23 replies to this topic

[MIJ]

My engine has developed a tapping noise from what sounds like the rear of the block. The head gasket has just been replaced (noise was there beforehand) with brand new rockers and all valves set to correct clearances. The noise isn't consistent, it can be driven for two miles running quiet then all of the sudden it will start to tap. Then when it appears it stays but comes and goes and is very random. There is no consistency. The car itself runs fine, no power loss and runs smooth apart from this tapping. We have tried different rocker covers (standard and big alloy one) and still no difference. We have run the car without any cover and the noise is still there. When we took the pushrods out for the head gasket change we noticed one rod has scoring on it, unsure how or when this happened, which leads us to suspect a possible cam follower problem? But are a bit stuck as to why the noise doesn't happen all the time.
Any tips or ideas on what to try would be greatly appreciated. Thanks.

[sledgehammer]

sounds like a weak / bent push rod

 

as they sometime spin a bit , they knock on the hole , when they move around a bit the noise goes away

[pusb]

I had an exhaust leak once from the manifold to downpipe joint.
That caused a tapping sound from the rear of the block.

[Retroman]

Where was the scoring on the pushrod ?  What was it like ? how many cc engine ?

[MIJ]

Scoring was lower down on the push rod, 1275 mg metro engine

[Retroman]

I think Sledgehammer is right its probably a bent push rod.

 

They do spin slowly and the scoring sounds like its touching the hole which is the noise.

 

It needs to be replaced, and can be done without disturbing the head

 

Rolling a push rod on a flat surface will show you if its bent

[MIJ]

Hi
We have replaced the push rod, still the same problem. The one that came out wasn't bent but we tried another just to be totally sure

[Retroman]

Could you post a video of it ?

 

Is it a standard engine? how many miles ?

 

Has it had a rebuild / new cam / followers ?

[MIJ]

I will try and get a vid but no very tech savvy
It's a mg metro running std cam, 1.5 rockers (brand new). We bought as a engine that came out of a car that had done 9000 miles so not mega mileage so bottom end was left and med head fitted. Have also noticed lately it's running richer, don't know whether coincidence or not. Took it round the block earlier and the noise comes and goes, it is not consistent in fact at one point it was run extremely quiet and smooth, then it starts again. It also runs fine, revs freely, no coughing or spluttering and pulls well.
Bit flummoxed

[RooBoonix]

Check that the rockers aren't hitting the rocker cover (take the cover off and see if the tapping goes away)

[MIJ]

Thanks. We have tried that, no luck!

[MIJ]

We are going to replace all pushrods to try it

[cal844]

Could the timing be out slightly for the new spec?

I'd also be checking the fan isn't fouling on anything

[Retroman]

mmm

Should not be any 'noises' on such a low mileage motor

 

Are the 1.5's the solid spaced type ?

 

Are the end rockers 1 & 8 sprung loaded ? ....its just a thin spring washer which pushes the rockers 'in'

[MIJ]

https://www.minispar....aspx?pid=34870
These are the rockers fitted. We set the gaps to 15 thou originally and as a test increased the gap slightly. It didn't elimate the noise but it wasn't as bad. When we take the oil cap off the noise increases in loudness so is definitely from around that area.
Also checked the fan etc, no hitting or fouling.