30 replies to this topic

[kit352]

So, I just took the 998 out to get petrol and maybe a mile from my house I hear a slight rap but it's pretty faint. Drive another mile and under load it's getting louder. Turn around and it's getting louder still. Doesn't seem to be clutch influenced as I drive back, more when the throttle is being pressed. It's a very metallic rap coming from the front, almost sounds like when a diesel starts struggling and just gets tappy loud. I couldn't see anything when I got home but I could hear it on occasion at idle. I left it to cool and it starts up fine but the noise is back about a mile down the road. I put the car on ramps and couldn't see much. I did notice a loose cotter pin sticking out of the drain hole on the clutch housing, no idea if it's been there forever or what's it's from but it's something I noticed.

So, facts I've noticed.
Happens when it gets warmish and gets progressively worse.
Gets quicker as rpms raise.
I am pretty sure it's coming from the clutch side. It's really hard to pin point with the motor noise. I want to say it's coming from the rocker area but I could be wrong.
Doesn't seem to make a difference if the clutch is in or out.
Gets way worse under load. I don't hear it if I'm coasting in neutral or going downhill in gear but not using the throttle.
It came on super quick. The car has been fine for years.
I did pull the carb apart just to rule out fueling since it was easy.
Valves haven't been adjusted anytime recently. I want to think that's my problem but I didn't have time to check them. My gut says the noise isn't fast enough to match valve train speeds though. The plugs looked ok.
Oil was just above minimum mark so I added a small amount to being it up to full and the noise didn't change.
The car had been sitting for a few weeks prior to this. The weather just wasn't good enough to pull it out.
Motor was rebuilt years ago. Maybe 30k on it.

I'm dreading it's the idler gear or motor bearing. I'm in the USA with it now and there isn't much in the way of parts or shops to deal with it.

Any guesses or roadmaps for me to follow while I try to figure it out? Im going to do a compression test tomorrow and get the valve cover off to check the tappets. I may try to find an oil pressure gauge locally but I don't know if I can find a tee to use to get it installed. I will dump the oil too to check for debris.

[Retro_10s]

Certainly worth checking under the rocker cover to see if perhaps you've had a valve spring let go, and/or perhaps a Collet, maybe a pushrod or cam follower? Clutch housing is easy enough to pull but you may struggle getting past the flywheel to inspect the clutch without at least raising or removing the engine entirely.

 

I think if it was my own engine i would start as you have, work from the top working down, Rocker cover off, check valves, and work downwards,.. luckily these engine come apart easily, Head can be off in no time, the issues arise if it's something deeper within.

 

Is the noise accompanied by any loss of performance? are you able to get an audio/video recording of it?

[Icey]

Fan hitting the shroud?

The split pin in the bottom of the transfer case is normal.

Edited by Icey, 07 August 2023 - 09:16 AM.

[Designer]

I had a sort of flapping noise and it turned out to be the corner of the electric's shroud catching the Alternator Pully. It was intermittent.

The attachment point from the top of the rocker cover on that side had been bent down slightly compared to the other side.

Edited by Designer, 07 August 2023 - 11:52 AM.

[burchy35]

How about exhaust manifold leaking. Either a crack in the manifold or loose nuts where it fits to the head? 🤔

[kit352]

It's been pissing rain today so I couldn't start pulling stuff apart but I did some more looking around. I'm not seeing anything rubbing or loose yet.
I have been told the noise can't be heard outside the car but inside it's very very loud. Could be a clue.
I noticed a small amount of black liquid being squeezed from the sparkplug hole on the cylinder closest to the clutch. It certainly wasn't there before. Plug looks good but I will swap it out anyway.
I didn't notice a change in power when I took it out but I wasn't running it hard and when the noise started I babied it back. I'm afraid to really push it at this point.
I will grab a video of it when the weather breaks then figure out how to share it.

[Retro_10s]

It's been pissing rain today so I couldn't start pulling stuff apart but I did some more looking around. I'm not seeing anything rubbing or loose yet.
I have been told the noise can't be heard outside the car but inside it's very very loud. Could be a clue.
I noticed a small amount of black liquid being squeezed from the sparkplug hole on the cylinder closest to the clutch. It certainly wasn't there before. Plug looks good but I will swap it out anyway.
I didn't notice a change in power when I took it out but I wasn't running it hard and when the noise started I babied it back. I'm afraid to really push it at this point.
I will grab a video of it when the weather breaks then figure out how to share it.

 

 

It's likely the noise is being transfered through the upper engine steady to the bulkhead which is directly in front of the driver. Have a look around the carb/exhaust area for loose brackets,.. and check the engine stabilisers bushes are ok,.. can you rock the engine significantly by hand?

Edited by Retro_10s, 08 August 2023 - 08:59 AM.

[DeadSquare]

I don't like the fact that it came on suddenly, and now ease off under load.

 

When something like that once happened to me on the way to London, it turned out to be a cracked rear Main Bearing Cap.

 

At a scrap yard I got a rear main cap from a Morris Minor, cut the Oil Seal bit off the back, had it hot dipped galvanized to build it up and then line bored it.

