I confirmed there was no leaks.

I replaced my oil and filter but, before putting proper coolant in, I wanted to actually drive it a little with just tap water to see if it will overheat again. The first thing I noticed, when I turned the truck on, was that the check engine light went back on. Since I was at home, I had my OBDII tester handy and got that the code was P0010: Camshaft Position 'A' Actuator Circuit Bank 1. I also looked in the code history and it showed that recently only that one code was showing so I guess that's the one from the beginning of the trouble two weeks ago, referenced in the OP.

I decided to drive it anyway. So took the GF on a small errand road trip, we drove about 50 mi. The engine didn't overheat, however, at one point, just after I parked in one of the pit stops, I popped the hood and noticed that the spillover resi coolant tank was indeed boiling but very small bubbles and assumed that was the case because I had just tap water in the system for testing and not proper coolant. Other than that, everything went fine, the truck drove fine, no funny noise or anything.

The remaining mystery is, how did the malfunction that cause that OBDII code cause the truck to overheat because the overheating happened some 30 min after the code showed? Or could they be unrelated.

 

Good job. Now you at least know you have a functioning coolant system if you stray far from home.

The reservoir tank was likely not boiling, those bubbles were probably just air that was still trapped in the system escaping into the reservoir tank.

I think that code is caused when the Oil Control Valve gets jammed open with gunk or just plain old fails which causes the variable valve timing to not function. I'm not sure how that could be related to the overheating. I also won't be much help on where the OCV is on the vehicle or the diagnostic to check it. I'm sure someone else here knows that though

 

Indeed sir, there's no better learning than when you go trough struggle and don't give up and don't give in... stubbornness not lacking on this side

 

There was a lot of gunk around the bottom of the engine block, especially on the driver's side because I think the left (or both) of my valve cover gaskets are leaking a little. I actually cleaned it with a small wire brush there was a lot it black gunk buildup. Then I soaked everything in Simple Green with a kitchen sponge and rinsed it with a garden hose multiple times. I will be getting replacement valve cover gaskets.

I tried looking on RockAuto for OCV but couldn't find any. Google did return this.

 

What year is your truck?

I've had to replace the head gasket on quite a few (including my 2005 Taco) 2003-2005 4.0's due to a design flaw. Toyota superseded the head gasket in 2006+ 4.0 models.

Common symptoms would be:

* Small, continuous bubbles in reservoir
* Over heating
* Coolant loss
* Rough starts

Of course, you could have fixed it by what you replaced, but keep an eye on the bubbles and coolant level for the next few weeks.

 

2007 (as you can see in my summary)

Which reservoir ?

 

I overlooked that! Whoops!

The coolant reservoir.

 

Do you think I should wait until I put the real 50/50 and burp the coolant system ?

 

If you have water in the system, I'd for sure switch it to a Toyota compatible coolant. Not just for the cooling properties, but to prevent electrolysis corrosion since these engines are aluminum.

 

That is the valve I'm talking about. However I have never replaced one so I don't know what the failure rate is like or how to diagnose whether the part is the real issue.

 

I don't buy brand-"compatible" products. I'm pretty sure Prestone will be fine...

 

Many people run whatever coolant they prefer in their trucks. I've never heard of an issue on a Toyota truck due to the wrong coolant being used.

 

FYI, you did the right thing with the water pump. Even if only the gasket was leaking, you still had to do just as much work so it would not have made sense just to replace the gasket with 120K miles. Water pumps are something almost everyone replaces whenever they have to go into that area of the engine for any reason.

 

thanks. i used black silicone sealant to secure the seal between the gasket and the engine block on one side and the water pump housing on the other side

 

I would be concerned about the continual bubbling in the overflow tank. Indicates a blown or leaking head gasket. As mentioned above it is also in line with the other issues you were having. Keep an eye on it.

 

do you think the P0010 code could be related to leaking head gaskets as well ?

however, keep in mind that the bubbles may be there because i didn't burp the coolant system. i just filled it with water. the bubbles boiling may in fact be air bubbles escaping

 

No, Not related. That code points to the timing via the Oil Control Valve or OCV Filter.

Are the bubbles steady? Do they increase with engine RPM? I have never seen steady bubbles due to air in the system. If it increases with RPM chances are you have a head gasket issue. Pop the lid on the overflow tank and smell it. What does it smell like? Exhaust or Gasoline?