Rattle when starting engine after a week of sitting

I noticed after starting my 2021 Tundra 5.7L after sitting a week a rattle emerged from the engine for just a couple seconds during start up. Is it possible the hydraulic lifters drained down over a week. I am not familiar with overhead cam engines. After a couple seconds back to normal engine sounds. I had my 4Runner sit for month and started without issue. Thanks in advance!!

 

I have a 2014 5.7 Crewmax and since COVID my truck has been sitting a lot too. I’m hearing the same thing and was wondering what the noise was.

 

https://www.tundras.com/threads/rat...ruck-has-sat-for-24-hours.66239/#post-1724925

 

To summarize the other thread it’s either ac compressor gulping a bit of vapor or the lifters being noisy from a slight bleed down.

 

I read the other post. 99.9% sure from oil bleeding out of hydraulic lifters allowing lash/clearance to develop between lifters and camshaft on start-up. Translation we don't like the noise but it has zero adverse affect on engine over it life. In other words other parts of engine will wear out long before the excess lash on start up will cause issues. Before 1972 all engines had solid lifters, you set the lash/clearnace between the pushrod and rocker arm every 8-10K miles or when they got super noisy. With solid lifters you had to account for pushrod growth as the engine warmed so you had clearance between pushrod and rocker arms or lifters when cold and the clearance was taken up as the engine warmed. If their wasn't any clearance when the engine reached temperature the valve would be held open. So every time you started you muscle car it would clatter until the engine warmed or about 10 minutes. Hydraulic lifter take up the clearance automatically so you never need to adjust.

So with our engine the oil bleeds down because no back flow preventer in oil filter? who knows, but it does happen for whatever reason. Toyota didn't want design a back flow preventer so we can hear the rattle now. We hear the rattle due to the clearance between the lifters and valves stem when the oil bleeds out of the lifters over time. So assume our engines rattle for 2 seconds every day. Old solid lifter cars rattled for 10 minutes or 600 seconds every start-up. In other words one cold start on a solid lifter car sees the same wear as ours see at 300 starts assuming yours rattles 2 seconds. Mines about 1/2 second if it sits a week.

Other thread mention VVT pulley. WRONG. The VVT stands for variable valve timing. Pretty cool it simulates changing the profile of your cams for the best of both worlds torque low, power high rpms. My 2001 Lexus has it. It is modulated by oil pressure. NOTE STICK WITH OEM RECOMMEDED OIL VISCOSITY!! If not you change the profile of your cam vs what the OEM found optimium. Heavier oil is higher oil pressure so the VVT thinks you are going 50 mph when you are going 20 mph because you have higher oil pressure with the heavier oil. The only way VVT pulley goes bad is it leaks EXTERNALLY all over your timing belt. They have to leak internally or they couldn't modulate your cams. Another thing bearing clearances are designed for a certain oil viscosity. You put a 20W50 in our engines bearing will be starved. For example old rod bearings probably had .006" clearnace good for 10W40. New engines have .002" clearance so the heavier oil can pass through and keep the bearing cool.

 

The most stressed system in an engine is the valve train. High spring pressures were required in push rod style engines (GM still uses) vs our overhead cams. Last thing you want is your lifter flying off your cam at the cam peak and get valve float. (valve float happens when the lifter is launched off cam due to low valve spring pressure or broken valve spring, then the self adjusting hydraulic lifter pumps up, accommodating the clearance, problem is when lifter comes back in contact with camshaft lifter is pumped up and the valve doesn't close all the way.) So traditional style pushrod engine use valve springs set 250lbf open and 110lbf closed. I had a Roush 427R in Cobra replica it used valve springs 410lbf open and 270lb closed, very aggressive camshaft with steep lobes. I would guess an overhead cam engine uses 150lb open, 70lb closed or much less than pushrod. You don't have all the mass of a pushrod engine so overhead cam can rev higher. In the end the huge disadvantage of overhead cam engines is cost and size. They cost more and the head is much larger.

 

Thanks so much for sharing your vast technical knowledge. As a new member in the Tundra forum, I am always amazed for the incredible knowledge our member possesses.

 

You are probably hearing the timing chain rattle until the tensioner fills with oil. Its very common on overhead cam engines.

 

Timing chain tensioner is spring loaded. Never seen one pressurized by oil, if that were the case the chain would be slack when first starting the engine. Another side note oil pumps used to be mounted in the oil pan submerged in oil. Today they are mounted on front of the engine behind the harmonic balancer. Buddy of mine has a Ford Ecoboost, he monitored oil pressure on start up with Forscan (ford software) he found it takes up to 4 seconds for oil pressure to stabilize. Old submerged oil pump would stabilize in a fraction of a second. New pumps have to pull the oil up out of pan to pump suction before they pump it forward to engine. Old style just pump forward. Again an oil pressure timing chain tensioner would be non-linear with oil pressure fluctuation.

