P0306, overheating but, no sign of HG failure? What is it???

[Azca]

Back from a short trip to Northern AZ. On the way up to Flag, the last grade between Sedona off ramp and Flagstaff, I had her in second gear around 4500RPM and she starts to slow and run rough, almost immediately CEL comes on. (and I left my scanner in the Camry).

Pull over and shut her down immediately, walk to the front and coolant is pouring out of the coolant reservoir. .

Now I NORMALLY keep water in my vehicle on any trip, especially when I am going out into the backcountry. This time I decided to wait until I got to Flagstaff to pick up all my supplies. .

So now I have the kids running around gathering snow from the side of the hill that I parked next to and am throwing as much as I can onto the engine and radiator as fast as we can. Luckily I made it far enough north and parked next to a spot that had protection from the sun.

Now after it cools we stick a half bottle of water in it and find the cleanest snow we can to pack the bottle the rest of the way. After about 45 minutes we limp to the nearest convenience store and get bars leak (just in case) and water. Got to an Autozone and they confirm P0306. She is running just fine now...

Now for the question. After putting on another 6 hours of driving with about 200 miles I see no sign of a HG failure and after a day and a half even climbed a pretty nasty 500' change in elevation which required use of the rear locker and in places, the front as well. No foam on the oil cap, nothing odd looking in the coolant reservoir. No water leaks, new radiator, water pump, hoses, fan clutch and coolant change in the last two years. EGR, new wire and just about every vacuum line has been replaced (that I can reach without pulling the intake) have been replaced in the last two years.

Never a hint of an overheating problem driving in Phoenix, even in traffic (max temp I had seen was mid 210s.) The truck is running fine, I lost a little water only because I completely filled the reservoir, now it is at the full line. Spark plugs are less than 6 months old but, are one step cooler than normal, I have been chasing an engine knock...

So what would throw the P0306 and cause it to overheat given the above?

 

[george_tlc]

p0306 is a misfire on cylinder 6. I had a p0306 and it didn't "go away" and ended up being a dead injector. A misfire will certainly f'up your running temps, especially under load.

I had a very occasional rough start up (maybe every few months) which has NEVER come back after the injector finally failed 100% and I replaced it.

Of course misfire is also commonly due to the harness near the EGR or for some behind the glove box.

Good luck on diagnosis, I'd check the obvious harness issues first.

cheers,
george.

 

[Azca]

She seems to be running rougher now, but not terribly noticeable. I also popped the hood this afternoon and found a broken fan belt, didn't see that before, not sure when it actually went.

If I have to take everything apart to get to the injector and wiring I am thinking of just doing the head gasket anyway. I also see that the power steering pump that I put in a year and a half ago also appears to be leaking and, I still have the upper oil pan leak. I might just pull the engine to get everything done at once...

 

[98 SNAKE EATER]

A few months back, my rig lost power on the highway and the temps shot up a bit (enough to disable the A/C, but not spike the needle)

No codes thrown

Turned out to be a clogged cat

https://forum.ih8mud.com/threads/ha...-the-drive-home-temporary-overheating.813602/

 

[elhombre]

Try pulling the #6 plug to see what it looks like.

 

[Azca]

Snakeater, the cat may be it. It only got hot when I was really working her and then 6 misfired.

Elhombre, yep, set to to that tomorrow (yes Christmas). Also replacing the broken belt.

Unfortunately she is running rougher with a slight stumble every once in awhile.

 

[Azca]

Just got done with today's work. Removed spark plug, pretty good carbon build up so it does not look like I have a HG failure but still will test. Found a leak at my heater valve, the valve itself is leaking as was the hose connection. Tightened up the clamp and fixed one, will need to pick up a new valve.

This was just dripping, once ever 4 to 5 seconds, I don't think it was leaking enough to cause the overheating. Still running rougher than before, I will be dropping the cats this weekend, with the way this is burning oil, clogged cats would not surprise me...

 

[98 SNAKE EATER]

Still running rougher than before, I will be dropping the cats this weekend, with the way this is burning oil, clogged cats would not surprise me...

Just curious, but what brand and weight of oil are you using?

 

[alia176]

One huge hint I have is that you have coolant pouring out of your overflow tank, second hint is number six misfire. These two things are leading me to believe that do you have a head gasket failure of some sort. However I could be wrong but investigate as if you have a head gasket leak. Remove all the spark plugs and compare to see if any of them I getting washed clean. Rent a radiator leak tester and check out the coolant system.

One possible reason why your catalytic converter is overheating is because number six was dumping raw fuel into your exhaust system. The biggest clue so far is that you had a power loss all of a sudden and that just does not happen if your cat is clogging up slowly. You would've had a power loss for a long time.

