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4.6 timing chain question

JakePSD

Well-Known Member
Joined
March 25, 2010
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City, State
Ohio
Year, Model & Trim Level
2003 Mercury Mountaineer
I have an 03 mountaineer with a blown motor at 287,x.. miles. Timing chain failed somehow it seems. Chains and sprockets were intact, however the right side guides were all chewed up and broken, and all 4 right side intake valves smacked the pistons and broke all 4 of them off in the cylinder.

I bought an 02 for parts with a good running engine. It has 176,x.. miles on it. Before I put the motor in the 03 I want to do some preventative measures so I can have years of trouble free service. One of those things is preventing the failure that has now given me a couple hundred pounds of scrap cast aluminum.

My main question is, is there any problem with just changing the guides and tensioners and not replacing the chains and sprockets? I wanna save money where I can but don't wanna cheap out and have issues down the road. My logic says its ok, reason being that if the chains and sprockets held up to the abuse of valve/piston contact, enough to break the valves off, then they are well built enough to not warrant replacement on a perfectly good running engine.

A couple side questions, I noticed that early 02's had cast iron tensioners and metal backed guides, whereas late 02+ have all plastic construction. I'd have to assume the metal would be stronger and last considerably longer than plastic. Are they interchangeable? Can one put the early 02 (metal) parts in a late 02+ engine without problems? Would that be a good idea for longevity? What reason WOULDN'T I do that? Also, if anyone wants parts for a good price, obviously I have a parts truck.
 



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You can use the 02's. But keep in mind, they fail as well.

If the chain hasn't gone through the tensioner, there's really no need to change the chain or sprockets. Just do the guides and tensioners.
 






Are these hydraulic like the 4.0 SOHC? Is that the part that fails or the whole tensioner breaks off? Would I be better off doing the metal ones or does it really matter?
 






I needed tensioners & guides and purchased a kit a while back for $150USD and it came with chains. It has the composite tensioners though.
 






They are hydraulic, the part that fails is the gasket behind the tensioner.
 






If the metal ones are better I'd rather just buy them by themselves. After seeing all the problems in the 4.0 I'm scared of composite guides. Unless the composites are in fact better, which I find highly doubtful.

What extra steps can be taken to prevent failure of the gasket? Silicone? JB Weld (where is the sacrasm font)? Do the sprockets have to come off the get the chains over them? If so, are the bolts TTY? And is there a nice list of torque specs for the 4.6 like there is for the 4.0 SOHC?
 






My '04 OE composites went 150k before one of them began to leak. I don't personally think it's that big of a deal.
And it leaked out the plunger, pretty sure the metal ones have the same weakness there.
 






How could you tell it was leaking? And I'm more concerned about the guides being metal backed than the tesioners.
 






The guides are just a type of plastic. The tensioner arms (which are a sort of guide, not to be confused with the tensioners themselves) are metal with a "plastic" surface which the chains ride on.

When people run these engines with bad tensioners, the chains slap on the tensioner arms and eventually eat through the plastic. At this point, the chain is now "riding" on the metal portion of the tensioner arm and wreaking havoc in the oiling system. I believe in some cases with the V8, one of the guides mounting points may break as well, causing the chains to destroy them.
 






On RockAuto they have guides that have a metal backing. I'll have to look again to be sure but I'm 93.72% sure that's what I saw.
 






On RockAuto they have guides that have a metal backing. I'll have to look again to be sure but I'm 93.72% sure that's what I saw.



:D 93.72%

Just checked their offerings. All the guides they sell are plastic. They do have a metal insert where the bolt goes through to mount them.
Only the tensioner arms have a metal backing, but are still plastic where the chain rides.
 






The attached pictures are what I mean. One has plastic attached to metal, whereas the other is entirely plastic with a metal insert where the bolt goes through. I feel the one with more metal would be less likely to fail.
 

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Huh, I'd have to see them in person. From the pictures, it looks like the mounting holes are in completely different locations.

Edit, maybe not. I think the early model '02 pictures have the product upside down.
 






I just wanna know which is better. While I have the engine out of the truck I wanna do this, the water pump, and any other little things that suck to do when the motor is in the truck. I'm open to suggestions.
 






The timing on the 4.6 is fairly easy to do in the truck. Outside would obviously be great.

The metal backed version seems to be the pre 2002 design. You'll see it used from 1993-2002 in varying 4.6's.

Was it replaced due to newer fuel economy regulations, as a means of reducing weight? Or is the solid plastic piece actually an improved design? IDK.
 












Well I finally got time to work on my engine and found something interesting yet puzzling. It has the metal tensioners as one would expect on an early 02 engine, however it has the composite guides. I was hoping it had metal so I could compare quality by looking and feeling myself but that's obviously not gonna happen. So now I don't know what to do, if I should order the metal backed stuff or just stick with what was in there and get the composites.
 






