4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

Motor Swap - Preventative Maintenance on junkyard motor?

Old 02-06-2019
Thread Starter
Join Date: Feb 2019
Location: San Ramon, CA
Posts: 2
Motor Swap - Preventative Maintenance on junkyard motor?

Hi Guys,

I have a 2008 4.0 that I'm going to be doing a motor swap on in the very near future. I bought a 4.0 from the same year Ranger with 80k miles on it to put in.

What do you guys think I should replace on the junkyard engine before installing? I'm thinking water pump, thermostat, belts, spark plugs

Old 02-06-2019
RF Veteran
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Join Date: Jan 2014
Location: Vancouver, BC
Posts: 12,191
Welcome to the forum

Rear main seal, on any engine any time you can get to it

Spark plugs can be pulled and cleaned, look at tips to ID any previous running issues, pull out all 6 and then crank engine over by hand and listen for noises

Water pump and thermostat can be done fairly easy with engine installed but up to you.

Inspect fan belt, and spin each pulley by hand, listen for noise

Make sure to keep a record of where the engine came from, model and year of vehicle, Calif is a stickler for paper work on engine swaps, and only allows same year or newer engine swaps
Old 02-07-2019
cliffdog2004's Avatar
Join Date: Jul 2018
Location: Irvine
Posts: 327
Ron lies!

Do the water pump and thermostat BEFORE the swap!

j/k Ron

Also, clean any hose connections and use new hoses and screw-to-tighten hose clamps. The old spring type may be too worn/old and it's a few cents to replace.

Clean any exposed gasket surfaces the best you can. Most of it will be aluminum, so use a plastic scraper to get off old material and a scotchbrite sponge pad to really clean the little, stubborn stuffs.

If and when you do the thermostat, and if you take out the temp sender/sensor, replace the o-ring. The old one is stubborn to remain in its old shape and won't take nicely to reinstallation. Phantom leaking can result if overlooked.

Because my intake was removed (swapped 2008 to 2003 and the wiring harness was different), Ron had suggested replacing the knock sensor. It's exposed, meow, so why not? It's a cheap part.

Clean clean clean...

Try not to use a pressure washer. Easier, sure, and other people have and have had good results, but a lot of the time, prep time isn't taken by covering galleys and inputs and nooks and crannies...

Spray your fav degreaser (even warm soapy water) and scrub with those scotchbrite pads and/or brushes. You control where it goes and clean exactly what you are going for.

The exhaust manifolds on my donor motor were oxidized, but because those were cast iron, I Dremeled the crap off

Cleaning is a great way to see later if you have any leaks. It just looks better in that engine bay, too.
Old 02-11-2019
Thread Starter
Join Date: Feb 2019
Location: San Ramon, CA
Posts: 2
thanks guys for the replies. I hope to start the swap this week. I've added seals to the list to be replaced.
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