The infamous SOHC timing chain tensioner

[mattcc88]

Hey guys,

I've had the timing chain rattle for a while upon cold starts until a few minutes of driving. I decided to look into changing the tensioners, but upon looking around on the internet for a while, I have a quick question.

Would it be bad to replace the tensioners if I have a broken timing chain guide?

My main concern is that the increased tensioner pressure would cause a faster deterioration i.e. cause more harm than good.

2001 Explorer Sport
V6 4L SOHC
172,000 mi

Thanks in advance

-Matt

 

[2000StreetRod]

pressure vs lubrication

The first step in Ford's published rattle resolution process is to replace the spring/hydraulic tensioners. I think that's because its fairly simple and inexpensive. I recommend that the timing chain tensioner be replaced every 75,000 miles or whenever chain rattle is detected at the rear of the right head. Chain rattle usually is first detected at engine cold start because the oil has had time to drain from the timing chain components. As the tensioners age the internal spring pressure weakens and the plunger exerts less force on the timing chain. This allows chain slap until oil pressure builds in the tensioner. Chain slap accelerates guide wear. As the guides wear eventually the chain comes into contact with metal surfaces resulting in chain wear and metallic particle contamination of the oil. The metallic particles in the oil accelerate oil pump wear and can accelerate wear in engine bearing surfaces unless a high quality filter traps them. Typically the rear chain cassette lasts longer than the front cassette because upon engine start the rear cassette receives oil sooner than the front cassette.

The spring pressure in my new tensioners were not noticeably stronger than the old ones. Similar results have been reported by other forum members. Very few members have reported that installing new tensioners fixed their chain rattle. If the guides are broken the maximum displacement of the tensioner piston will not be enough to make the chain tight on the slack side. If the chain rattle is due to lack of lubrication then new tensioners will not fix the problem. After replacing all of the timing chain components with the latest improvements I still had cold start rattle due to lack of lubrication. I fixed the rattle by installing a pre-oiler.

I doubt that installing new tensioners will cause further damage to your guides. In your case, I doubt that installing new tensioners is worth the effort and expense. I encourage you to replace your broken guide(s) before a chain slips and you have valve damage.

 

[mattcc88]

Thanks for the advice. I was able to take out the rear tensioner and noticed there was no different in resistance between the old and new. I'm not in a position to be able to remove the engine to get the guides changed, so I'm hoping that it will last another year or two before causing any catastrophic damage. I returned the new rear tensioner and put the old one back in, but I'm going to replace the loudest one, the front, regardless. I appreciate the advice and wish I had read it before I ordered the parts! I'll post the results of the front tensioner when I get to it.

Thanks again!