My 2000 5.3L Silverado 225K original owner miles, Mostly long trips, Has a broken Valve spring. I discovered the broken spring when changing valve seals as part of my work to fix a P0300 problem with severe misfire problem that started suddenly. Truck was barely running. When removing the broken spring it actually broke in a second place. What is recommended. Should I only replace the broken spring or springs I find or should I be more proactive and replace all the valve springs when installing Valve Seals. Opinions please. I've already finished with installing new valve stem seals on Bank 1 but I'm OK to replace the other 7 springs if that is what is recommended. I'm doing valve seal change without removing the heads because the engine has 195 to 200 lb compression in all Cyl and hardly any leak down and doesn't use oil. I still need to remove valve cover to do Bank 2. If I don't find any more broken springs, could the one broke spring be the cause of a P0300 instead of a P0303? I'm thinking there is probably only 1 broken spring because the truck actually broke one night while sitting in my driveway. It was running fine when I parked it but it ran terrible the next morning. If fixing the broken Cyl #3 exhaust value spring doesn't fix the misfire problem , then I'll be back with other questions.

Myself I would go through the entire heads. If a springs fails tension tests it gets replaced.

I'm not a shop. I'm just an individual who likes to fix problems myself and learn in the process whenever I do have a problem. So, I don't currently own a spring tension tester. How much does an inexpensive one cost? I'm guessing a spring tension tester might cost more than a new set of springs and this might be the last vehicle I would use it on. Because changing another broken spring would not be hard job if another one broke, I was going to reuse the old springs. But after the broken spring broke in a second place when removing it, I started to worry more about other springs. After considering that another spring failure might destroy the whole engine if it let a valve drop into the cylinder and that could leave me stranded a thousand miles from home with a truck load of birddogs, I just talked myself into replacing all the valve springs. So, I have a new question: If you are using new springs do you tension test the new springs? Is there a couple of good brands you would recommend I buy or brands you recommend I avoid?

I would trust any of the long standing performance companies to provide good springs. That being said I would think a cheap set would last the life of the engine.

What carfixer007 said ^^^^^^^

. . . and: Valve spring failures on this engine are unheard of in my experience. Maybe you got a bad one or something. Personally I'd just replace the one unless I had some sign of an issue on others.

Thanks for both of your recommendations / opinion on the valve springs. I decided to wait and do the Bank 2 valve seals and new springs at the same time. So the broken Exhaust valve spring replacement on Cyl #3 fixed my truck. It is running great again. Only Cyl #3 showed any hint of a valve seal leakage and even the fouling on the plug was most likely caused by incomplete combustion instead of broke spring but if the spring wasn't sealing good then I'm assuming exhaust gas was probably blowing past the seal and onto the spring? Could that have caused that spring to be extra crispy and cause a second break? FYI, because of how the spring was broken, it was not even noticeable to met it was broke until I removed it. That spring that broke must really have been inferior material because it actually broke in a second place when I compressed it a second time to remove it again after getting a replacement spring. What do you think is the "Life of the Engine" for a 5.3 Liter that is well cared for with oil changes and using Mobile 1 fully synthetic? Probably 50% of my mileage is from 500 mile to 1K mile trips and another 25% from +100 mile trips (highway mileage). Is there a recommended list of things that you would you recommend I do as preventative maintenance or proactive maintenance instead of waiting for something else to to break? For example, should I start doing any of the following: 1) adding a pint of Mystery Oil to the Mobile 1 oil at every oil change. 2) Start using Lucas or Seafoam in the Gasoline every ?? K miles to help reduce carbon build up on valves. 3) Spray in some Sea foam in the Throttle body and let "Soak" like the instructions recommend? Are those safe to avoid damaging the O2 sensors?
Three maintenance items already on my list are: 1) Greasing the Drive shaft spline to stop the "Klunk" noise when starting to move . 2) Changing Automatic Transmission fluid & filter by dropping the Pan again and also changing Differential and forward crankcase fluids. 3) replacing tailgate hinge parts. One item already done about 3 years ago was, my electronic module that shifts into and out of 4WD was not reliable at going into or out of 4WD. A shop (non Dealer) told me my model truck had an EC fix to the module because the OE models had a problem that it had a risk to say the shift was complete but actually not shift all the way into or out of 4WD even though the lights would indicate that it was shifted. If that happened the The gears would remain partially engaged and cause the gears to Seize and lock up the truck destroying the 4WD transfer case. That fix to the control board for 4WD cost me about $1300 to replace but, I needed it fixed quickly for a hunting trip, I was thinking the fix should probably have been done as a recall instead of as a fix that I needed to pay for. Are you familiar with the problem described? Was I correct to pay for the fix instead of asking my dealer to pay for it?

correction to what I typed in above reply............ ( I think) the fouling on the plug was most likely caused by incomplete combustion caused by the broke spring instead of a leaking valve seal.

It would be a benefit to everyone'* eyes if you could insert paragraphs here and there.

I quit reading when it gets convoluted.

OK, let me break up my questions. I have 225K miles on the truck which I know sounds like a lot but, it is mostly mostly used for long trips. _100 mile to 500 mile trips = 25% of the mileage and 500+ mile trips = 50% of mileage is what I mean by long trips. So with high mileage making up the majority of the mileage and using Mobile 1 do you have any guess at what you think might be the "expected life of the Engine" . for example if the engine is very high risk to need major repair around 300K miles then I probably want to sell it soon instead of waiting for it to break. If the engine with proper maintenance can probably last for +400K miles then I'll keep it a couple of more years.

To help maximize the life of the engine, do you have some recommended actions you suggest I start doing in a high mileage vehicle as preventative maintenance or proactive maintenance? Here are some things I was thinking of doing and I'd like your opinion on these to know which ones if any do you you recommend I start doing. ) add a pint of Mystery Oil to the Mobile 1 oil at every oil change. 2) Start adding Lucas or Seafoam in the Gasoline every 4 K miles to help reduce carbon build up on valves. 3) Spray in some Sea foam in the Throttle body and let "Soak" like the instructions recommend. Do it before each oil change. 4) Drain out a quart of oil and add a quart of Transmission fluid to the oil about 100 miles before my next oil change to clean the engine or would you recommend I use a motor flush instead or just change the oil. 5) Drop the oil pan and clean it out. Are all these things safe and recommended to do or do any have a risk of causing damage to the O2 sensors?

Other maintenance already planned. Remove Transmission pan to clean and change the filter. Drain and replace differential and transfer case fluid.