Random Overheating Issues. Please Help!

Fixing the coolant leak doesn't deal with the overheating unless low coolant caused the overheating. In which case, most of this thread is irrelevant.
Go ahead. Jump in and pull the head first if that's what you think is best after all, the thermostat, sensor, pulling the spark plug didn't fix it.
Might as well get the big stuff out of the way. No point in testing anything.

 

Definitely worth going through all the basics. Even pulling the thermostat out again and making sure it’s not in backwards or a failed OEM part. It happens

 

I kinda skimmed through this... but seems like the water pump stopped pumping. My 1st water pump blew at 25k, so I wouldn't go as far to say its impossible. No coolant loss is the main concern here. Can also be the radiator cap may have come apart and lodged somewhere clogging up the system.

 

Your missing the point. Find the leak, go from there. I'm not just gonna pull the head unless it's confirmed that's the problem lol. Who said pulling the spark plug was gonna fix anything?? If there was coolant setting in the cylinder then that would confirm the problem.

At this point I'm pretty sure my whole problem has been coolant lose and getting air in the system. My first post was before I diagnosed that I was for sure losing coolant.

 

Thermostat can only go on one way in this trucks unless I am missing something. It is a whole assembly in a plastic tube that has a flange that mounts with 3 bolts. There isn't another way to put it on. Also if this is the cause, wouldn't it be odd that it works for hundreds of miles just fine?

Radiator cap was replaced and even the stock one didn't have anything missing. Also though about the water pump but it's kinda like the thermostat probably, why does it work for hundreds of miles and then stop, then work again.

Hope this pressure test gives me some answers. Thanks for the recommendations everyone.

 

Welp pressurized the coolant system and yep the head gasket is toast.

Can anyone point me how to a tutorial on how to change the head gasket? And maybe a kit to purchase? I've done just about everything else to an engine beside take the head off. Would a hayes manual be a good option? I've used one on my jetta to change the timing belt.

 

Probably the Toyota TIS site. Pay a 3 day fee and download all the manuals your heart desires.

 

Sorry to hear this bad news, that morning miss is dead giveaway of head gasket issue.
Unfortunately this repair is way more involving than timing belt on Jetta. My suggestion is to take BOTH heads off and send them to the machine shop to get checked for warpage and cracks. MAKE sure to check your block THOROUGHLY for warpage, if your block is out of spec your repair job is done, look for other engine. If block is good and heads may be machined to be flat AND STILL IN SPEC than start sourcing your miscellaneous parts for assembly. Good service manual is a must for repair like this!!! If repair possible, it will be a lengthy one (if you are doing it, TAKE YOUR TIME!!!). If your truck is your daily find alternative way of transport BUT DON'T be in a hurry to do this job.
Good luck.

 

The Haynes manual would likely not be sufficiently detailed/complete for that job although having one on hand for general reference is a good idea. The Toyota TIS subscription could work. Another option would be an Alldata DIY subscription for a single car - you can do that for $20/mo or $60/yr. It is the same OEM info that is in Toyota TIS. I like having the Alldata access while I'm doing a big job like that in case you come across something you didn't anticipate and would not have printed out. Plus, there are hot links in the procedures that provide detail on individual steps which makes the printing out a bit of a pain.

https://www.alldata.com/diy-us/en/diy-repair-information

 

I have the Haynes and can confirm that it is not suitable for this.

 

Find attached base procedure from FSM for removing & installing head gasket on 5.7L. "Info" buttons are hot links to more info on that step and lots of work to do before you get to the head gasket procedure. All that is detailed in other sections of the FSM. This is what you will get in TIS and Alldata and will need to navigate to the other sections as required.

 

There are some jobs I wouldn't tackle myself....this is one of them.

 

Sorry to hear that. I would watch this video for concerns that are directly related to your situation. It covers head gaskets and the metallurgy of the 3ur heads and block. May not be the news you want but it’s definitive at least https://youtu.be/dfGTI0sWozc?si=MXJCw82BTFQ0QSKD

 

Thanks for posting the video. Engine coolant acidity resulting in head gasket damage is definitely a thing. Heard about this issue on the 5.7L and checked the conductivity of my engine coolant which is an indicator of acidity. It was 0.003V DC vs my rule of thumb max of 0.3V DC so felt ok but went ahead and replaced my coolant at 87,000 miles in Nov '24. Used Toyota pink and replaced the thermostat and radiator cap as well. Currently at 98,000 miles and will do it now every 50,000 miles.