I've read threads on p0300 codes but none had the mileage mine had so I figured with mileage in mind I could narrow the culprit(s) with your alls help. I've suspected head gasket troubles for awhile. I would start the rig, white smoke for about 5 mins, wants temps built up smoke went away. Didn't think much of it but knew it was coolant. Well my problem now is that about a week ago I was going to work, going up hill rig became a grasshopper and was jumping everywhere while RPM's dropped erratically. After work, started it up and started missing. It smoothed itself out at idle, worked well through the city but once hitting highway began the shake and chug. Checked plugs, all seemed fine. None were wet. Comp test checked out, but that doesn't mean theres not a head or gasket problem. My fear is catastrophic head failure as the rig will no longer level itself out and is in constant misfire. Its only throwing me a p0300. I did all the basic routine checks, before posting. I'm about to park it tomorrow and start tearing it down, but before I do I want a second opinion to justify it. I love these things and I WILL make it last 500K plus. Thanks for any input
High Mileage T4R P0300
- Thread starter ds450xrdr
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Srabai
New member
It really sounds like a head gasket issue to me. How much coolant do you lose? Also, have you done a block test yet? Oil and coolant look ok? If it's not a headgasket, you might want to look into the plug wires. I wouldn't imagine all your coils would go out intermittently. Start cheap and work your way up.
I was losing about a half gal of coolant every 3 months. Nothing crazy, well I don't think so, ive had American V8's go through a gallon a day!. This is my first yota so half gal every three months might be on the high end, I don't know. No block test done yet, but I ill be doing one today. Oil looks great, never has used any and was changed about 4k ago.
It overheated once, about 5 months ago, it was a random overheat as it had plenty of fluid. I caught it before it got to the red, parked it and opened the hood so temp wouldn't climb. After cooled, it ran fine and never had a problem since. The next day I did replace thermostat just to be safe (my guess it stuck). The smoke on start up was occurring before this.
Its definitely a head/head gasket. Started it today, smoked like crazy, I suspected this day would come for awhile. I turned it off, grabbed the OBD2 and it showed P0300 and 303. Hurried and checked cylinder three and there it was, red coolant practically dripping off plug, looked down into the block, more fluid. Smelled like gas, so I know its getting fuel along with a large amount of coolant. Now that I know 100% whats causing it i have a question. When i take the heads off, inspect for cracks and there is none (hopefully) should i send it to get revalved, sprung and surfaced? This thing has 300k, would putting (basically) a new top end on a 300k iron block have interference issues and cause my block to prematurely degrade? I'm thinking if everything checks out, im going to just put the gaskets on. Normally i would take preventative measures and do a complete top end rebuild but no so sure with this one. Its my first yota, so i could be wrong.
Blitzkrieg
New member
PM me your email addy and I will send you additional info on these codes. There are numerous reasons for these codes and some of them even surprised me.
If you are smelling that unmistakeable sweet smell when its blowing white I agree that is almost assuredly a head gasket, but you might benefit from the diagnostics as to why it is throwing these codes.
If you are smelling that unmistakeable sweet smell when its blowing white I agree that is almost assuredly a head gasket, but you might benefit from the diagnostics as to why it is throwing these codes.
