Tapping Sound on Cold Start

[Bill]

Greetings. I'm looking for some assistance on a new sound. I replaced the lifters about 500 miles ago. I'm not sure if that is related or not to the new sound, but thought I'd mention it.

On cold start, it's a loud tapping most noteable underneath the engine. The sound goes away after driving for about five minutes or so, then it sounds quite normal.

1997 Jeep TJ with 2.5 liter engine using Mobil One 5W-30 oil and Mobil One filter. Oil last changed about 500 miles ago. Engine has 213,000 miles on it. Runs strong, idles smoothly. Very quiet after driving for a few minutes.

I tried uploading a video, but the forum does not allow the MOV extension.

 

[TJ4Jim]

One of the more common issues with the 2.5 is a cracked exhaust manifold that will cause a noise until it warms up and the crack closes up due to expansion.

 

[Stockli]

Piston skirt slap?
I have a Cherokee with the 6 (I know yours is a 4) that has Ben doing this since around 200k, that motor now has about 250k on it.

Also what oil filter and weight oil you running?

 

[Chris]

My Rubcion only has 70k miles on it and it's done this forever. It only happens at start up and lasts no longer for 30 seconds. I gave up on it and just wrote it off as the lifters. I've never owned a single Jeep 4.0 that didn't make this sound at startup.

 

[Bill]

Thank you for the replies. Well, regarding the exhaust manifold gasket, I just replaced it also about 500 miles ago. The old one was completely falling apart and the engine sound was unbearable. Nonetheless, I will check the bolts for proper torque. I did torque all the intake and exhaust manifold bolts according to specification which I Believe was 23 foot pounds per boat.

 

[Bill]

Regarding the piston skirt issue, that is one that I dread! I understand that pulling the oil pan and looking for broken metal parts is the way to diagnose it. Maybe I should pull the valve cover and check the rocker arms for any play. I suppose it is possible that one of the lifters that I installed is sticky and allows a tapping sound between the camshaft and the lifter until it fills up with oil. I hope it is something that simple, because I don't want to be messing with piston skirts!

 

[Chris]

I would definitely check the rocker arms for sure. I know @mrblaine has experienced a similar sound. He told me that he put in some marvel mystery oil and it completely got rid of it. I am totally anti-additive, but he swore to me that it worked like a charm.

Food for thought I suppose!

 

[TJ4Jim]

Thank you for the replies. Well, regarding the exhaust manifold gasket, I just replaced it also about 500 miles ago. The old one was completely falling apart and the engine sound was unbearable. Nonetheless, I will check the bolts for proper torque. I did torque all the intake and exhaust manifold bolts according to specification which I Believe was 23 foot pounds per boat.

When you had the manifold off did you inspect for cracks, also I would re-torque the hardware because those bolts have a tendency to work themselves loose rather quickly. I replaced my manifold about a year ago and have re-torqued 3 times finding loose ones each time.

 

[Bill]

Thanks much. I did find one loose bolt on the exhaust manifold. All the others were OK. There was no difference in the sound after tightening though. I also removed the valve cover and checked the rocker arms for any play thinking perhaps there was a sticky lifter. The rocker arms were rock solid. I noted the comment about initial ticking which goes away after about 30 seconds, which makes sense because the oil takes about that long to be pumped up to the upper engine parts. But in my case the sound doesn't go away until about 5 minutes of running which suggests heat expansion resolving the tick as opposed to lubrication. After doing some research I decided to add Marvel Mystery Oil to the fuel. I'll do that for the next several tanks and eventually, when the oil is due for change, I'll replace a quart of the engine oil with the MMO and run it for a couple of hundred miles before changing the oil. All the reviews I read give the MMO high marks. I'm skeptical about additives so we'll see.

 

[Chris]

@Bill, I am also very skeptical about additives. However, @mrblaine is easily the most knowledgable TJ guy I've ever met, and if he says it worked for him than I'll take his word for it.

Give it a try and see if it helps. Report back with your findings!

 

[Chris]

I always assumed the ticking on start-up that is common on so many 4.0 engines had to do with oil circulation on start-up. I've owned so many 4.0 engines in my life, and every single one of them had the start-up tick. I just figured that maybe the oil systems on these things weren't the greatest, and therefore the ticking on start-up was just a byproduct of that.

