Bulletproof 4.0L SOHC?

[icthusrulz]

I have a 2002 ST (built in 4/2002) that I’m building for backcountry travel, and I want to make the motor as solid and long lasting as it can be (within reason). 140k on the clock now. Shooting for 300k.

Already on my radar...
- Manual timing tensioners
- Aluminum Thermostat housing (done)
- Failsafe Thermostat
- Regular maintenance

Am I missing anything?

 

[donalds]

If it was me I'd go pre oiler not only will it pump up your oem tensioners but it will prelube the whole engine like is was never shut down

 

[koda2000]

The bottom end of the SOHC 4.0L is very bullet-proof as is. The 4.0L OHV and SOHC use the same block and bottom end. The problem with the SOHC is in the heads and timing chain components. Using manual chain adjusters and/or a pre-oiler can protect against timing chain noise caused by slack chains and may protect against jumping time, but these do nothing to protect against broken chain guides, which are the major weak point in the Ford 4.0L SOHC engine. There are different choices when it comes to available manufactures of the timing chain cassettes (Motorcraft and Cloyes being the highest quality and cost) but the use of plastic in the chain cassettes is the weak link no matter who makes the cassettes. It is generally accepted that it is not a matter of if you will develop timing chain issues, but when. Some people here say that regular oil changes are important in protecting against timing chain problems and regular maintenance is certainly important to the longevity of any engine, but changing your oil often does not protect against broken plastic.

If it were just a matter of replacing the cassettes when they break that would be something you could live with, but the passenger side chain cassette is located at the rear of the engine, requiring the engine be removed to replace it. A stupid design by Ford to save money by using the same head on both banks. This design also requires a jack-shaft with it's own chain, guide and tensioner, plus the 4X4's use a balancer, which requires yet another chain tensioner and guide. It's a complicated engine and with complication comes more possible points of failure.

If I were building a "bullet proof" trail rig my choice would not be a Ford 4.0L SOHC.

 

[donalds]

Using manual chain adjusters and/or a pre-oiler can protect against timing chain noise caused by slack chains and may protect against jumping time, but these do nothing to protect against broken chain guides,

I disagree

My take is the rattle starts when the chains start to stretch
Then startup rattle because of a combo of stretched chains and weak tensioners causes the chain to slap back and forth breaking the weak factory guides if the chains are tight no slack I don't think they would ever even break the guides it's not a coincidence that they always break at the pivot point where the chain slaps causing the guide to pivot back and forth

Just my opinion still a bad design

 

[icthusrulz]

Thanks for the input.

I’ll be dropping the transmission soon to take care of a few things (clutch job, trans seals, rear main, oil pan gaskets), and I’ll check out the rear timing chain too. Don’t know if it’s ever been changed, but it’s never really made any noise. I’ll look into a pre-oiler.

Koda2000, I take your point (and agree) that there are better engines out there, but this is the one I have/like and I’m planning to stick with it.

Anything else I should do?

 

[MrQ]

Use synthetic oil and Motorcraft filters always and change regularly (Around 5k). Always replace tensioners with Motorcraft. Keep your cooling system clean and full and if you can, upgrade the radiator; OHV and SOHC head gaskets are not particularly tolerant of +215 °F heat. I'm not sure if your SOHC has the plastic thermostat housing, but that is also a known problem as it cracks and leaks.

 

[98Hooptie]

252K+ on my 98

 

[icthusrulz]

Use synthetic oil and Motorcraft filters always and change regularly (Around 5k). Always replace tensioners with Motorcraft. Keep your cooling system clean and full and if you can, upgrade the radiator; OHV and SOHC head gaskets are not particularly tolerant of +215 °F heat. I'm not sure if your SOHC has the plastic thermostat housing, but that is also a known problem as it cracks and leaks.

Any recommendation on radiator? It’s a manual transmission truck.

I should probably list what I’ve already replaced too...
- Thermostat housing (one piece aluminum), thermostat and all seals, including coolant temp sensors
- All coolant hoses
- Water pump
- Radiator cap
- Full coolant flush (cleaner x3, distilled water rinse x4?)
- Fan and clutch
- Rebuilt injectors (new seals, filters, and dynamically flushed. Good spray patterns)
- Intake manifold seals
- Throttle and idle air control valve seals
- EGR valve gasket and seal
- PCV and seals
- Belt, idler and tensioner
- Valve cover gaskets (didn’t check tensioners, doh!)
- Spark plugs (gapped correctly)
- Only premium oil with premium filters, and only TopTier certified gas.

All parts replaced were OEM or OEM supplier parts (Bosch, Mahle, Gates, etc), except for the thermostat housing.

Still need to replace oil filter adaptor seals (leaking), upper and lower pan seals (slightly leaking), rear main (with clutch R&R), and check out the front seals. Also may have a leak at the rear tensioner. Engine has good compression in all holes.

 

[Deleted member 352605]

@icthusrulz, a 300k sohc is possible... my sohc has 340k... only recently had a timing chain issue... good luck on ur endeavors!

 

[Fordtruckfan89]

First step for me would be a 4.0 ohv/ 5.0 swap. Not sure if manual chain tensioners would help or hurt.

 

[MrQ]

First step for me would be a 4.0 ohv/ 5.0 swap. Not sure if manual chain tensioners would help or hurt.

... I take your point (and agree) that there are better engines out there, but this is the one I have/like and I’m planning to stick with it.

 

[icthusrulz]

Thanks for everyone’s input. Hopefully with all this newfound time at home here in Washington I’ll get into the last bits of this soon.

Quick question on tensioners,when I have things opened up, is there any way to tell if the guides/tensioners are the original or updated version?

Also, if it looks like I have a set of the updated timing guides/tensioners, should I go ahead and change a tensioner if it’s leaking regardless, or is a seal replacement sufficient?

 

[MrQ]

Change it and if you can, all of them.

 

[kmartin]

As for me, I decided with my Sport Trac, if I get the death rattle, transmission needs rebuilding, engine needs rebuilding, or is 20 years old it is bye-bye Sport Trac. I hate to get rid of it now, because it is low mileage. I acquired it through marriage and my wife original intent was 15 years, and I decided to go another 5 years at the most for it, since it became just a 7 mile commuter, run some errands, and haul some brush from our house to the yard waste facility. I wouldn't mind a bigger bed, so that is why I am not thinking long term with it.