The Wieredest Thing...

[jengis 0]

Just put new plugs in and started the engine up. Started fine but making a very loud rattle from the head, like really loud clanking! Stopped it imediately and checked everything was fine, plugs seated right and nipped up ok. Nothing I could have done just by popping new plugs in surely? So I started it up again, same noise. I was quite worried by this but let it idle as I wanted to investigate. The engine ran fine before but now sounded like the top end was knackered, like a bent valve or something!

 

All I could think that had changed was that some crud may have dropped down into a combustion chamber and was causing issues. I let the engine warm up and it was no better. Anyway I decided to ignore what sounded like a dieing engine and give it a bit of full bore accelleration to see if I could clear it out (if thats what it was). Whats the worst that could happen? After about 100m down the road and the noise was still there, but as the engine felt ok I gave it full throttle and after that the noise was gone. It now sounds quiet and runs fine!

 

Anyone had similar happen to them? Perhaps some crud was causing pre-ignition or was keeping a valve open. Any ideas as It has worried me a bit and I would like to know what the f**k was going on!

 

Cheers

[dcc 855]

:< wrong thing sorry

Edited January 3, 2009 by dcc

[Guest jon-the-sticks]

I had the same thing a few years back and it turns out that the plugs were slightly too long so the pistons were "kissing" them. If the noise has now gone, I'd get one out and have a look at it. It probably means that something's now been bent out of the way.

[Richie-Van-GTi 72 2 Cars]

As above, failing that Id be tempted to do a quick compression test for peace of mind.

[jengis 0]

Its an XU10j2 engine from 306 XSi. Plugs are Bosch super plus FR 7 DC+ and although the ones that came out were different (Champion RC9YCC) they looked the same dimensions. I even took the time to measure them carefully side by side, for that very precaution!

 

I had them out to look at them today and there is nothing to indicate any contact (does the piston really get that close to the plug at TDC?). Jon, were your plugs obviously too long?

 

I don't have access to a compression tester, but I get your drift - may be worth checking to ensure valves are seating right if (as I suspect) some crud was in the combustion chamber.

 

Although, as I said, the engine is running fine now. No missing or hesitation. Power is fine (just took it for a quick run and it did the 60-100 mph accelleration in 11 seconds, so can't be bad!)

 

Definately not my imagination either, I was getting shocked looks from some walkers passers through my yard who thought the engine was gonna blow !

 

Guess I will never know what it was for sure but not something I want to repeat.

[nick 3]

It might sound daft, but have you got all the tools you did the job with...?

 

I once left a stanley knife in the engine bay of my mk2 escort, it slipped down onto the gearbox and made a right racket. I only realised what had happened when it fell off after about a week!!

 

Nick

[davemar 16]

You have screwed the plugs in tightly enough I take it? I've had a plug come out while driving (probably due to some numpty overtightening or cross-threaded it in the past) and that made a right racket. But of course it was only running on 3 cylinders after that.

 

Or did your dentures drop down the plug hole when you were changing them?

[Grim.Badger 15]

Mine did this a couple of months ago, it turned out that I had damaged one of the HT leads pulling it off; sounded just like the pistons were hitting something A new set of leads cured it for me, although I double checked by turning the engine over with no HT leads connected first.

[jengis 0]

Mine did this a couple of months ago, it turned out that I had damaged one of the HT leads pulling it off; sounded just like the pistons were hitting something A new set of leads cured it for me, although I double checked by turning the engine over with no HT leads connected first.

 

Great answer! I like that idea!

 

My leads are very old and show signs of the insulation having worn against things in a few places. Its not great in the wet either. I have also cut part of the rubber surround off each lead as the 205 leads don't fit the narrow XU10 plug holes otherwise. It does seem likely that if if I've disturbed a dogdy HT lead causing it to arc somewhere, possibly against the head and that could cause such a loud knocking sound then that may be what has happened.

 

I was gonna buy new leads with the plugs but I didn't like Halfords prices....

[marksorrento205 80]

I was gonna buy new leads with the plugs but I didn't like Halfords prices....

 

 

You need to get yourself a Halfords trade card!!

[jengis 0]

You need to get yourself a Halfords trade card!!

 

I would probably get my use out of it. Somehow I always manage to come away with more than I went in for, usually some random tool that I will only ever use once

[Guest jon-the-sticks]

Just to answer the earlier question, yes my plugs were obviously longer. Not by much but certainly enough to see without needing a ruler. I can't remember whether it was my mistake or the guy in the shop's but basicaly they were the wrong plugs.

[Cameron 16]

I would probably get my use out of it. Somehow I always manage to come away with more than I went in for, usually some random tool that I will only ever use once

 

I know that feeling. Happens with the Snap-on van at work too.