Are the timing chains still an issue? I know early on it was an issue on the 3.5L Ecoboost, but I don't see many posts about the timing chains anymore.

I have a 2016 (Gen 1) Ecoboost and the truck is flawless. I'm still under the powertrain warranty and don't want to have the dealer do the chains if it isn't necessary.

I did a search, but I couldn't find much on timing chain issues on the 2015-2016 3.5L Ecoboosts.

What causes the timing chains to stretch?

 

stress and whipping under load. At lot of engines since say 2002 have used some flavor of tensioners or guides to help with chain movement. you can under load and at RPM see the chain snap back and forth inside. I need a diagram but think of the 2 sides bowing intowards each other. you would think under that much tension they would stay straight and do mostly. But under some conditions and with the velocity in there chains will give and want to bend inwards. It was thought they would flex mostly outwards but that's not always the case. ANYWAY - all the new engines have various guides and blocks so as to prevent most of this.

As far as causing the stretching - well over time either pin wear or bushing wear (the plastic bits the links ride on) allows slop in the chain's length. when it gets to be too much you loose most of the tension and it will whip around that much more. It's why it used to be said change a chain at 100K on principle. but today they can easily go for much further. better metal, better plastics, better oil, and guides help all of that.

 

I thought the Gen 1's definitely had poor tensioners early on which caused alot of failure, but secondary the problem was a single chain system which was more prone to stretch that the then poor or failing tensioners would not be able to adjust out. That was the reason the Gen 2's went to a dual chain system, to reduce the amount of overall stretch that would occur by reducing the overall individual load on one chain into two separate ones and reducing the travel path?

 

NOT a dual chain system,or at least no more so than any previous 3.5 ecoboost . It is a dual tensioner system, to take up more of the slack and extend the time before you hear the rattle.

 

https://www.f150forum.com/f118/17-3-...rattle-401441/

 

The GEN 2 3.5 Ecoboost definitely has dual timing chains. That was one of the major changes. Below is out of the brochure along with a picture


A dual-chain cam drive, with less complexity than the single serpentine chain it replaces, helps to reduce overall NVH of the 2nd-generation 3.5L EcoBoost engine.

 

Well... I stand corrected. I completely missed this when I got a peak at my truck while the dealer had it apart at 500 miles. The parts lookup does not indicate it either, but I just pulled it up in the service manual, and sure enough it is clearly dual chain. What's more interesting to me is that they got rid of the chain between the cams, so there is actually one less chain than prior versions. . Not sure why they would have done that, and in my opinion it was a mistake. This dual chain setup didn't work well for the 5.4, I wonder why they thought it was an improvement for the 3.5.
This whole thing definitely changes everything about the troubleshooting I have done and thought process of the chain noise we have been discussing in another thread.

 

 

IMO timing belts are/were a terrible idea still needing tensioners..
If they are not replaced per manufacturer's mileage they can snap in half from wear which is a BIG expensive problem if its in an interference engine.
A timing chain on the other hand will seldom break, generally last a lot longer and will give advanced warnings when they start to stretch.

I think the next major advancement for internal combustion engines will be to pitch the chains, belts and cams and go with an electrical, pneumatic or hydraulic system to open/close the valves. Of course this would have to be in a non-interference engine in case that system goes kapuut.

 

SO close to what he said.

belts were and are still used in some engines today. Interference or not when they break they do cause alot of issues. HOWEVER - modern rubbers, synthetic cords, have made belts that much better.

BUT when engine output torque reaches a certain value the belt now has to be thicker and stronger to tolerate the stress and maintain gear tooth engagement (belt blocks flex) that you end up with a heavier system than you do using a single roller chain. Then there is length and harmonics - so like I said about chain whipping the same applies to a belt system. The longer the pieces have to run (over all lenth) and the longer the unsupported spans are (distance between cogs, pulleys) then you have to secure the belt or it will vibrate and bend out of shape. Couple that with extra torque - or tension int he belt - with reaction forces at the cogs and you have have more to worry about.

So modeling says once you cross a certain point and it's a function of the engine shape and output - then you are better served moving from a belt to a chain. At this point I'm hard pressed to think of an engine on the road today over 300HP that runs a timing belt. There might be one - but not that I'm familiar with. Nissan went to all chains something in the 00's, honda did sometime after. GM only used belts on 4 cylinder models and then again went to all chains. etc etc.

Then using similar modeling you get to the point where you want to move from a single row chain to a double row - or get this all gear drive. Yes some very high power engines use a pure gear drive timing set..

Variable valve timing systems are even harder on the timing drive FYI.

As to the other point there are a number of test engines out there using everything form hydraulics to move the valves (John Tucker, you know the 3 eye'd car tucker, developed one back in the 50 - oil cavitation prevented it from reving past 1700 RPM if I recall), to electric servo's to run engine valves. One system uses a ceramic cartridge for want of a better term - it rides in intake and exhaust ports to become the port basically - and a gear motor clicks them to and from. Point is - some day you might see a engine with a different valve train - might not even have poppet valves and yes before it's mentioned the wankel rotary is a non-starter longevity wise. I know I know but mazda and but and a . . . . . thing is for the torque it can make and the efficiency it does have it costs too much to make correctly vs it's reciprocating piston counterpart.

By the time you screw around with a wankel you should just go the extra 3 steps and make a turbine. There are some specific made wankel rotary engines including some expensive personal aviation motors - but they are not popular and are often surpassed by the operation of their opposed cylinder piston counterparts.