2016 Pentastar 3.6L Startup Rattle

[alaskanseminole]

I'm thinking timing Chain Tensioner Bleed Down?

Vehicle:
2016 Jeep Wrangler JKU
3.6L Pentastar
~90K miles
Baxter Performance oil filter adapter

Looking for some thoughts from any Pentastar experts here.

I recently had a shop change my oil pump and they used 5W-30 along with Lucas Oil Stabilizer (yuck). Since getting it back, I’ve noticed about a 1-1.5 second rattle ONLY on completely cold starts. No ticking afterward, and the engine idles smooth as silk once oil pressure comes up and doesn't do it on warm restarts.

My first thought is possible timing chain tensioner bleed down...delayed oil pressure to the tensioners, potentially caused by the thicker oil mixture (“honey effect” from the Lucas + 5W-30 combination).

A little history on my Jeep:

• In January 2025, I had a full cam shaft job (yes, both sides).
• Shop replaced all 4 cam phasers, but the original timing chains and tensioners were retained
• Since then, I’ve been doing 3,500-mile OCI intervals

Today I changed it back to Pennzoil Platinum Full Synthetic 5W-20 (w/ no Lucas additive). Obviously I won’t really know anything until tomorrow’s cold start but figured I'd ask if this sound plausible to you guys, or would you be looking elsewhere first?

 

[Slick 55]

It’s fine.

 

[Oliveoil2]

Drain that Lucas Motor Honey.

 

[alaskanseminole]

Drain that Lucas Motor Honey.

I just did. Replaced w/ 5W-20. Just waiting for over night to get a cold start test.

 

[TnT_M]

our 2014 has a little start up rattle when it sits for a few days. I think this is common. When we were shopping for the van it seemed every one on the lot did the same thing. I haven't worried about it since it seemed "normal" for this engine.

FWIW, I run 5w30 in our 3.6L

 

[KrisZ]

It's probably that Lucas stuff. Normally it's the phasers, but if you had therm replaced they should be quiet, but then again, with the thick lucas oil stabilizer, they may very well be rattling.

Mine rattles from time to time, not every cold start, but if it sits unused for few days, it will rattle.

 

[martinq]

We've heard from several members that using Valvoline Restore and Protect quieted several types of engine noises. I'd run what you have for a while and see if the noise changes / progresses. If not improving I'd change out for Valvoline Restore and Protect after 3k miles or so.

 

[NiwradND]

Mine rattles once in a while, some oil filters seem to affect it more than others also. If it was me, I would use 5w30 and change it again in 1500 miles. I'm sure that the iron numbers will come down. Jeep is a great vehicle, has Jeep had problems but they are no worse than any other vehicle and better than a lot of higher priced direct injection vehicles. Some people are getting 200,000 to 300,000 miles out jeeps with very few problems.

 

[clinebarger]

Were the 4 lifter bore plug bolts removed, Loctite applied & retorqued? Seen them loose on many Pentastar's.

 

[Skippy722]

Both my 3.6 Pentastar's would rattle like that, usually when it was colder or if they had sat for a day or more. 0w20, 5w20, 0w30, and 0w40 didn't matter it'd do it for the same length of time.

 

[alaskanseminole]

If it was me, I would use 5w30 and change it again in 1500 miles.

It's so hard to get the real deal on 5w30 vs 5w20.

Lead tech at Ancira Jeep here in SATX says - 5w20
Owner of my local offroad shop says - 5w30
Book says - 5w20
Eric at Blackstone Labs says - We don't really see a difference.

LOL

Personally, I just switched back to 5w20 and for the first time went with Pennzoil Platinum (I've always used Mobil 1). My issue was probably the lucas crap more than anything.

 

[wwillson]

I'm thinking timing Chain Tensioner Bleed Down?

Nope, the rattle is from the lifters (slack adjusters) rattling when the oil drains from the galley the lifters ride in. It takes a second or two for the oil to fill the galley and the pressure to push the slack adjusters up so the rockers are firmly engaged with the cams.

 

[alaskanseminole]

Nope, the rattle is from the lifters (slack adjusters) rattling when the oil drains from the galley the lifters ride in. It takes a second or two for the oil to fill the galley and the pressure to push the slack adjusters up so the rockers are firmly engaged with the cams.

I just had a full camshaft job 10K miles ago; New intake and exhaust cams, phasers (x4), rocker arms, lash adjusters/lifters, oil control valves, 1 camshaft position sensor, PCV/crankcase vent valve, and a new drivers cylinder head (and a Partridge in a Pear Tree).

That's why I'm struggling a bit with the idea that this would suddenly be normal lash adjuster noise unless the later oiling issue (RTV-clogged pickup/oil pump problem) somehow contributed to it.

Not to mention, doesn't my Baxter oil adapter keep the oil filter full so as to reduce drain-back from the filter housing which help the engine build oil pressure faster on startup?

 

[wwillson]

Not to mention, doesn't my Baxter oil adapter keep the oil filter full so as to reduce drain-back from the filter housing which help the engine build oil pressure faster on startup?

The adapter has zero effect on oil draining out of the lifter galley. My 3.6L in the Durango has done this since new.

 

[Hermann]

Try a different filter, with a good silicone ADBV

 

[TnT_M]

Try a different filter, with a good silicone ADBV

I don't think a filter with a better ADBV will help him. The filter even with the Baxter is on top of the engine, so most of the oil is going to drain back IMO.

 

[alaskanseminole]

I don't think a filter with a better ADBV will help him. The filter even with the Baxter is on top of the engine, so most of the oil is going to drain back IMO.

Yup.

Here's all the sludge they cleaned out last month when installing the oil pump.

Per the invoice, they cleaned the oil pickup tube, oil pan/lower oiling system cleaned, metallic sludge cleaned from drain area, camshaft position sensors cleaned, and reluctor wheels cleaned.

 

[SatinSilver]

Did it rattle on start-up this morning?

 

[alaskanseminole]

Did it rattle on start-up this morning?

sadly yes. hoping maybe a few drive cycles? Who knows. It's only those first few seconds then it's quiet as a mouse.

 

[JTK]

I'd question that whole Baxter oil filter adapter. It's likely a quality assembly, but they just seem silly to me. They do nothing to address the shortcomings the OEM oil cooler assemblies have. In my mind, having that heavy Baxter assembly threaded into it will only make the leak situation worse, plus adding to the potential of oil drain-back.