FYI - SOHC System

[Yardsale]

 

[swshawaii]

Thanks Yardsale, great article. My only question is this quote. True or false?

Fortunately, the 4.0L SOHC is not an interference engine so a timing chain failure won't bend the valves.

 

[Yardsale]

From further reading, I believe that it is false. I don't now remember where, but I saw one photo showing valve marks on a piston; they were minimal, but they were there.



As is always the case, if one suspects a timing chain issue, drive it minimally and get it diagnosed ASAP.



Edit: Check link.

 

[Richard L]

Amazing how hindsight is always 20/20 :grin:



It's a shame that consumers could not be warned of the possible consequences of this SOHC design before they invested money in buying vehicles.



Ford as well as other auto makers have deliberately designed vehicles with defects or flaws that they appear to be "Designed Obsolescence".



Ford was known to do this way back in the 1960's when they made the oil drainage holes in the cylinder heads of their V8's too small. This resulted in much of the oil being retain in the cylinder heads causing valve seal leakage and starving the cam and crankshaft bearings of lubrication.



My question is why was this obvious engineering defect not mentioned when the SOHC 4.0 L engice was introduced????:btddhorse:



I would think that Ford engineers knew this was a potential problem :banghead:



...Rich

 

[Greg Bosin]

Good info!

 

[Igor Smetaniuk]

Hey Yardsdale,



I'm on my 2nd high mileage motor - did you have to remind me of this? :-(



I have to change my thermostat housing so I think I better get a new front tensioner while I can access it and change it out too.

 

[Yardsale]

You could do that, and they're not too expensive, but it can be done without removing the housing (the bolts cam be removed such that the housing can be moved for access). If you don't have a problem, and particularly if your has the "newer" tensioner in the front (with longer exposed portion), maybe wait until there is a problem.



I have almost 250,000 miles on the original engine with no timing chain noise, so far ...



P.S. You're welcome (I think).

 

[Mickey Luis]

Other than the wrong info regarding "4.0L SOHC is not an interference engine," I think it's a very good informative article. While reading the "comments" regarding the article, I came upon the following comment.



"By the way, I have a 2005 Ranger 4.0L 4x4 with 107K. It developed mis-fire issues a month ago that were finally diagnosed as a sticking exhaust valve on #3 cylinder. According to a local machine shop, 4.0L engines are notorious for this problem, the worst being cylinders 3 and 2 (right bank)."



I have never heard of this problem with the heads and sticking valves on the first bank (1,2,3). Anyone have any info on this whether this is valid or false info. The reason I ask is because I have a '03 4.0 with a skip I'm chasing. I'm not trying to steal this tread, thanks.

 

[Yardsale]

The TSB concerning the intake and exhaust valves (Ford TSB No. 02-3-2) applies to the 4.0L SOHC engine only (SOHC and DOHC 4.0L engines were offered during the 2000 model year). Affected vehicles set a DTC P0300 or P0301. The misfire must occur at an engine speed greater than 4800 rpm (consult the freeze frame data). This type of misfire (and the resulting DTC occurs under heavy acceleration because the exhaust valves may hang open slightly.

Article link below.

 

[EddieS'04]

This info, also from some of the problems in the past from our members. Makes me question the integrety of the valve springs. That ford in colonge engine plant are using. With all the $$ shaving and having components contracted out. Is there a QC problem with the metalurgy..in the springs?

Just a thought..........

 

[Yardsale]

Perhaps it's not the valve springs. Whatever the cause, there are plenty of engine designs that don't have this problem (and a bunch with no defect pattern).