[IronmanG]

It's been pissing rain today so I couldn't start pulling stuff apart but I did some more looking around. I'm not seeing anything rubbing or loose yet.
I have been told the noise can't be heard outside the car but inside it's very very loud. Could be a clue.
I noticed a small amount of black liquid being squeezed from the sparkplug hole on the cylinder closest to the clutch. It certainly wasn't there before. Plug looks good but I will swap it out anyway.
I didn't notice a change in power when I took it out but I wasn't running it hard and when the noise started I babied it back. I'm afraid to really push it at this point.
I will grab a video of it when the weather breaks then figure out how to share it.

I had the spark plug thing on a Renault 5 turbo. Bought the car. Changed the plugs. Turns out the guy had used some sort of compound to seal them in. 1 had a tiny crack in the head so it was high pressure escaping. So as I sped up it got worse in time with the engine revs. It must have been the tiniest pin hole

[kit352]

well things have gone from bad to worse. I made a miss step this morning that has potentially added to my problems.  I should have changed the order that i did things but its too late now.  once the sun came out today i quickly checked for loose items and to see if i could move the motor.  Everything seemed fine.  I should have tried starting the car here to get the video but i did not and this is now a problem.  anyway, i decided to check the valves and all were pretty good.  I did adjust two but i didnt really have too.  so put it all together and the car will not start, it just keeps cranking and cranking. Starter fluid wont even get it to hiccup.  uh oh.  so i go about checking everything again and see nothing out of the ordinary.  I checked the valves several more times and they are all fine. I tweek one or two again but not really needed.  i do a compression test and it reads (going from the clutch over to the fan) 35,35,120,125.  Check the valves again and they are all fine and moving normally.  Crap.  

I dont think my valve adjustment caused this but im not sure.  Its possible i've been on low compression for a while and just didn't know it.  The fact i can no longer start it is new.  It has always started and now nothing.  Spark is good, Fuel is good, air is good.  starter fluid has no effect.  i think its just the two low cylinders killing me now.  And i never figured out that noise i was getting. 

Ripping the motor apart is the next step i guess.  The only thing is if its bad enough the car cant be fixed here due to lack of parts and knowledge.  It would cost so much money to get it done.  way beyond the value of the car.  At least at this point i can sell it as is and complete.  it being in pieces would make it a tough sell.  If it was just the head i needed to replace i could fly to the uk and grab one or maybe even have it shipped.  Beyond that like case or block there are no replacements here and i cant smuggle them on a flight.

 

what to do, what to do.

[Retro_10s]

Don't feel too disheartened just yet!! you've done some good fault finding - Obviously those 35's are poor results, did you perform the compression test with the throttle wide open?

 

You can have the head off in 30 minutes,.. this is your next step by the looks of things, Perhaps you will find the Headgasket has broken up, you can absolutely get a Head Gasket in the US, from MiniMania, though i appreciate your comments regarding parts availability, specialist knowledge being thin on the ground over there in terms of mechanics.

 

Headgasket on MiniMania

Edited by Retro_10s, 08 August 2023 - 07:51 PM.

[kit352]

I ran the compression tests several ways just to verify. It actually ran slightly less when I had the two bad cylinders spark plugs removed. No matter what I did those two were always low and the other two high.
I think 8 actually have a head gasket in stock here. I loaded up with spares when I was living in the UK, I just don't have bigger parts like heads or pistons. If I need a new head it's definitely coming from the UK. It's thousands here for a crap CAM head.

[Retro_10s]

I ran the compression tests several ways just to verify. It actually ran slightly less when I had the two bad cylinders spark plugs removed. No matter what I did those two were always low and the other two high.
I think 8 actually have a head gasket in stock here. I loaded up with spares when I was living in the UK, I just don't have bigger parts like heads or pistons. If I need a new head it's definitely coming from the UK. It's thousands here for a crap CAM head.

 

Keep us up to date with your findings, and good luck!

[bpirie1000]

Dizzy cap retainer clip?

[kit352]

so it is indeed a blown headgasket.  I have about 8mm missing from between the left most 2 cylinders.  The tear down went better than i had expected.  I left the rocker pedestal in place and just undid the 9 perimeter bolts as described in the manual, i did pull out 3 of the front studs but i dont think its a big deal. i will lock tight them in when i reinstall. I had to unclamp the header so i could push it out of the way of the studs.  

The head looks ok so i think it was a recent blow.  There is a fair amount of missing metal around the coolant tubes and i am not sure what i can or will do about that.  There is enough left to clamp the hoses but not by much.  The valves and chambers look ok but im no pro.

The pushrods might be worn.  The mushroom top of a few of them can not pass through the head while others can no problem.   I don't know if that is a sign of wear or if its just how it is.  I realize the pushrods would be inserted from the top so i might just be over thinking things.

 

Can anyone theorize why i was hearing the knocking noises prior to the car dying?  Is that a sign of a blown headgasket?  Any confidence i could get in that would make me spending money on head repairs a lot easier to swallow.