VQ25DET Ticking...

[Inxlusion]

Hey guys newbie here. I've got a m35 with a VQ25DET and it has developed a bit of a ticking noise. I have heard that its pretty common for the timing chain guides to brake and wear causing some noise. I have unplugged the VCT gears with the motor running as I've heard that if they are the culprit it will stop with no luck so I am going to start by replacing the guides and tensioners though it sounds more like valve ticking to me. If it is the valves where would I start? There's so many different sizes in the valves listed, is it a case of just pulling them out and ordering the ones that match I would really like to avoid having to do that as it is currently my only car. Any help would be appreciated as the ticking is driving me nuts. Also when I cold start the car I get a horrible noise for a few seconds then quickly stops, could this be related or is that more to do with oil pressure and viscosity?

[GTSBoy]

Valves don't tick. The lifters do.

[Inxlusion]

Alright so if I was to go and replace all the lifters is it a case of pulling them out and matching up the sizes?

[GTSBoy]

VQs use solid lifters. The clearance is set with a shim**. You first need to pull the cam covers off and measure all the clearances at running temperature with feeler gauges. You then dismantle the cams off the heads and pull the shims out and measure with a micrometer. You then order new shims at the required size to obtain the correct valve clearance for any valve that had incorrect clearance. If the clearance was too large, then the new shim will need to be thicker than the old shim by the difference between the required and actual clearances.

This is not something that you can just order the parts off the net and do in an afternoon. The car will be in pieces for at least several days.

**It might be the case that the VQs don't even have a shim and they just use graded bucket (with different thickness tops on them). In which case, in the discussion above, just replace "shim" with "bucket".

[Inxlusion]

Yeah sweet thanks for that mate first car ive owned with solid lifters so i have 0 idea. from the catalogue they are a separate shim that sits on top. Under the listing I have multiple size options for both the lifter itself and the shims, if i was to replace them lifters would that be a case of ordering the same size or use that to reduce the thickness of the shims in there or just get the same size and buy shims to suit

[GTSBoy]

  On 26/05/2023 at 1:44 AM, Inxlusion said:

if i was to replace them lifters would that be a case of ordering the same size or use that to reduce the thickness of the shims in there or just get the same size and buy shims to suit

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I have no idea. There might be upper and/or lower limits to shim thickness which mean that if you need to go too far you have to get a different bucket also. Stay within the limits and keep the same bucket. That sort of thing. You'll soon work it out once measured up. Of course, once you can't know in advance until you have measured. You really need to speak to someone who has done this on a VQ to find out what the rules/limits might be.

[Inxlusion]

Alright I'll have a chat with one of the local vq guys. Thanks for all that mate I really appreciate it