Engine knock under idle, Ford 3.8V6...

[2000 TAWS6]

Our 2000 Windstar SEL 3.8L (53K miles) has started making a knocking sound only while idling and only when really warmed up in higher ambient temps (over 75C).

Used Castrol GTX 5W-30 last change and sound is better, but weather is also cooler.

Is there a better choice to use? This a well known issue with these motors? If heard about the GM 3.1 & 3.4 piston slap, is this similar?

 

[OriginHacker21]

I'm not scientist but you could try seeing if a higher octane level would help. I'd dump some Chevron w/ Techron fuel injector cleaner in your tank as well.

GM is pretty famous for their piston slap. To my knowledge, piston slap usually happens during warmup only then goes away. This is the same for my vehicle 2.2L Ecotec.

 

[Nickdfresh]

It's a FORD V6 though, not GM.

 

[michaelc80]

Can you tell what area of the engine the noise is coming from? I wouldn't expect an engine to ping at idle (although I suppose it's possible).

If you can get your hands on a long screwdriver put it on different areas of the engine and put your ear on the other end (please make sure you don't put too close to moving parts). Narrow it down to which area of the engine it is-valve covers, AC unit, fuel injectors, engine block, etc.

 

[GoldenRod]

Just try some Castrol HM 5W-30. That will bump you up to 12cSt and might do the trick.

 

[ikeepmychevytoo]

My 2.8 v6 GM does the same! I don't think it is knock. Very silent at cold. It answers the higher octane and Italian tune up but doesn't go off completely. Cleaning the EGR valve quiets it temporarily. Shifting from 5w 30 to Havoline 5w 40 (~14 cSt) had no effect. However it is quieter with some oils and noisier with others.

I guess it is either combustion deposits or the hydraulic pushers. But I just can't tell which noise is which.

Lately, member Hirev mentioned something that use of higher detergent oils might accumulate magnesium calcium etc. which may become the hot points in the chamber. Well, may be I used too much fuel cleaners, even ATF on pre-BITOG years.

On an older thread from 2004 (which I can't find for some reason) one mentions that the hydraulic pushers need to bleed at a certain level and some oils (HDEO) just "clings" too much or stays there too long.

On GM's, I heard, some eccentricity problem developed at the oil pump shaft tends to act only at idle speeds reducing the pressure exclusively at idle. Pressure might be a problem with any car.

 

[Drew99GT]

Cripes, higher octane gas is not the issue with a metallic knock at idle!!! If he said he gets constant pinging sounds in 100 F weather going up 7% grades, then I'd agree.

 

[2000 TAWS6]

quote:

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Originally posted by GoldenRod:
Just try some Castrol HM 5W-30. That will bump you up to 12cSt and might do the trick.

---

How is this different than the Castrol GTX 10W-30 thats in there now?

 

[GoldenRod]

2000 TAWS6 wrote:

"How is this different than the Castrol GTX 10W-30 thats in there now?"

Regular Castrol GTX 10W-30 is thinner being 10.5 cSt @ 100C. High mileage oils are much thicker by being at least 11.1 cSt @ 100C. And in the case of Castrol HM 5W-30, it is WAY thicker by being 12 cSt @ 100C.

Sometimes motors with piston slap, benefit from thicker oils.

 

[2000 TAWS6]

quote:

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Originally posted by Ray H:
If it was a rod knock, it'd be present at steady speeds as well as coasting. If it was ignition, it would be at any speed under load. Check or replace your PCV valve. I tend to suspect, as others, that the knock's a harmless hydraulic lifter anomaly at idle. Reason? Because it goes away when you rev past idle speed. A different oil filter might have an effect, but don't expect miracles. (If you're granted a miracle, I'll graciously accept full credit.)

---

I'll try the PCV valve, but that, I think, would be a miracle too!

 

[2000 TAWS6]

quote:

---

Originally posted by GoldenRod:
2000 TAWS6 wrote:

"How is this different than the Castrol GTX 10W-30 thats in there now?"

Regular Castrol GTX 10W-30 is thinner being 10.5 cSt @ 100C. High mileage oils are much thicker by being at least 11.1 cSt @ 100C. And in the case of Castrol HM 5W-30, it is WAY thicker by being 12 cSt @ 100C.

Sometimes motors with piston slap, benefit from thicker oils.

---

Thanks, will try the HM on the next OCI.

 

[Rhymingmechanic]

Do you have an oil pressure gauge? Low pressure from pump problems could start showing up at idle speeds when the oil is hot and thinned out.

That happened to my old Pontiac that was run hard for 98K miles. Oil pressure read 5psi at idle with an external gauge (the car only had an idiot light, which hadn't lit).

I also drove a Caprice that made a strange sort of buzzing sound at idle. That was the PCV valve.

Just to clarify, when you say "knock," I think of a deep, solid sound. I would describe valvetrain noises with "tick" or "clatter." "Spark knock" is an extreme case of ping and happens under load.

 

[2000 TAWS6]

quote:

---

Originally posted by Rhymingmechanic:
Do you have an oil pressure gauge? Low pressure from pump problems could start showing up at idle speeds when the oil is hot and thinned out.

That happened to my old Pontiac that was run hard for 98K miles. Oil pressure read 5psi at idle with an external gauge (the car only had an idiot light, which hadn't lit).

I also drove a Caprice that made a strange sort of buzzing sound at idle. That was the PCV valve.

Just to clarify, when you say "knock," I think of a deep, solid sound. I would describe valvetrain noises with "tick" or "clatter." "Spark knock" is an extreme case of ping and happens under load.

---

It's not valve train, it is a bottom end sound. Oil gauge is a good idea, but I don't have one. That makes sense and perhaps the heavier oil suggested above may help this out.

 

[seldont]

The Ford 3.8 V-6 has issues with head gaskets for sure. You could have an issue of a early failure causing coolant to mix with the oil which is hard on bearings. My brother had that problem and had to replace the mains in his old 3.8 Thunderbird. It would go along with the noise being deep in the engine. If you have main bearing problems with that engine you will surely have low oil pressure. Hook an external gauge to it and drive it until it gets up to full operating temperature and check the oil pressure. If it is low check the wear on the pump gears to see if they are acored. They are mounted outside the block and fairly easy to do. If they are good suspect main and/or rod bearings to be the culprit. If the oil pressure is good??? You got me??? Maybe a wrist pin or loose piston??? The usual sound for a wrist pin is a lighter double knock type of sound when the rod changes direction at the extreme bottom or top of it's travel. You also might invest in an automotive stethoscope. I know, lots of stuff so I will quit rambling. Good luck....

 

[Rand]

quote:

---

Originally posted by 2000 TAWS6:
Our 2000 Windstar SEL 3.8L (53K miles) has started making a knocking sound only while idling and only when really warmed up in higher ambient temps (over 75C).

---

Uh 75C is 167F..., I second the head gasket problems
which were common on the 3.8 I would send your
oil in for analysis when you change it.. It may
also tell you something. Harbor Freight has automotive stethoscopes for cheap if you want one.
www.harborfreight.com
41966-1VGA
MECHANIC'S STETHOSCOPE Sale $2.49

 

[Ray H]

If it was a rod knock, it'd be present at steady speeds as well as coasting. If it was ignition, it would be at any speed under load. Check or replace your PCV valve. I tend to suspect, as others, that the knock's a harmless hydraulic lifter anomaly at idle. Reason? Because it goes away when you rev past idle speed. A different oil filter might have an effect, but don't expect miracles. (If you're granted a miracle, I'll graciously accept full credit.)