Of course that's based on nothing other than speculation, but it's what I always assumed.

 

[Jerry Bransford]

Bill, your oil filter's anti-drainback check valve may have a leak and allowing engine oil to drain out of the top-end of your engine, causing a dry start. Try a different oil filer like a Fram Toughguard, Wix, AC-Delco Duraguard, Purolator PureOne, etc. which are known for good quality anti-drainback valves.

 

[Bill]

Thanks Jerry. I suppose it won't hurt to swap out the oil filter to rule out that possibility. Hey, if anyone can answer this I'd appreciate it. Regarding Marvel Mystery Oil, is there any problem adding it to the engine oil now instead of waiting till near the end of the oil change interval? The engine oil in the Jeep now (Mobil One 5W-30) only has about 800 miles on it. I was going to wait until I was ready to change it, then displace about 24 ounces of oil with MMO, run for a couple of hundred miles, then drail and fill. But would there be any issue with doing that now rather than waiting? Can I run MMO for an entire oil life cycle instead of just toward the end? Are there any adverse effects if I did it now and ran it for several thousand miles? I ask because of its high detergent ptoperties and am left with the impression it would dissolve engine sludge into the oil and running it like that for several thousand miles would be detrimental. Thoughts?

 

[Jerry Bransford]

I wouldn't run MMO until you're close to changing the oil. It thins it too much and is too much of a solvent to run it long term. Personally, I won't run any additives in my engine oil. The oil isn't causing the noise and neither M-1 nor any good quality motor oil will cause sludge if changed per a reasonable schedule.

 

[Bill]

Good advice. I'll postpone the MMO treatment until just before oil change interval. I did, however, just begin adding it to the fuel and will keep an eye on things after several tanks to see if there is any difference. Regarding the possible anti-drainback issue, I have several Mobil One oil filters and I was going to swap out the current Mobil One filter with another to rule out the possibility of a defective anti-drainback valve in the current filter. I noted the recommendation for switching to something other than a Mobil One filter, but I've never come across anything negative about the Mobil One filter, so I was wondering if there is any merit to changing to a different filter. Thanks.

 

[TJ4Jim]

I have been running the Mobil one filter for a while now without issue and the reviews have been very positive.

 

[Jerry Bransford]

I noted the recommendation for switching to something other than a Mobil One filter, but I've never come across anything negative about the Mobil One filter, so I was wondering if there is any merit to changing to a different filter. Thanks.

Mobil-1 doesn't have a lock on good quality oil filters, they don't have a lock on good quality lubricants for that matter. Not to mention Mobil-1 doesn't make their own oil filters, Champion makes them.

You're adding MMO to the fuel? Keep in mind that modern gasolines have been required by the EPA for years to have enough cleaning additives to keep the fuel injectors clean and they do. That wasn't always the case, extra FI cleaners had to be added to gasoline when FI became popular to keep the injectors clean. But it's no longer needed and those little bottles of FI cleaner additives pushed so hard by stores like Autozone haven't been needed in years.

Ask any old grizzled mechanic when the last time he saw a dirty fuel injector, as I did several times when I had a bunch of auto dealerships as customers, and he'll say it's been a long time. Ask a newer mechanic and he'll likely say 'never'. Those $199 fuel injection system cleaning specials the dealer service advisors push on their customers is nothing but $180 worth of extra profit for them.

 

[Stockli]

NAPA Gold or Wix will also have draw back valves. They are easy to find and same price or less than the others. I always run them and my 4.0 s last forever.

If it's coming from the top of the motor it could also be your motor oil has very little zddp. I run rotella T 10w/30 in dino variety and the motor stays quieter longer.

 

[Jerry Bransford]

The zinc (zddp) issue won't cause problems for a standard low-compression engine like the 2.5 or 4.0 engines. If I had an engine with a high-lift cam/high loading on the cam shaft, then I'd be looking to run an oil with more zinc. But for a normal non-hotrod engine like our 2.5 and 4.0L engines it's a non-issue.

 

[Stockli]

Good know! I always hear that the lifter shape in thes 4.0 required oils that had normal amounts of zddp. The amount was reduced for car engines to meet environmental control standards.

I love rotella in the 4.0, keeps it quiet and clean.