Of my thread in the Jeep section:


https://dodgeforum.com/forum/jeeps/3...p-carnage.html

 

Sorry to hear that about your jeep.

What caused the valve to drop, and is there anyway to prevent it?

 

I could just say "read his whole post", but that isn't very helpful, and I'm feeling magnanimous today.

Aluminum head for weight, steel valve seat for durability. These two materials have different coefficients of thermal expansion. Apparently, when the engine gets really hot (remember, water temp ain't nearly as high as the temp of the cylinder head!) the head and the seat forget to stay together. Seat drops down onto valve head and rides up and down the stem, banging into the cylinder head and valve head, until it becomes little pieces. The little pieces go everywhere, and since there is now valve seat to stop air from going up the intake manifold, pieces go up there and get sucked into other cylinders. At 1200 RPM (fastish idle) this happens 600 times per minute, ten times per second. Done before you have time to think about shutting it down.

I'm only guessing, because there were no witnesses.

It is amazing that these things even run around the block (all engines, not just ours) given all the stuff that goes on inside them!

 

Yep, that pretty much sums it up. Good explanation, gator.

As I said in the post, MOST have this happen at some point after an over-heat (although it can be up to months later). I didn't really have any over-heats although when my radiator split I ran up to about 220* which I don't consider an overheat. There are a few instances where guys reported losing a valve seat and never ran hot, but in my inquiries I'm finding a good 80% of guys who dropped a valve seat admit to having an overheat at some point.

So I guess the moral to the story is DON'T let these engines get hot! Spend the extra time and a couple bucks on keeping the cooling system well maintained. You may still have a dropped seat at some point, but the odds are more in your favor if you never let it over-heat...

 

good advice..careful with the e-fans guys!

 

Thanks for the heads up . I'm overdue for a cooling system maintenance as it is. Anyone have a ballpark figure of whens a good time to do the water pump?

 

When it starts leaking...thats when I did mine.

 

Thats a good way to do it as long as you catch it. If unnoticed that could put you in hammerz71's situation. How many miles were you at when it went?

 

102k, and as stated I never had an over-heat, even when my stock radiator failed I was close to home and it never got over 220*. Most techs agree that 220* isn't enough heat to cause the heads to expand enough to drop a seat and I've seen guys with posts who lost a seat with as little as 60k on their engine and NEVER came close to running hot. But again, a strong 80% if not more who lost a valve seat did so AFTER and overheat.

I checked my stock water pump when I installed the replacement radiator and it appeared fine, not even a hint of leak even out of the weep hole. Hoses also appeared fine, but I replaced the pump and both hoses during my engine rebuild.

Despite the new pump, hoses, two bottle of Purple Ice in the fresh coolant/water mix AND the addition of a 1550 cfm pusher fan my engine still wants to run on the hot side when the A/C is on (about 210*-215*) but it will hold 195* all day long if I don't run the A/C.

I'm starting to think that this Autozone Lifetime Warranty $150 radiator just can't hold the temp with the A/C on like the $500+ Mopar dual core could. Although I know a bunch of guys with this Autozone radiator - NOBODY I can find with one is running a front receiver hitch - which blocks a good 4" of the lower radiator all the way across. The stock radiator had no problem holding it to under 205* with the A/C on, but with this added restriction the cheapy radiator wants to be a good 5-10* warmer.

I may ultimately have to ditch the front receiver but I'd hate to lose it, I use the hell out of it - not so much with my winch but I've made a couple of accessories for the front that slip right in that I use all the time - the light bar I made lives on there and I made a rod/tackle holder that I use every time I surf fish.

I've been told 215* isn't a big deal - but after losing a valve seat and having it cost me $2000 to rebuild the engine AND not knowing if that 215* caused the problem I want to try to get that temp down any way I can.

You want to keep the 4.7 as cool as possible - I'm seeing guys who lost a valve seat getting quoted as high as $4400 on the repair at dealerships!!! Thank God I could do most of my re-build and had a very knowledgeable friend to point me in the right direction at points I wasn't sure of what the hell I was doing. I probably had over 40 hours in this project (shop manual calls for 28) and this guy helped me for about 8 hours of it...

 

Sounds like my escorts 1.9 problem lol. Dropped a valve seat due to over heating in number 4. Sucks that it happens but weird to heat about it on 4.7s.