Strange ticking noise

[iandb1970]

When I started the car when leaving work this afternoon I immediately noticed a strange, regular and reasonably loud ticking noise coming from the engine bay. Something I certainly had not noticed before. I lifted the bonnet and it was quite noticeable over the normal engine noise but I could not determine exactly where it was coming from (and not being an engineer or expert this probably would not have helped anyway). When I had the bonnet lifted a colleague walked past who asked if all was OK and before I could answer he also noticed the regular ticking noise also. It was that obvious.

As there was nothing else to do I drove home (about 30 miles) - the noise was not obvious when driving. Once home I lifted the bonnet and the noise was still there, albeit not as noisy.

The regularity I would put at about 0.75 -1.0 second but it was absolutely regular and tick describes it very well. Does anyone know what this might be and importantly whether this could be a major issue.

[Dorset Bob]

Sounds like the purge valve to me, and if so, nothing to worry about.

[iandb1970]

Originally Posted by Dorset Bob

Sounds like the purge valve to me, and if so, nothing to worry about.

Please explain further - I have no idea what you are talking about

[T-Cut]

Originally Posted by iandb1970

Please explain further - I have no idea what you are talking about

Otherwise known as the Slack Tappet Simulator (or STS), it's attached to the rear near side of the upper inlet manifold on the V6 (on the battery box on the 1.8). Both positions enable sound amplification from the solenoid operated purge valve. This is tripped on every so often to purge fuel vapour absorbed in the carbon canister fitted uner the rear end. The result is a noticable tapping sound that can scare the pants off the unwitting owner. One wonders how much those unscrupulous garages have made from it.

The documentation indicates it should only run when the engine is in its closed loop fuelling regime and the car is moving. My own observations, supported by your question, indicates it can run immediately on a cold start up. This seems to refute the closed loop requirement and the car certainly desn't have to be on the move.

TC

[iandb1970]

Originally Posted by T-Cut

Otherwise known as the Slack Tappet Simulator (or STS), it's attached to the rear near side of the upper inlet manifold on the V6 (on the battery box on the 1.8). Both positions enable sound amplification from the solenoid operated purge valve. This is tripped on every so often to purge fuel vapour absorbed in the carbon canister fitted uner the rear end. The result is a noticable tapping sound that can scare the pants off the unwitting owner. One wonders how much those unscrupulous garages have made from it.

The documentation indicates it should only run when the engine is in its closed loop fuelling regime and the car is moving. My own observations, supported by your question, indicates it can run immediately on a cold start up. This seems to refute the closed loop requirement and the car certainly desn't have to be on the move.

TC

So I have nothing to worry about or is this a job that needs doing?

[murphyv310]

Hi.
As far as I'm aware the purge valve doesn't operate on a cold engine. If you get the ticking when the engine is cold increase the revs slowly and see if the ticking speeds up, if it does there's a strong possibility you've a sticky hydraulic lifter. In that situation I'd do an engine oil flush and oil filter and change, use fully synthetic oil of the correct specification, 5W-40. That should cure the problem

[T-Cut]

Originally Posted by murphyv310

Hi.
As far as I'm aware the purge valve doesn't operate on a cold engine.

MGR say that, but I can verify that it may well operate on starting from cold. In fact I had my engine stripped down for almost a month recently and when it was finally restarted, the purge valve started immediately. I've heard it running before on a cool engine and certainly the car on tickover each time. I guess most people only hear it when stationary, which contradicts the warm engine/closed loop fueling and open throttle/driving condition described in the manual.

TC

[murphyv310]

Originally Posted by T-Cut

MGR say that, but I can verify that it may well operate on starting from cold. In fact I had my engine stripped down for almost a month recently and when it was finally restarted, the purge valve started immediately. I've heard it running before on a cool engine and certainly the car on tickover each time. I guess most people only hear it when stationary, which contradicts the warm engine/closed loop fueling and open throttle/driving condition described in the manual.

TC

Unplugging it will of course stop the rattle from it and will aid the diagnosis.

[iandb1970]

On further investigation yesterday the ticking certainly increases with engine turnover. Therefore is it the purge valve or the hydraulic lifter?

The car had an oil change about 4 months and 6000 miles ago (I will probably get another one very soon - I look approx. 6 months and 6000 mile oil changes) with some fully synth Mobil (5w40 I remember correctly) and the oil change before that was with a flush and a Millers additive.

Next question:

a) if its the purge valve is there nothing to worry about? I certainly never used to have this ticking, stationary or moving

b) if it is the hydraulic lifter other than an oil change is there anything else to do or worry about?

I am no mechanic so need the helpful information you guys give so I can then get a garage to do the work.

[T-Cut]

Originally Posted by iandb1970

a) if its the purge valve is there nothing to worry about?

The purge valve operation is a standard part of the emissions control system. If the sound definitely originates from the RHS of the upper manifold it's the solenoid valve. Use a screwdriver as a stethoscope. The easy way to prove is to disconnect the solenoid at the plug.

b) if it is the hydraulic lifter other than an oil change is there anything else to do or worry about?

The first resort would be to try an oil additive like Wynn's Hydraulic Lifter Treatment. A noisy lifter usually happens after the engine's been stripped down and put together without filling the lifters. It can be spontaneous though.

The use of a 5w/40 oil could be relevant I suppose.

TC