Why does the engine need to be removed when replacing the timing chains?

[gnx547]

On a 98 Explorer with the 4.0 SOHC, why does the engine need to be removed when replacing the timing chains? Why can't it be done with the engine under the hood? And how many timing chains are on the 4.0 sohc? Are there 2?

 

[drdoom]

I think it's three chains, and the one that drives the cam on the passenger side, that is on the back of the engine. So that is why you have to pull the engine.

 

[2000StreetRod]

rear timing chain replacement

It is possible to replace the rear timing chain cassette (chain, sprockets, guide) with the engine in the vehicle. However, the transmission must be removed to gain access to the jackshaft rear sprocket retaining bolt and the guide assembly lower mounting bolt. This takes a considerable amount of time while working under the vehicle in restricted space even if a vehicle hydraulic lift is available. The red arrow in the photo below identifies the location of the guide lower mounting bolt. The large hole identifies the location for the jackshaft plug.

Most members prefer to remove the engine.

Camshaft timing related chains:
jackshaft to camshaft rear
jackshaft to camshaft front
jackshaft to crankshaft
crankshaft to balance shaft (4WD engines)

 

[Texan01]

Wow! I'm glad I have the anemic OHV then.

Yeah, pulling the motor would make the job easier, since in all honesty, you are 2 more bolts away from yanking the thing out, once you take the hood off.

 

[windsors03cobra]

I feel bad for anybody who had/has to go through this with this POS engine, thank GOD for the cam in block 4.0 and the 5.0. I bet half the people who had timing chain failures will never buy another Ford in their life.

The 2.0 Turbo ? In the new Exploder could be a mistake also. Lot of weight for a soda bottle displacement engine. Brave new world with high C.A.F.E. standards.

 

[Sedition]

I love the SOHC and its performance. I would buy 10 more of them before I'll by an anemic valve floater OHV.

 

[masospaghetti]

I'd be curious to know the actual failure rate of the SOHC timing chains. 10% by 100k? 5% by 200k? It's hard to tell just by anecdotal data. Ford was incredibly stupid though in designing this engine.

 

[DeepEmissions]

I wish I never read this. Ignorance is bliss I suppose. So were talking a good weekend job without Air tools??

 

[miker104]

And people ***** about changing timing belts on Subaru engines (105k interval) is much easier than timing chains. No engine removal required for TB replacement.

On a 2.5L Subaru engine you do have to remove it to change the Head Gaskets so all makes seem to have their issues.

 

[windsors03cobra]

The asians got the timing belt thing right by a long shot, some belts can be a bit of a PITA to replace but most are very reliable, pretty simple and with easy to find and align timing marks servicing them is straightforward.
Why domestic automakers have stuck by internal chains for OHC's and multiple chains in many cases is beyond me. At best most are problematic and noise and at worst kill the engine upon failure which is only a matter of time in most cases. GM has had chain problems in half the OHC motors they design. Cam in block timing chains are darn reliable and pushrods arent horrible either.

A weekend job without air tools ? Sure if you are good at swing a wrench and have pulled engine before. You will need a special set of of OTC cam line up tools which can be had used from reasonably priced I sold mine like new for $75 but if you must buy new plan to spend $150 to 200. I sold mine because I will never open up another crashed 4.0 SOHC, Scrap the junk engine and swing in another engine.

 

[Flash]

I managed to destroy my SOHC before the chains did so I'm going to replace it with another engine I have here.

The plan is to replace the chains and guides before it goes into the Ex and at some time fit a pre-oiler. Problem solved.

And if I don't tank up on Oxy and try to fill the auto through the engine oil dipstick again I'll probably never have any more trouble with it.