Intermittent Valve Tap -- V6

I own a 2001 S-10 V6 with about 50K miles. Well maintained. Last week, after sitting about 4 hours, I started the truck and heard what sounds like a valve tap. Almost like one of the lifters was not getting enough oil. Pretty loud and coming from the driver's side of the engine, closer to the firewall. Shut off the engine. Checked the oil. It was OK. Started back up and tap was completely gone...for about a week.

Again today, after sitting about 4 hours, I started it and heard the tap again, this time a little louder (is now a little colder). I drove for a few blocks. The tap increased with engine speed and sounded like it was accompanied by the sound of a bad v-belt (if it had one). Again I stopped, waited about 2 minutes, started, and the tap was still there. Drove a few more blocks, stopped, checked oil, OK, waited about 5-10 minutes, started the engine and now completely gone?

Very strange. It going away completely has got me thinking it might be electronic. I would think a lifter problem would be consistent and would quite down with more RPM's.

Much appreciate any ideas??

A mechanic's stethoscope would tell you if it was a lifter for sure.

If it is a lifter there is a small chance that doing a crank case flush will cure your problem

I'll pick up a stethoscope. However, are you aware of this s.b. http://www.acdelcotechconnect.com/pdf/tsb/tsb_03D-159.pdf

Any thoughts on Marvel Mystery Oil?

I'm not suprised about that bulitin, GM doesn't believe in fuel injection cleaners or anything else for that mater.

Since it's your own truck you get the final say in all the maintance.

In my opinion flushing out the crank case removes all the metal shavings, and other garbage from the motor that a plain oil change doesn't remove.
This garbage would otherwise build up and start to wear parts out prematurely.

You have to remember that Chevy makes most of their money on new car sales, and if you truck wears out 100,000 miles faster they have a better chance of selling you a new car.

Good points. My father would flush his 68 Galaxy 500 (302 cid) every third oil change. When I inherited it, it had 140K miles on it. Drove it 'till 180K and sold it. Still ran good. Not bad for a Ford motor.

Any recommendations on the motor flush. Seen Snap and Gunk in the auto parts store.

I'll tell you what I use, but it's a little expensive.

I drain the oil, and the filter, put the old filter back on.
Add 4L of Diesel, and idle the motor for 5 - 10 minuites.

Then I drain the diesel, change the oil filter... add the oil and I'm done.

I don't think that those STP type flushes are as good, but they get the job done. Plus they cost a couple of bux less.

Some additional thoughts:

Your oil filter has an anti-drain back valve in it; some are better than others. The drain back valve keeps oil from back flowing through the filter from the upper areas of the engine back into the oil pan. The AC Delco, Purolator and NAPA filters have good valves; Fram filters have garbage in them. Given the cooler temps these days combined with a leaking drain back valve, there's a good chance the oil is not getting to all parts of the motor as quickly as it should. Also, the recommended viscosity of oil for the 4.3L is 5w30.... if your running heavier oil then this may also contribute to a slow flow initially.

If this were my truck, I'd try doing an oil change using the 5w30 and an AC or Purolator filter and see what happens.....

mike

Sector95, I will give that a try, hopefully tomorrown, and let you know. Really don't want to do a flush in case I have a damaged bearing. By the way, I only use AC Delco and 5W30 oil. Been using plain Castrol for about 30 years, however, last oil change I used their synthetic blend.

A little concerned it could be a bearing. It's a tap, but a pretty loud one. Seems to quite down as it warms up.

I don't know what that oil for high mileage engines is about, but it might be an idea to look in to.

Sector95, I will give that a try, hopefully tomorrown, and let you know. Really don't want to do a flush in case I have a damaged bearing. By the way, I only use AC Delco and 5W30 oil. Been using plain Castrol for about 30 years, however, last oil change I used their synthetic blend.

A little concerned it could be a bearing. It's a tap, but a pretty loud one. Seems to quite down as it warms up.


Well. unless you've gotten hold of a bum filter it sounds like maybe the filter/oil aspect can be ruled out..... I'd probably change the filter anyway just to make sure.

IMHO, synth blend oil is just a marketing scheme to seperate you from more of your moolah. Look on the bottle, it never tells you what percentage of the oil is synthetic and what part is dino.... none of them do. Me, myself and I would go either full synth or plain dino then you'll know (pretty much) for sure what your getting.

Gauges.....if you've got an oil pressure gauge..... what kind of oil pressure are you showing when you start?


I'm not usually a fan of oil additives but if swapping out the filter doesn't cure your tapping, try adding a quart of Marvel Mystery oil or a double dose of detergent additive to the crankcase and see if that helps.

Typically, a bearing is a dull rapping sound coming from down low in the block. If the engine is making a lighter, tapping sound then it is probably a lifter that has collapsed from a temporary lack of oil pressure.

