Ford 4.6 Timing Chain Repair

Overview

This is not a complete "how to" writeup on Ford 4.6 V8 timing chain replacement. This is a collection of pointers on doing the job on a 2002 Ford Explorer, based on my experiences. There are lots of really good YouTube videos showing the finer points of the job.

Symptoms, Diagnosis and Damage

The engine developed a slight "diesel" sound when hot and accelerating. Within 2000 miles later, the engine developed a rattle when idling hot. I replaced the serpentine belt tensioner, belt and idlers as the tensioner was shot. I did this mostly to make sure of the origin of the noise. When in doubt, you can always pop the belt off and run the engine for a short while.

Since the noise continued, it was clear that the chain tensioners and guides were likely shot. I waited an additional 1000 miles before tearing it down. My point being that timing chain issues are very forgiving with the 4.6 V8, but eventually the slack will be great enough to jump teeth, possibly destroying an engine.

The following pictures show the damage to the timing tensioners and guides after 160,000 miles. The tensioners are fully racheted up in an attempt to make up the slack in the chain. The tensioners and guides must be replaced. The chains showed no obvious wear, but they've certainly stretched some at this mileage. The sprockets show minor wear, but since I changed the chains, I chose to change the sprockets as well.

Left-side damage close-up

Left-side damaged parts

Right-side damage close-up

Right-side damaged parts

Flushing and Clean up

I suppose it should be obvious that grinding those guides down to the metal means that metal shavings get into the oil.

Metal grindings on a timing chain

Oil Filter Adaptor

Oil flows from the oil pump and enters the oil filter around the periphery. The oil flows through the filter element and then into the main oil passages through the center port of the filter. The side port from the oil pump can be used to back flush the pump and pickup. The center port can be used to flush the main oil passages.

I chose to use a Harbor Freight weed sprayer and a gallon of odorless mineral spirits I had available. Obviously gasoline is far cheaper, but it is also stinky. After removing the damaged parts, I drained the motor oil and removed the oil filter. I poured the oil into recycling containers, cleaned out the drain pan and placed it back under the oil pan - plug removed. I then used the sprayer to hose down the valve train and front cover area until spotless.

After I was happy with my initial cleaning, I took my air compressor and blew out the oil passages accessible from under the chain tensioners. This pushed everything out of the valve train oil galley. I removed the right-side rear cam bracket to blow that galley since the right side typically has the least oil flow. The oil blown out was pretty clean to feel, but when examining the cam bearing caps, I could see metal damage. Not enough to cause a failure, but it was there. Filters aren't perfect.

I checked the collection in the drain pan and found minor amounts of very fine metal shavings. Disturbing, because I'm an engine neat-freak, but not enough to damage the main bearings. I dumped the drain pan, cleaned it out and put it back under to collect the next step.

Using the HF weed sprayer, I blew mineral spirits back through the oil pump to back flush the pickup. Then I hosed out the oil pan from the front cover as best as possible. Checking the drain pan revealed more very fine shavings.

I know that most dealerships have a flushing machine that attaches to the oil filter. This flushing is important and I wouldn't take a vehicle to someone who isn't setup to flush the oil passages.