Overheated at idle, then again driving

[KD5NRH]

After some stop and go traffic, I was eating in the car with A/C on, noticed it was running near the red. Shut it down while I finished eating, and when I went to start it up again, it was rough and died right away.
Let it cool off all the way while I dug out my emergency gallon of premixed coolant. Once the gauge was near bottom, it cranked right up, and adding the gallon while it idled brought it to where I could see it in the rad. Idle was smooth and sounded fine, so I figured maybe I just lost the fan clutch and can't idle in hot weather now.
Got about a mile and got stuck at a long light, it climbed back to about 3/4 while waiting. Took about another mile to get to a safe place to shut down again, and with the heat on full, it was in and out of the red, going 35-40 with what felt like normal acceleration and no stuttering.
Popped the hood and there was steam coming from the rad cap, overflow and under the intake, pretty much top middle. Nothing on the ground either place except A/C condensate, no CEL, oil doesn't smell or taste of coolant and good level. Pulled a couple of spark plugs while in waiting for the wrecker to show up, and they're clean and dry, nothing in the holes.
Did I blow the head gasket? Still seemed to run fine with no noticed loss of power, but I was way more focused on finding a safe place to sit long enough for AAA to get to it. Not going to risk cranking it again until it's totally cooled off for a few hours in my driveway and refilled.

Just got it in July, so I'm not sure about any previous engine work, other than something has been done to the ECM that it will connect to ELM327 based readers (tried 3 with the same results) but no PIDs available. I can clear a CEL, but not read the code or see any other data. Has been running pretty solid, no leaks, though it needed a bit under a quart of oil after around 2000 miles.

 

[2TH4IST]

Does the system hold pressure? Then check for any leaks. I had my intake manifold gasket rust out and leak. Never overheated but never built up pressure and no drips on the ground. Let it cool completely, with a full cooling system. Then check if there is coolant in the cylinders. How is the radiator cap?

The coolant has to be going somewhere. It doesn't just evaporate.

Also do a head gasket test with a head gasket tester/block tester. With that blue fluid that changes to yellow if exhaust gases are present.

 

[KD5NRH]

Doh, didn't even think about the intake gasket. That would be dead on for where it was steaming from the engine. Still waiting for the wrecker to take me 70mi home, (AAA Premium is worth every penny when you drive old vehicles) but that's going to be the first thing checked when I dig in at home since I'm sure 90 minutes waiting and an hour going down the highway on a rollback will have it pretty well cooled off.

Fingers crossed for a cheap, quick and decisive fix, since I need to get back to the city for a MRI later in the week.

 

[2TH4IST]

Yep I hope that is it for you too. We'll thet intake gaskets can cause some of the studs to rust and break off, which then turns a easy job to a real PITA. If that is the issue make sure to clean the sealing surfaces well.

Also check your radiator cap, make sure it hasn't broken apart. I'd stick with oem for the cap if you can. But you got to do what you can in a pinch.

 

[KD5NRH]

Found it: stuck the hose in the rad and just started gushing water in until it started coming out somewhere. It's the bottom end of one of the TB lines, where I couldn't see last night. Putting a stream right up into the valley, that splashes off the lower intake gasket seam.

So now I just have to figure out how to get the TB off mostly one handed, (right shoulder is on a "nothing heavier than a large soda" restriction) see if I've got some suitable hose here, and then either repair or bypass. (It's Texas: we have very few days when a heated TB is even remotely useful.)

 

[KD5NRH]

Well, I didn't know why I picked up a 10' piece of 5/16 high pressure fuel line on clearance other than it was cheap, but it fit perfect to replace that hose.

Hose came completely apart when I tried to take it off, and required some creative needlenose work to get the bottom bit off the fitting, but the fuel line was a perfect fit, and after filling it up with water, letting it come up to temp and idle a bit, no sign of any leak, and the top rad hose is firm so pressure is staying in the system.

Just have to run to town later and get some coolant and I should be good on this one.

In a way, I'm kinda glad I didn't spot that last night: I had the tools and the hose in the back, but I'd have been seriously scared about the test drive being 70 miles of rural highways, and annoyed about having to go that far to get cleaned up properly afterward.

Maybe I should have replaced the other hose too, but frankly, if it fails, I'll probably just bypass.

 

[JohnMc]

Another set of out of the way obscure coolant lines are down by the oil filter - running coolant to the oil cooler. As these cars age, people will often change the bigger, more obvious ones (radiator, heater), but not the smaller, less obvious ones (like the TB, rear heat, oil cooler). Any of them can strand you, though.

 

[2TH4IST]

Yes you are correct. I replaced all the hoses a few years ago, all with oem toyota. I don't remember the cost, think it was around 175-250. Not bad for all the hoses.