Rattly noise when cold and underload

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Arrow
Posts: 2
Joined: Sun Jul 24, 2022 12:27 pm

Rattly noise when cold and underload

Post by Arrow »

Hi all, ive just bought a Dmax LS u 016 model dualcab, now on test drive it was a bit rattly while cold, but cruising on along a stretch of rd was great, no noise, so i was happy enough and bought it due to having so much trouble with other models, and told the dmax is unbreakable, so i got hil home and its still quiet rattly when cold, takes a while to stop but when i hit an inclimb its really rattly again, drives the missus mad, i can put up with the roar from the motor but this rattle doesn't seem normal so can anyone suggest what maybe the cause, its runs great, no smoke and highway quiet as, but first start up and hills its very annoying and sounds like an old mac truck, its done 79000kms and ive been told it should have the vavle adjustment done at 80 000kms and before that should have been done at 40,000kms, ive searched the books ect and i cant find any where that says it has been done. Also mention it had towed a caravan from previous owner but with the low kms should really worry it
Anyway would that be the reason for the noisy rattle or is there something else that should be done, any help would be very grateful thanks
mydmax
Posts: 1917
Joined: Sat Oct 12, 2013 8:36 pm

Re: Rattly noise when cold and underload

Post by mydmax »

Arrow
If valves have not been adjusted to spec then the noise would be there ALL THE TIME and not dependent on throttle and injector action. Still good to have correct valve clearances. My 2011 has done a lot of cold starts and the injectors are noisey until warm. It may be a good idea to have a competent diesel mechanic experienced with CRD engines to test the injector health, leak down and individual performance of each injector. I expect I will have to replace mine soon. If it is happening when throttle applied most likely injector spray or injector action isn't good. They do make hardly any noise when cruising but under power the injectors work work harder and are noisier then. You may not be accustomed to diesel noise if petrol vehicles in the past.

EDIT.
If your engine has a faulty glow plug that cylinder will not run properly until some engine heat has developed to ensure diesel fuel correct ignition. a glow plug check might be worth doing. ie, isolate each one and multimeter test the resistance of it's heating coil. Continuity check!
Arrow
Posts: 2
Joined: Sun Jul 24, 2022 12:27 pm

Re: Rattly noise when cold and underload

Post by Arrow »

So its done 79000kms, should i get the valves checked and adjusted anyway, if that's not the problem, im thinking its maybe a thing with the 4jj and im just not use to it, other diesals were quiet compared to the dmax
Mike C
Posts: 37
Joined: Fri Dec 10, 2021 7:13 am

Re: Rattly noise when cold and underload

Post by Mike C »

Hilux's had a similar cold rattle from new about 15 years ago, it was due to defective heat treatment of injector components which were replaced under warranty by Toyota. Maybe your rattle is injector related but its not a common problem with the Dmax-well proven mechanicals are why I bought a Dmax and not a Hilux.
mydmax
Posts: 1917
Joined: Sat Oct 12, 2013 8:36 pm

Re: Rattly noise when cold and underload

Post by mydmax »

Lots of Dmax have rattling injectors after a while, noticed when cold. Mine started making rattles when cold at around 60,000km. If you look at the cam cover nuts to see if they have EVER been removed/unscrewed, ( marks on flats of hex in UNDO direction) it may reveal if valves have been adjusted. Plenty of dealers never adjust them and some only after 80,000km or so if they bother.

Pretty sure Denso make the injectors for Hilux and Isuzu so not Isuzu engineered part. Back a while same problem with similar/same concept injector. Body may be different , innards maybe not.

Injector noise which goes away when hot is an injector problem or cold air charge problem. Diesel injection knock is the result of initial uncontrolled burning of the injected fuel charge. There is always varying degrees of diesel knock sound. MORE if under acceleration. Most CRD engine give and initial minute spray to inject a limited amount of fuel to catch fire, ie, Not much to cause a knock pressure rise sound, but to light subsequent fuel injection and then continue with one or more injections ALL for the same compression/power stroke.

Regarding valve clearances. Most times they get smaller as valve faces wear slightly. With small valves, ie, 4 of them per cylinder, they have less inertia and wear the faces less as in most modern engine. Therefore longer life if cared for by having periodic adjustment. You will not hear normal valve clearances in action and even less/zilch noise if clearances are smaller because of long term slight wear. Then you may get valve failure because the valve isn't closing and high speed sonic gas screams across it's faces under combustion heat and pressure. It is best to know.
Unfortunately in the industry the lack of noise seems to indicate to the ignorant mechanics that all is well and Toyota mostly NEVER check valve clearances. Perhaps that is why you will find Landcruisers with low power and almost no valve clearances at 200,000km, some never checked at 300,000km.
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