Rattling at low rpm and high loads, timing chain rattle?

[masospaghetti]

Hey all --

I have a 2000 Explorer Sport with the 4.0 OHV and 5-speed manual tranny, 109,000 miles on the clock. When pulling away from a stop, or if I shift into a higher gear at relatively low rpm (like shifting at 2000 or 2500 rpm), it'll make a rattling noise from the engine area for a second or so. It's very consistent, pretty loud, and it has me worried. I can avoid it by shifting at higher RPM. A mechanic gave it a quick look and thought it was timing chain rattle, and he said that "was very common for this kind of Explorer". I know the 4.0 SOHC had timing chain issues, but did the OHV? What do you guys think?

Thanks

 

[Rottie]

It almost sounds like it could be the throw out bearing in the clutch. Question for the more experienced people here, can the timing chain rattle happen all at once, or does it gradually get louder and louder as more slop develops in the chain?

 

[manaen]

the OHV does not have the same history of timing chain rattle, however there is a possibility that it could still be rattling. The OHV does have a known problem with carbon buildup that will cause severe detonation problems, which will happen under high loads at low RPM. You may want to check out some of the articles on carbon buildup and the OHV engine. Does it sound like detonation?

 

[masospaghetti]

the OHV does not have the same history of timing chain rattle, however there is a possibility that it could still be rattling. The OHV does have a known problem with carbon buildup that will cause severe detonation problems, which will happen under high loads at low RPM. You may want to check out some of the articles on carbon buildup and the OHV engine. Does it sound like detonation?

It sounds different than the detonation i'm used to, but i'll definitely check into it. Is there any way I could diagnose further a throw-out bearing?

 

[manaen]

usually a throw out bearing will squeal like crazy when you push the clutch in. Your symptoms don't quite match what would lead me to believe it is a throw out bearing. Oh and btw the only way to really check it is to drop the tranny, in which case a clutch and slave cylinder replacement is in order.

BTW here is the TSB for the carbon buildup

Engine - Carbon Knock On Acceleration


Article No:
01-19-7

10/01/01

^ ENGINE - 4.0L OHV - CARBON KNOCK ON ACCELERATION

^ NOISE - CARBON KNOCK ON ACCELERATION - VEHICLES EQUIPPED WITH 4.0L OHV ENGINE ONLY

FORD:
1990-1997 AEROSTAR
1990-2000 EXPLORER, RANGER

ISSUE
Some vehicles equipped with the 4.0L OHV engine may exhibit an engine noise which may be perceived by the customer as a piston/connecting rod bearing knock. This carbon knock is heard only under load during the drive cycle. Carbon knock is a customer drive duty-cycle phenomenon that cannot be repaired with an engine exchange. This may be caused by carbon build-up within the combustion chamber.

ACTION
Verify condition. If normal diagnostics fail to correct the condition, de-carbon the combustion chamber to help quiet the carbon knock noise. Refer to the following Service Procedure for details.

SERVICE PROCEDURE

1. Use Motorcraft Carburetor Tune-up Cleaner PM-3.

2. Carbon removal:
a. Disconnect canister purge line from throttle body.
b. Attach a vacuum line to the canister purge port.
c. At hot engine idle, allow the engine to ingest 1/2 to 2/3 of a can of Motorcraft Carburetor Tune-up Cleaner. Use caution not to ingest too quickly due to potential hydro-lock issues.
d Shut engine off and allow it to soak for one hour.
e. Start engine, allow engine to ingest the remainder of the Motorcraft Carburetor Tune-up Gleaner.
f. Remove vacuum line and re-install canister purge line.
g. Road test vehicle at 3500 RPM for 2-3 miles.
h. Repeat above procedure two times for a total of three times.
i. Change oil and filter.


3. Review the customers' driving habits. The recommended drive cycle should include daily periods of engine operation above 3,000 RPM, such as a brisk acceleration from a stop position. This will break/burn the carbon off the piston head.

4. Use regular unleaded fuel, 87 Octane. Mid-grade and Premium fuels may increase the probability of carbon buildup, leading to a knock noise.



PARTS BLOCK

OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage

OPERATION DESCRIPTION TIME

011907A Remove Carbon From 1.6 Hrs.
Combustion Chamber
(Includes Time To Perform
Procedure A Total Of
Three Times)

DEALER CODING
CONDITION
BASIC PART NO. CODE
6108 42

OASIS CODES: 497000, 615000, 702000, 702100

SEE MORE INFO HERE

 

[manaen]

OH and BTW Seafoam is a great replacement for the Motorcraft Carburetor buildup cleaner.

 

[Fubeca]

Another possibility is pushrod/lifter rattle. I get the same thing - in the same rpm range from my 4.0 OHV ranger.

 

[masospaghetti]

Cool, I'll definitely give it a shot. If this is not the issue, is there a way to diagnose a "timing chain rattle" more certainly other than taking my mechanic's word for it?

 

[masospaghetti]

Another possibility is pushrod/lifter rattle. I get the same thing - in the same rpm range from my 4.0 OHV ranger.

Any way to check for this? How bad of a problem would this be?

 

[Fubeca]

I think it would be pretty difficult to truly diagnose this noise (assuming yours is like mine) without pulling things apart a little.

I can hear mine when I first start the truck just for a quick second when the engine first takes. Then I hear it at around 2500 rpm just when I'm releasing the load and ready to shift. I don't hear at full throttle under load, but just when the load starts to ease.

It is a pretty light rattle which makes me think valvetrain vs. bearings.

After reading the very end of this article (http://www.therangerstation.com/tech_library/40rebuild.htm) - I'm tempted to pull my valve covers and take a look. It may be possible to replace the pushrods and rocker arms and fix the problem.

I don't think this is a life-threatening issue. My truck has 139,000 miles and aparently has been doing it for some time (I just bought it).

 

[Kyle0614]

i second the motion for lifters thats what mine does and that's what the diagnostics said..

 

[manaen]

If it is the lifters, sometimes a motor flush (before oil change) and then add a can of lifter quiet with the fresh oil. Usually that will work if it is really gummed up you may need to change out the lifter. In the past I have had some success pulling them apart and cleaning them with a solent.

I hear of this a lot with the cheaper oils (like quaker sludge), I have a relative that swears by it and almost every engine he has had ends up with the same lifter rattle, and he even changes oil on very regular intervals.

The thing is you describe it as being at the lower RPM, and lifters usually rattle more in the higher rpm range.