In addition as I was researching the Tundra oil pump I saw a guy remove tension on the timing chain tensioner by inserting a pin in the tensioner after he compressed the tensioner plunger to remove the chain.

 

Look up the parts list, the chain tensioner is hydraulic and supplied with engine oil, it is quite common to have this arrangement. Anyway Im out. Im not arguing with you about this. I have held these in my hand. In any case overhead cam engines do rattle on startup when they sit for a while. I have owned several overhead cam engines that have all done this. If it rattles for more than a few seconds the wear plates on the side of the cam may be worn to the point that the tensioner cannot keep up with the flex.

 

I'll add to this...

overhead cam engines have a greater flexibility in intake and exhaust port dimensions (variation in width and length, and pretty much any 2 dimensional shape you can imagine). Along with this they can get multiple valves per cylinder that can approach some large pushrod engines in effective flow area across the port.

But yes the packaging from the extra width a huge challenge.

 

Many tensioners are hydraulically tensioned with a ratcheting system for preventing slack. Ford has had this system for 40 years. Its not uncommon to have a separate oil feed to the tensioners to avoid a delay in pressurizing (if they were downstream of cylinder head).

 

Well, learned something today looks like the tensioner has spring and oil pressure "The 3UR-FE heads have the same design. They are aluminum alloy cylinder heads with camshaft housings, four valves per cylinder (two exhaust valves and two intake valves), and double overhead camshafts. The valves are actuated by roller rocker arms. The 3UR-FE engine has hydraulic lifters. The engine uses two primary timing chains for the intake camshafts. Each intake camshaft drives the exhaust camshaft by the secondary timing chain. All chains have a chain tensioner that used oil pressure and a spring. The engine can control the intake and exhaust camshaft angles by the Dual Variable Valve Timing - intelligent system (Dual VVT-i)."

This tells me if the tensioner spring is not broken the tensioner keeps tension on the chain and I GUESS oil pressure supplements. So my engine has 980 miles and 3 weeks old (2021) I doubt my tensioner spring is broke and yet I get the rattle for 1/2 second on start up if sits for days. I am still confident lifter bleeding down causing noise. I saw this on Youtube videos broken tensioner is sloppy with cover off, tensioner on other side maintained tension since spring on tension was good. So cold start up with good spring in tensioner shouldn't create noise since there isnt slop between chain and tensioner.

Video of tensioner issues is a different sound in my opinion its more of whooping, or not as sharp as rattle. Tensioner sound IMO is not as metallic.

Again in the end its not a problem.

The 3UR-FE is the most reliable and durable engine for all UR engine family. The Toyota made over 1.3 million kilometers of durability testing for this engine. In reality, the 3UR-Fe can run more than 400,000 miles (650,000 km) smoothly with regular maintenance with using high-quality fuel and oil.

But nothing is perfect and this engine too. The 3UR-FE has a problem with coking of the piston oil rings which caused high oil consumption. After that, the oil consumption increases over time. To avoid this problem, use only the recommended high-quality oil and watch the oil level. The 3UR-FE crankcase ventilation system sensor fails hugely often, and electronic throttle system ETCS-i is not as reliable as it should be. The problem with water pump is also found in this engine. Like other UR engines, the 3UR-FE has a leaking water pump with short life about 60,000 miles (100,000 km).

 

yeah there is also a second tensioner for the chain that connects intake and exhaust...

 

Toyota guys need to buy a Ford or GM. Maybe even diesel, hear about $10K fuel pumps failing, transmission failing, electronics failing, poor drivability. Only reason I know anything about cars is GM and Ford issues. I think Toyota screws us on options. My buddy brags about his 19 mpg in his GM 6.2L when not bitching about transmission shifts dislikes. Guess what my Tundra does just as good as his on MPG. He is required to use Premium which is 36% more than regular gas, sooooo my 15 mpg just turned into 20.4 mpg. Oh I don't have cylinder deactivation shit either, or direct injection or blah blah blah,

 

I run Schaeffers oil and it claims to keep parts coated whenever the engine is restarted, for less wear and tear. I noticed it alot in my 95 7.3. Really helped to quiet down everything and I go 2 or 3 months without starting it and it sounds the same as if I cranked it everyday. Now 7.3s aren't quiet by any means, but compared to Rotella and other brands I've ran before its a noticeable difference.