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Car Forum / Chrysler Cars / February 20053.3L V6 - What if I ignore timing chain rattle?
I have a 1990 Dodge Grand Caravan with the 3.3L V6 engine and 130,000 miles on it. I hear a a rattling noise at idle which goes away as the engine speed is increased past the idling speed. Per another thread, it was basically decided that it is likely the timing chain. My question is what if I ignore it? I know at some future point it will break (any thoughts as to how much further down the road?) but aside from the rattling noise, is there any reason I can't just ignore it? Does the rattling chain damage anything else (timing chain cover?) When the chain finally does jump/break, will it damage anything else? Is this an interference engine / will the valves be damaged? Thanks, Eric Kotz newsgroups@erickotz.com Normally an 1/8 of an inch stretch of a timing chain is considered worn out. If the chain is exsessively loose it may cause the cam sprocket teeth to break and cause problems. However there are some on here that let there customers wait untill the chain breaks before replacing em. I believe in preventive maintenance. Glenn Beasley Chrysler Tech > I have a 1990 Dodge Grand Caravan with the 3.3L V6 engine and 130,000 > miles on it. I hear a a rattling noise at idle which goes away as the [quoted text clipped - 9 lines] > Eric Kotz > newsgroups@erickotz.com Well, I know the chain is worn, I guess I'm asking what is the potential damage to the engine when it finally does go? > Well, I know the chain is worn, I guess I'm asking what is the > potential damage to the engine when it finally does go? Chain-timed engines are almost always interference types. If the chain does jump or break, you'll at a minimum bend a few valves, at worst snap off a few valve heads and maybe knock a hole in a piston or cylinder head. 130k is pretty short life for a timing chain assuming both cam and crank sprokets are metal (most are nowdays, though back in the 70s a lot of engines got nylon cam gears to reduce noise and they generally wore out in less than 200,000 miles). But if its rattling, its probably best to replace it. I've always wished there was some list somewhere for reference as to which engines "bend valves" (interference engines). You say that "almost all chain-timed engines are interference types." I'm curious as to why that would be. Are pretty much all belt-timed engines OHC? And if so, how would that figure in to whether they're interference engines or not? > You say that "almost all chain-timed engines are interference types." I can't imagine who told you this, but it must be one of the disreputable types in my killfile. It's not so. The comment about all chain timed engines being interference types was from a poster just a few posts before mine. And that would be nice if one could automatically know if it was an interference engine just by determining if it used a timing chain vs. belt. I had never heard that either, but it piqued my curiosity in that so many OHC engines are belt timed while pushrod engines are chain--two distinctly different types of engines. Meanwhile, some engines are interference types while certain others are not, but I was never sure why that was or what made the difference. So anyway this got me wondering if one of the main criteria for whether or not an engine is an interference type is whether it's OHC or pushrod. Given the catastrophic damage an interference engine sustains from a failed timing gear, why are these engines not deemed undesireable and thus phased out or redesigned (since so many other engines are non-interference & provide satisfactory performance)? Because if all other things are equivalent, interference design engines can generally produce higher power output. How many consumers actually know to ask the salesperson if the engine is an interference or non-interference design? (versus) How many ask about the engine's output in horse power? If the consumer actually knew to ask and figured in the timing belt, water pump, etc. replacement cost every few years then in my opinion there would be much more demand for chain driven, non-interference engines. Also, with regard to chains versus timing belts, about all you can really say is that chains generally last longer and require less maintenance during the engine's useful life. A belt is generally easier to change since it does not require complete access to the internals of the engine, but can still be very costly since you need to remove all the periphery, covers, etc. to gain access Bob > Given the catastrophic damage an interference engine sustains from a > failed timing gear, why are these engines not deemed undesireable and > thus phased out or redesigned (since so many other engines are > non-interference & provide satisfactory performance)? > So anyway this got me wondering if one of the main criteria for > whether or not an engine is an interference type is whether it's OHC or > pushrod. No. Many OHC engines ARE interference, and there are a number of pushrod types that are not. I was commenting on the fact that *most* of the 60s-80s chain-timed Mopar pushrod V-type engines are interference engines. Interference allows easier optimization of the combustion chamber shape, keeping an engine non-interference puts a minimum piston-to-open valve clearance constraint that either forces a lower compression ratio or requires big valve reliefs in the piston, which can affect combustion dynamics such as detonation. Thats why today you see more and more interference engines of ALL types (OHC, pushrod, belt-timed, and chain-timed) because of the requirements for better and better combustion control to meet emissions requirements. > today you see more and more interference engines of ALL types (OHC, > pushrod, belt-timed, and chain-timed) because of the requirements for > better and better combustion control to meet emissions requirements. I don't completely buy it, and there are counterexamples. Subaru, for instance, reworked their 2.2, 2.5 and 3.0 litre engines in 2000 to make them NON-interference. > Date: Tue, 25 Jan 2005 10:43:55 -0500 > From: Daniel J. Stern <dastern@127.0.0.1> [quoted text clipped - 8 lines] > instance, reworked their 2.2, 2.5 and 3.0 litre engines in 2000 to make > them NON-interference. Perhaps their warranty costs were eating into whatever benefits they realized from the interference design. My understanding is that valve reliefs in the pistons provide places for hydrocarbons to "hide" from the combustion process, resulting in higher emissions. --Geoff >>I don't completely buy it, and there are counterexamples. Subaru, for >>instance, reworked their 2.2, 2.5 and 3.0 litre engines in 2000 to make [quoted text clipped - 6 lines] > > --Geoff I also keep reading that the sharp edges around reliefs can become detonation sources. I've also often wondered if valve reliefs are always effective. I can imagine them filling up with carbon as an engine ages, and then when the belt breaks and the valve suddenly tries to occupy a carbon-filled relief that it hasn't occupied in the previous 100,000 miles, it bends in spite of the relief. >>today you see more and more interference engines of ALL types (OHC, >>pushrod, belt-timed, and chain-timed) because of the requirements for >>better and better combustion control to meet emissions requirements. > > I don't completely buy it, and there are counterexamples. That's because its a general trend, not an absolute :-p > Subaru, for > instance, reworked their 2.2, 2.5 and 3.0 litre engines in 2000 to make > them NON-interference. And Chrysler gave up on keeping the 3.5 non-interference and made it interference in '98 (or was it '99?) when they switched it to an aluminum block and ooched the compression up again to give it 250 horsepower instead of 215. Counter-counterexample :-p Thanks to the good folks at Gates, your wish has been granted (at least for timing belts) http://www.gates.com/downloads/download_common.cfm?file=GatesTBR.pdf&folder=brochure Ken > I've always wished there was some list somewhere for reference as to > which engines "bend valves" (interference engines). > You say that "almost all chain-timed engines are interference types." > I'm curious as to why that would be. > Are pretty much all belt-timed engines OHC? And if so, how would that > figure in to whether they're interference engines or not? Chain or gear breaks. engine damage will occur AACUDA???? > Normally an 1/8 of an inch stretch of a timing chain is considered worn > out. If the chain is exsessively loose it may cause the cam sprocket teeth [quoted text clipped - 17 lines] > > Eric Kotz > > newsgroups@erickotz.com |
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