Probably what it is, and not too hard to fix.
My long term cuplrit (twice) was the radiator. Can also be a leak in the rear cooling loop somewhere. Can be cut and replaced with radiator hose, among other things. I would go through with a bright flash light end to end and look for green, crusty stuff. FWIW my OEM radiator was partially clogged (who knows what the previous owner did with it...fleet vehicle status). That can be a part of it. I was losing ridiculous amounts of coolant from the failing metal-to-plastic interface. I want to say it was like a gallon or so a month sometimes. Ridiculous! No such problems now, but the truck will burp a small amount over time that has to be monitored (just the way these systems work with a relief valve in the reservoir cap).-P1217 Engine overtemp: coolant 1.5 gallons low; drain, flush, replaced. monitoring levels
-- Why did I loose 1.5 gallons of coolant in 1 yr? Previous forum thread, and will start digging into diagnosis
Did you replace your spark plugs at 100,000 miles? Can be time again. If you have not replaced your plugs, then it's definitely a likely part of the problem if not the problem. When I got that code, I got lucky. I was at around 80-90% of the 100,000 miles and one was a little eroded. Code never came back. There is a standard pattern for troubleshooting this code on all vehicles and it starts with at least inspecting the plugs, where you can catch the problem before your cats go. So...maybe not so bad.-P0420 Cat. Syst. Efficiency Below Threshold, Bank 1: persistent problem. I replaced the cats around 110K miles. I just
reset/clear the codes and press on. Probably not the best course of action, but...I have not done any in-depth
troubleshooting and don't want to replace cats again. Hoping it is a sensor replacement.
Almost certainly the valve covers. My engine is super messy because of this...I have the new covers sitting three feet from me right now but I've been putting it off, mostly because it's not hurting anything (just dirty). If you have a leak down low around your oil filter and down to your pan, or all over your front differential, there is an O ring in the cooler behind the filter that is super easy to replace. If you had the timing chain replacement work done, then you might have gotten some bad RTV jobs or somesuch somewhere. But otherwise, not many sources of leaks except those stupid covers.-Mystery oil leak(s): sides and bottom of engine have oil residue.
-- Frequent monitoring of levels, add oil if necessary, change oil and filter at about 3-4000 miles. Not running synthetic.
-- Awaiting valve cover gasket replacement (mechanic diagnosed). Going to attempt myself
-- I think there are other leaks. Yep, I should get on top of that too, but...
I would start with plugs again? And work my way through.-Exhaust has noticeable fuel smell in cooler temps, but no white smoke
This almost certainly means coolant leak somewhere. If it's in the front too, it's really low or sucking somewhere. Again, my radiator was the cause of this behavior, where I had to constantly "burp" the rear loop by running the gas at neutral with full heat selected, while pointing uphill on an incline.- Interior heat/cooling takes often takes some setting "tinkering" to get the right temp to flow from the vents,
especially getting the heat going on cold days
That one's just kind of a question of what you can live with And maybe how much you want to work on fixing it. My truck mostly lives in doors, and has one little corner where I slapped paint on it because it would be expensive to fix what it was, and I only care so much for a 15 year old vehicle. If my truck were worse, this is something that would make me look for something else.-New AT tires installed at 151K miles. Probably the most valuable thing on the truck right now, after the Thule roof rack
-Body has some dents, dings, scratches and paint peeling all over thanks to Florida sun and I actually take the truck off
road in some gnarly areas during hunting season
Hard to say if you are not seeing other signs. If you are in Florida and not going up and down hills, the cooling system will work adequately at low level, while moving along (I unfortunately know this). If your truck has not been repetitively overheated (code keeps coming back, dummy gauge indicates it), I don't think we've heard of many or any head gasket replacements.Given the symptoms, are they related? Maybe head gasket replacement?