P148F & slight rattle/shake on startup

Yes more than likely the head gasket is blown out You need to look at the spark plug holes with a camera and see what's dripping but it really doesn't matter something is generally and the water pump was over speeding for some reason More than likely the impeller starting to go bad and it's chunking out as the plastic is rubbing the case sometimes it may overspeed for a few seconds and then start to slow down and just generally not be correct so if you replacing the head gasket and doing the engine work and checking the extension or deck height of your piston sticking up out of the block You want to remember to do something with the water pump Just be careful with this model you can get underwater very quickly I hope your car is in really nice looking shape before you start doing all this work.

 

What’s the miles?

code is for water pump. There have been reports here, water pumps failing around 150k miles. Safest to replace say every 100k. Genuine Aisin WPT-190 or Toyota badged (same) are the replacement options.

More’n likely you just bought someone’s head gasket headache.

Keep an eye on coolant level in the reservoir. Boroscope inspection of the combustion chambers is good for DIY’rs: after car’s been driven and sat overnight. Look for exceptionally clean piston tops, coolant pooling, coolant tears starting at head gasket seam. Pressurizing the coolant system during the inspection may help, accelerate the tearing.

I’d also suspect a stop-leak product, worth checking.

If you do stick with it, do clean the EGR system, including intake manifold, afterwards. And repeat every 50k.


Several relevant links in my signature. Last link is full engine section from repair manual. (On a phone turn it landscape to see signatures.)