This post is gonna be a bit of a small novel, but bare with me here, I may be on to something that could be of benefit to us all.

In my researching over the last couple days I did seem to get one question answered, and that is regarding the tensioners. It seems the metal and plastic ones are interchangeable between all 4.6's regardless of year and cam setup. I looked up part numbers for a 96 Crown Victoria, an 03 Aviator, an 04 and 10 Mustang (both SOHC), and 02 and 03 Mountaineer/Ex and there is overlapping years for the same part numbers. Some just seem to have switched to the plastic earlier than others. When looking at the 10 Mustang it appears that they all switched to plastic by then. In my research it seems everyone that knows these engines recommends switching to the metal tensioners as they have a ratcheting mechanism in them to keep some tension on the chain during low/no oil pressure events such as a cold start which helps reduce slapping and associated wear and also are not prone to warpage which causes them to leak oil and not provide the proper tension to the chain. So anyone doing this job, based on my research, and soon my own personal experience, I'd HIGHLY recommend switching. You can order them for an 04 Mustang and brag to your buddies that you have Mustang parts in your Mounty/Ex haha.

Now on to where my mind got even more blown than it was before, the guides and tensioner arms. Going all the way back to a 96 Vic the stationary guides have a stamped steel backing with the plastic chain ride area fastened to it. This appears to be in some of the early build 02 Ex's as well as Rock Auto shows the same part as being "to 10/02." This also explains why mine has plastic because it is a 10/02 build date, but must have been later in the month after the switch. Moving on to the late 02+ Ex and the 04 and 10 Mustang they have full plastic constructed guides with the same part numbers. BUT the 03 Aviator appears to be cast aluminum with the chain ride surface attached. Personally I like that one the most, lighter and just as strong as the stamped steel on the Vic and early 02 Ex. I just don't know if it will work. The tensioner arms are puzzling as well. All of the vehicles I looked up use the same part number except the Aviator, but they look almost exactly the same. The only reason I can think of this engine having different stationary guides and tensioner arms is because Aviators are DOHC engines. But what I'm wondering is if they are interchangeable. If so this may be somewhat of an upgrade with nearly no additional cost. The stationary guides for the Aviator are a few dollars more, but the tensioner arms are actually cheaper by a few dollars, so it's nearly a wash. I'm gonna attempt to make a little chart here to give a visual of the parts and the numbers and applications.

It wouldn't let me upload an excel file so here is a picture of it.
 

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This post is gonna be a bit of a small novel, but bare with me here, I may be on to something that could be of benefit to us all.

In my researching over the last couple days I did seem to get one question answered, and that is regarding the tensioners. It seems the metal and plastic ones are interchangeable between all 4.6's regardless of year and cam setup. I looked up part numbers for a 96 Crown Victoria, an 03 Aviator, an 04 and 10 Mustang (both SOHC), and 02 and 03 Mountaineer/Ex and there is overlapping years for the same part numbers. Some just seem to have switched to the plastic earlier than others. When looking at the 10 Mustang it appears that they all switched to plastic by then. In my research it seems everyone that knows these engines recommends switching to the metal tensioners as they have a ratcheting mechanism in them to keep some tension on the chain during low/no oil pressure events such as a cold start which helps reduce slapping and associated wear and also are not prone to warpage which causes them to leak oil and not provide the proper tension to the chain. So anyone doing this job, based on my research, and soon my own personal experience, I'd HIGHLY recommend switching. You can order them for an 04 Mustang and brag to your buddies that you have Mustang parts in your Mounty/Ex haha.

Now on to where my mind got even more blown than it was before, the guides and tensioner arms. Going all the way back to a 96 Vic the stationary guides have a stamped steel backing with the plastic chain ride area fastened to it. This appears to be in some of the early build 02 Ex's as well as Rock Auto shows the same part as being "to 10/02." This also explains why mine has plastic because it is a 10/02 build date, but must have been later in the month after the switch. Moving on to the late 02+ Ex and the 04 and 10 Mustang they have full plastic constructed guides with the same part numbers. BUT the 03 Aviator appears to be cast aluminum with the chain ride surface attached. Personally I like that one the most, lighter and just as strong as the stamped steel on the Vic and early 02 Ex. I just don't know if it will work. The tensioner arms are puzzling as well. All of the vehicles I looked up use the same part number except the Aviator, but they look almost exactly the same. The only reason I can think of this engine having different stationary guides and tensioner arms is because Aviators are DOHC engines. But what I'm wondering is if they are interchangeable. If so this may be somewhat of an upgrade with nearly no additional cost. The stationary guides for the Aviator are a few dollars more, but the tensioner arms are actually cheaper by a few dollars, so it's nearly a wash. I'm gonna attempt to make a little chart here to give a visual of the parts and the numbers and applications.

It wouldn't let me upload an excel file so here is a picture of it.

I think the bigger concern right now is your expired operating system. :eek:
 



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^good one! Lol
 






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