I'll try that in the morning and see how the pressure holds. Part of the reason I wanted to replace the plenum is the brake booster vacuum line is all gummed up with gasket maker. Assuming PO had some issues and went that route instead of fixing it..

 

Pressure is looking good! I did the TBH delete (ran a hose directly from the reservoir to the intake manifold -- didn't do a U or cap the ends) and tightened up a few hoses. Held 15 PSI with no drops for half an hour. Ran it at idle up to temp and still no leaks. Doing another flush to get rid of the last of the green coolant so I can switch over and I'll keep monitoring it.

I probably won't have time to dive deeper into the engine and check the heads till late next week, but driving around with no thermostat, temperatures stayed under 175. No bubbling in the coolant when I stopped.

 

What are you getting rid of the green coolant for and what are you switching to? Most folks here run green and run away from pink dexcool which coagulates when exposed to air... Also you should pump that pressure up to 18-20 just to be sure. Otherwise congrats so far!!

 

@uhoh_elmo yea stay away for dex - green is a far better choice. I am with @Dave03S put a 170 thermostat if you are not throwing codes without one a 170 will do, MPG might suffer but otherwise I believe you will be fine. Go for a drive around the block you need 20 -30 minutes adn up to 2000-2500 rpm a few times If you get no white smoke,no temp spikes, and no coolant loss after that, leave it alone do bother disturbing anything else.

You may have gotten lucky and dodged a bullet, but start saving up if you have to do the heads in the future.

• Monitor the temps like a hawk
• Check the coolant level every morning
• Check under the filler cap every morning for yellow.
• think happy happy thoughts

 

I was going to switch to Valvoline Zerex G05. I know people mention to stay away from dex cool as it eats away parts of the system. From the RAVE, "Use Havoline Extended Life Coolant (XLC), or any ethylene glycol based anti-freeze (containing no methanol) with only Organic Acid Technology (OAT) corrosion inhibitors, to protect the cooling system." The only coolant I saw at autozone with the OAT was the Zerex G05 - and it is not dex. I think I've seen it mentioned on the forums as well.

 

I have gauges coming I'm going to mount directly in my line of sight to be sure. Been driving around a bit more today as well and all seems good. No leaks or smoke. Fingers crossed!

 

Normal green coolant is fine for the cooling system, it will basically last forever.

BTW, in my experience cooler thermostats get BETTER gas mileage. Both my 00's run 170's and get 17mpg consistently at 70 mph.

 

IMO you’ve already blown the head gaskets at minimum.

id start tearing it down and have a machine shop work the heads

 

I noticed that a few years ago when I got the inline thermostat. Engine response and mpg went up. Not 17 but 15-16 mpg hwy

I wonder what LR was talking about for the reason to run so hot was to improve emissions?
Maybe some other gases that get produced not mpg I tell you

 

Well, as Richard said, I'm hesitant to tear down the engine if everything seems to be working. Drove around for an hour this morning. Half city driving, half on the freeway holding a steady 65 to 70 mph. Temps never got above 180 and generally stayed around 170 (57° F ambient). No smoking nor leaks. Also went through the drive cycles to clear my check engine light for the new front O2 sensors I installed yesterday

I don't know if I was partially saved because I had fresh fluids in when I overheated. But given I have no leaks, driving around for an hour caused no issues or temperature spikes, I'm going to leave everything alone and be hyper vigilant about monitoring my temps. I am still planning to complete my last flush and install the 180 deg thermostat that came with Extincts inline kit. If that should cause anything to change, or if I notice any other issues, I will definitely follow up.