Additives are usually just 'snake oil' from what ive seen. The only thing ive ever used to clean anything on an engine that was worth the money was sea foam. it works everywhere in an engine. Its an intake cleaner, fuel system cleaner and it cleans gunk out of the engine fairly well. I use it through the gas tank every 15k or so(1/2 can). i clean the intake with it every 15k or so (1/2 can). i run it thru the oil every 3rd oil change (1/2-3/4 can). when i run it in the oil i put it in there for the last 200 or so miles before my oil change and the inside of my engine is spotless. id still love to pop the oil pan off to see what it looks like but im guessing its giong to look just like the inside of my valve cover/head. I was convinced after putting a very carboned junkyard engine in a toyota. it smoked to high heaven and along with a fresh oil change i was told by my boss to dump a can of it in there and let it run for a while. it ran for 2 hours and i shut it down for the night. came back the next day, started it up and it still smoked. i drove it for about an hour and effectively cleared about a 15 mile area of its mosquitos. the other 20 miles were clear sailing. the thing went out the door after another oil change and is still running great. its got about 50k miles on it and i had to put an oil pan gasket on it. i checked inside the oilpan and it looks like it was nearly new, but well maintained. a very different look tahn when we got it in. seafoam loves to eat carbon and sludge that is related to oil and fuel. give it a try.

Sector95. I believe you are right. Semi-synthetic is like Columbian Coffee, unless it says 100%, who knows. However, around here lately, the semi synthetic is now only 20 cents a quart higher in price, so I started buying it.

PRESSURE: It's 30 degrees outside, and on start-up, it is pushing 60lbs steady. I didn't let it warm up, but in the past, when warm, usually pushes 40lbs. If I decide to change the oil, should I let it warm up? Or maybe just quickly change the filter?

TAPPING: Sounds as if it is down low. Stuck my head under the radiator, and was just as noisy down there. Hard to say if the tap it is dull or not. Like I said before, it sounds just like a normal valve tap, but about 100% louder. Could be this particular engine.

QUESTION: If I decide to bring it to a shop because I think it has a bad bearing, would it be safe to drive about 10 miles? If I need to tow it, would it be safe to run a short distance out to my street?

Everyone, thanks for your thoughts and suggestions.

Sector95, changed the oil and filter today.

The drain plug on this engine has a magnetic tip, there were no metal particles on it. There were no metal particles in the drain pan. There was no metal particles in the oil filter.

Added Castrol 5W30 dino oil and new AC oil filter. Still tapping.

Put a stethoscope on different parts of the engine. The only tapping I hear is when I put the scope up to the driver's side exhast pipe, just below the manifold (Vavle covers are plastic)

Does this rule out a bearing problem? If so, must be either a collaped hydraulic lifter, or clogged lifter. Also, noting that it is harder starting.

I change my oil every 5K miles, but do you think my last change with synthetic loosened something up?

I don't thyink that the synthetic would have loosened anything up causing the problems.
If it did that's probably a first.

No metal shavings is a good thing usually.

All that I can sugest now is try a compression test in that one cylinder anyways, and possibly all.
A compserrion test should show you if the lifter has colapsed through lower compression

All,

Went to the auto parts store today looking for an engine flush (found Sea Foam, found something called Gold Eagle Oil system flush that said it was just detergent, no kero, etc..) There I ran into a mechanic, who, graciously, offered to listen to my truck.

I started it and he immediately identified it as a valve tap. Asked a few questions and offered the following (as we were talking the tap simply went away).

1st, he said that the 4.3L engine on the S10 is not a good breather. Whatever that means. Asked me if I had let it sit a while. Answer yes. My kids are away in college and I have been driving their cars and letting the truck sit.

Here is what he said to do:

Run it every day, change the oil often, very often. Eventually the tap will cease, and whatever you do, no additives, no flush. Just keep changing the oil, about every 1,000 miles. Hmmmm.

To me it sounds like he's very old school, which isn't bad in a lot of ways but not what you need now to get your truck running right.

I wouldn't trust this link %100 but it'll give you something to think about
http://www.auto-rx.com/

OverBoardProject. Thanks for the link. Read their claims, then I looked up and read their patent on the PTO website. Pretty interesting. Overall, pretty costly.

However, I think I am going to try some frequent oil changes and see what happens (I too am old school). I will let you know.

I'm old school as well, just not Dinosour school.

I've come to reilize that some additives are snake oil, while others work good.
Good luck with that.

Just thought of something that might work without usind chemicle additives.
If your truck uses oil add some ATF fliud shortly before your next oil change. ATF fliud is one of the best penetrating oils out there, it just takes longer than the new ones.