Another common test for head gasket leak is to top off the overflow bottle with coolant , warm up the engine and then have somebody rev up to 4000 RPM while you look for aquarium style air bubbles coming out from the bottom.

 

[Azca]

Just curious, but what brand and weight of oil are you using?

Mobil 1 - 10/40 high mileage

 

[Azca]

One huge hint I have is that you have coolant pouring out of your overflow tank, second hint is number six misfire. These two things are leading me to believe that do you have a head gasket failure of some sort. However I could be wrong but investigate as if you have a head gasket leak. Remove all the spark plugs and compare to see if any of them I getting washed clean. Rent a radiator leak tester and check out the coolant system.

One possible reason why your catalytic converter is overheating is because number six was dumping raw fuel into your exhaust system. The biggest clue so far is that you had a power loss all of a sudden and that just does not happen if your cat is clogging up slowly. You would've had a power loss for a long time.

Another common test for head gasket leak is to top off the overflow bottle with coolant , warm up the engine and then have somebody rev up to 4000 RPM while you look for aquarium style air bubbles coming out from the bottom.

I pulled #6 and #2 to compare, very similar in look. A lot more carbon build up than I would have thought after about 6 months however. I am going to do the HG test, ordering a test kit today.

In the end I may just be replacing the HG anyway, I am eating about a quart of oil every thousand miles now, also been chasing a knock demon which appears to be due from carbon build up. I have a leaky #1 oil pan at front and rear and a few other niceties I should address. Think I am going to just pull the engine and do everything at once including the timing chain replacement. I am getting too old for gymnastics, so I think it would just be easier to just pull it and work on it all where I have unrestricted movement. Unfortunately I will be a couple of months before I can take time off to get to it.

 

[alia176]

I pulled #6 and #2 to compare, very similar in look. A lot more carbon build up than I would have thought after about 6 months however. I am going to do the HG test, ordering a test kit today.

In the end I may just be replacing the HG anyway, I am eating about a quart of oil every thousand miles now, also been chasing a knock demon which appears to be due from carbon build up. I have a leaky #1 oil pan at front and rear and a few other niceties I should address. Think I am going to just pull the engine and do everything at once including the timing chain replacement. I am getting too old for gymnastics, so I think it would just be easier to just pull it and work on it all where I have unrestricted movement. Unfortunately I will be a couple of months before I can take time off to get to it.

I think you have the right plan, just save up the parts and then pull the engine/drivetrain out and do a thorough job all at once. I propose to folks that pulling the engine out and doing the HG and other things is more prudent than just pulling the head out.

In the mean time, pour in some Barr's stop leak and then drive her like you stole her. I blew my HG with the same exact symptoms, about 700 miles from home. The misfire stopped the moment Barr's stop leak hit the block. It was rather amazing!

 

[Azca]

Well just checked to see if the gasket was leaking and the test shows it is fine, fluid stays blue after a considerable amount of pumping when the engine is being reved. Did not pull the cats, ran out of time, guess that will be the New Years Day chore...

 

[george_tlc]

You seem to be heading in a strange direction given your first post talked of P0306 misfire on #6.

Do you still have misfires? At idle? Read all the codes and report back.

What's the history of the ignition system? i.e. age of spark plug and coil leads? Are they oem or ? Rotor age? Distributor cap age? Timing setting? Injector harness condition near EGR and behind the glove box?

Clogged cat would be quite obvious in terms of power loss and seems unlikely to specifically cause a P0306.

If indeed you don't have a HG issue, then check my signature and you'll find a writeup of my P0306 debugging and repair that may help you stay focused...

cheers,
george.

 

[Azca]

No misfire's, no codes at this time (I have a ELM 327 plugged in and have been monitoring it ever since I got back last weekend). She is running rough with just a bit of a stumble here and there. When I say rough, it was running darn nice before, not smooth as glass mind you, but very nicely. After it overheated, she has not been running as smoothly, even my daughter noticed it. That said I am not sure many would say it was running poorly.

Cap, wires, rotor are all less than two years with about 20k miles on them. Plugs were replaced this summer with a one step colder plug. Timing is on, checked it again this summer. Coil is original, but I don't think it is the culprit. EGR is also new, last year and a half. 90% of all hoses are new as well, all except the ones under the intake and to the hoses for the rear heater box. In fact I have replaced most of the emissions parts over the last two years baselining the rig.

I did not attack the harness, as you know the location sucks, I will cut into this weekend. Certainly have not looked behind the glove box but will.

I am still in the dark as to why it overheated in the first place, will a misfire under load cause this?

Will spend time going through your thread again (one of the first I read on this actually) and see what I may be missing.