RB25det noisy lifters

[corona]

hey all need some help with my mates engine.
his got a skyline r33 with rb25det...
he recently had a bad tapping noise and took it into a mechanic to be repaired, they replaced the rocker assembly and the car came back sounding worse.... apparently they done what they could with the money he paid which was over $1000 and they would not take it back and fix it correctly.
im an apprentice mechanic so kno a little bit
so at the moment the car has bad lifter noise, i thought maybe they needed bleeding he said his driven the car around the block a few times and nothing. is there a particular way to bleed them?

i have heard these have issues with oil gallerys being blocked...

can i check this by removing the rocker cover and cranking the engine to see if oil comes up the galleries?

will a few engine flushes help clear a blocked gallery?

can i blow compressed air down the galleries if they are blocked?

any help would be much apreciated he doesnt really wanna spend any more on it.. thanks

[Dan_k36]

They do have issues with them braking the piston skirt could be that
Engine flushes can do more harm than good.
Beening a import money can go few and far between, I understand we're that mechanic is coming from, horse power equales money and being a import that's over 10 years old it's hard to quote and make sure it's fixed 100%

[jfallen]

[qoute] they replaced the rocker assembly[/quote]

RB25's don't have rockers, so it would seem they charged your buddy $1000 (or 10 hours labour for pissing in the cam galleries.) R33 RB25's run can on bucket Hydraulic lifters. The lifters are similar to those on the CA18DET (which I've got) and if dirty oil has been run through them too much they can begin to play up and make noise, (which mine also did.) The grime and shit that builds up over time with dirty oil up prevents oil pressure from filling the lifter completely and taking up the valve clearance (lash.) New lifters are available from Nissan (they're not cheap for 24 of them, I seem to remember a Price of ~$1300 for 16 CA18DET lifters.)

As for bleeding the lifters, I believe this can be done by an engine builder, but not sure about a home job. Just make sure the oil is clean and do a change after <100kms. Also as each lifter is identical you can pull them out and play swaps, remember hydraulics take up the slack, not shims. I'd say take the cams out, pull the lifters out and have a good inspection (there may be something obvious.) Then put them back in a random order if all appears well. Obviously if there is apparent damage then replace that lifter with a new one. Change the oil and give the motor a spin. Total cost will be some oil (just use cheap oil for testing and cleaning,) a filter and some time.

If the issue persists then it's either not the lifters, or you'll need to replace the lifters.

Time will Tell
Jordan

[4th surf]

Jordan is spot on here. It's only the RB20E and RB30E (T in some cases) that have rockers per-se. The DET engines run as has been said a "Direct action" Hydraulic lifter. Also if memory serves correct some have an oil pipe that sprays oil on the cam to lubricate the cam lobe to lifter contact area, the little oil holes in these can and do block up but that is nothing that a jet drill doesn't fix, but in that case you get a noise like a loose belt. I also remember the lifters being at a price of $60 to 80 each so you don't want to be doing those in a hurry.. Also this crap that they sell as petrol this day and age can and does cause pronounced injector noise that can often be mistaken for tappet noise (1UZs do this quite a lot).

How I would approach it is this and in this case while on a forum I am a qualified and licenced Automotive engineer so can give this advice from a professional standpoint.

Remove the "rocker cover" and see how "Grotty" everything looks inside. If grotty refit the cover and throw a cup of diesel in with the oil. Allow the engine to idle till hot. Drain oil. Top up with a cheap oil and idle till hot. Drain oil and replace filter, fill with manufacturers specified oil for engine or better. Top fuel tank off with 95 octane fuel or better. Add two bottles of Nulon injector cleaner to tank then drive and see what happens. There is also a product that Mitsi parts used to sell called MBL8. this stuff was magic for shutting up noisey or stuck lifters.

But.. And you need to check this.. The Nissan engines of the era were notorious by the very nature of their exhaust manifold design of ripping the exhaust manifold studs out of the head. Perhaps one here or there but they were often "Misdiagnosed" as tappet noise. The fix was to fit larger studs as they only had M8 so you had to go to M10 esp with extractors or aftermarket turbo manifolds.

[allencr]

google 'are rb25det lifters repairable?'
I got this amongst others. I can't vouch for it or even bother to read it, but the pics look nice.
Most hydro lifters are easily cleaned.
http://www.gtrpwr.com/showthread.php?t=726
Good luck.

[lexsmaz]

As has been said try & isolate that it is the lifters & if you still think it is the lifters i would pull off the cam covers & check all the valve clearances, they could run Zero clearance ? due to them being a hydraulic setup, ( google should help you there with the specs ) but what i would especially be looking / feeling for is one or more lifters that the clearance appears soft too, as in you can quite easily compresss the lifter bucket by a small amount, worth a try & the soft lifter should then be the culprit ..