Author Topic: It happened - zero compression on cylinders 1 & 2  (Read 337 times)

Offline John Gervais

It happened - zero compression on cylinders 1 & 2
« on: September 16, 2021, 08:39:13 PM »
I was on the highway cruising at around 65 - 70 mph when it happened, my fishing gear loaded up and looking forward to a day's trout fishing when my engine suddenly lost power, gave a short 'puff' of black smoke out the exhaust and began running extremely rough. 

Fortunately there was an offramp literally right there, so I was able to limp off onto a small 1-lane rural road and found a gravel parking lot and called for a tow back to my garage.  After I got it home, I pulled the plugs and did a compression test - cylinders 3 & 4 had 175/180psi, cylinders 1 & 2 had about 15 psi.  I only did one test per cylinder, because the results seemed pretty obvious.

The plugs didn't look too bad either, a slight greasy sheen on number 1, nr. 2 was a bit sooty, and 3 and 4 didn't look too bad at all - of course, I had driven on them to find a place to park, so I have no idea what they looked at at the moment that the engine lost compression.  But it looks like they were all firing, so hopefully the face of the block is ok.  The plugs look darker in the photographs than in reality - I haven't studio lighting in the garage.  The ceramic is very light grey, the ground electrodes are also greyish, and there's a bit of carbon on the steel.  So if anything, a tad rich after having driven at idle speed for 2 or 3 miles at the time I turned it off.

It was running strong at the time, with good oil pressure, 85C temperature and smooth as silk.  I'll be pulling the head off tomorrow (hopefully - the garage has far too much stuff in it to move around in), but I'm not looking forward to seeing the damage.
- Pave the Bay -

Offline 94touring

Re: It happened - zero compression on cylinders 1 & 2
« Reply #1 on: September 16, 2021, 08:56:00 PM »
Well that's a bummer.  Hopefully just the gasket.

Offline John Gervais

Re: It happened - zero compression on cylinders 1 & 2
« Reply #2 on: September 16, 2021, 09:13:32 PM »
I'll be happy if it's just the gasket or even the cylinder head - I haven't had the space to rebuild the 'spare' engine that's been sitting buried in the corner for the last 10 years, let alone try to pull this engine out.

It would have been a great day for the trout too; didn't even make it there, and then it started raining when I got picked up.  To add insult to injury, it was a long walk home in the pouring rain from the garage.
- Pave the Bay -

Offline MiniDave

Re: It happened - zero compression on cylinders 1 & 2
« Reply #3 on: September 16, 2021, 10:09:35 PM »
Check the block carefully, and you might need to have the head skimmed so it will hold the gasket better.

I've never had one fail between 1&2 or 3&4, for me it's always been in the center between 2&3....

Good luck, can't wait to see the pics.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

Offline John Gervais

Re: It happened - zero compression on cylinders 1 & 2
« Reply #4 on: September 18, 2021, 04:44:46 PM »
Thanks - I can't wait either...   ::)

I haven't had a chance to get in the garage yet to look at it, and it'll probably have to wait until Monday before I can start on it. 

I've been kicking myself that I didn't at least drain the coolant before I left it on Wednesday.  If the head gasket is compromised, I hope it's not weeping coolant into the cylinders...   :-[
- Pave the Bay -

Offline John Gervais

Re: It happened - zero compression on cylinders 1 & 2
« Reply #5 on: September 20, 2021, 04:21:05 PM »
It looks like I might have gotten off easy!

I can't feel any burn through on the block face and can still see the milling marks between the chambers on the head.  There wasn't any coolant in the cylinders, either.  My back is killing me right now, but if it feels ok tomorrow, I'll clean everything up and hopefully put it back together.

I can barely see any of the cylinder hone's cross-hatch marks, so this one's apparently getting a bit tired, so I will need to rebuild the spare block at some point sooner than later.

I wonder why it burned through the gasket like that?
- Pave the Bay -

Offline mascher

Re: It happened - zero compression on cylinders 1 & 2
« Reply #6 on: September 20, 2021, 04:41:47 PM »
What I assume is #1 piston is suspiciously clean and also appears to have some pitting. These are typically symtoms of lean mixture and detonation. I thought your spark plug pictures looked like lean running (one man's opinion), I usually like to see brown to dark brown. They didn't seem extremely lean but I would always like the mixture to be a little rich rather than a little lean. Worse fuel mileage, more power and less chance of detonation.

Kelley

Offline John Gervais

Re: It happened - zero compression on cylinders 1 & 2
« Reply #7 on: September 20, 2021, 04:54:06 PM »
I just noticed that myself - I'll wipe the top with some solvent and take a look with my glasses on and a magnifying glass to be sure if they're pits or only towel dust from wiping the oil from the surface, and maybe back off the timing a tad and give it a little bit more fuel.  It's an Aldon Yellow dizzy, now with 2000 or so miles on it.  But I think that this head gasket will only be a band-aid - I think I need to build a new one.

I drive primarily on the highway, and my last trip (160 miles) averaged to 33mpg.  Generally, I'm getting between 31 and 34 mpg, measured over the past 5 or 6 months, and each highway drive is a minimum of 45 minutes over 4000 rpm at highway trot, usually between 70 - 80mph.


I was able to get a somewhat better picture of the plugs after I'd limped to the parking lot and shut it down.  Not that they show what it was doing when I lost compression...
« Last Edit: September 20, 2021, 05:42:00 PM by John Gervais »
- Pave the Bay -

Offline MiniDave

Re: It happened - zero compression on cylinders 1 & 2
« Reply #8 on: September 20, 2021, 06:32:21 PM »
Be sure you check that head carefully to make sure it's flat.....
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

Offline John Gervais

Re: It happened - zero compression on cylinders 1 & 2
« Reply #9 on: September 20, 2021, 06:45:43 PM »
I will - it's one of Calver's, so I don't want anything bad to happen to it.

Are you using a precision-milled bar and feeler gauges to check yours?

I just found out that Hyacinth has a conference on Wednesday, so I'll have access to her car; if necessary I can take it to the MG racing shop and check it properly, and possibly leave it with them with my box of components (new valves, guides, seals etc.) to have it re-surface skimmed and rebuilt if necessary. 
- Pave the Bay -

Offline MiniDave

Re: It happened - zero compression on cylinders 1 & 2
« Reply #10 on: September 20, 2021, 06:58:46 PM »
Anytime I have a head that needs a valve job I just have them shave the head a few thousandths - it's not enough to change the compression ratio much and it makes sure the head is flat and will hold the gasket. I've never had one fail yet....

Do you have ARP head studs? If so, you need some of their special lube  - and be sure to torque them in three rounds, 30, 40 and 50lbs.
« Last Edit: September 20, 2021, 07:00:52 PM by MiniDave »
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

Offline John Gervais

Re: It happened - zero compression on cylinders 1 & 2
« Reply #11 on: September 20, 2021, 07:15:39 PM »
I've got the MiniSpares competition head studs - I think I used engine assembly lube on the threads, but I'd have to check - it's been years since this head's been off and I honestly can't remember.

I wasn't 'planning' on having the valves replaced, based upon conducting periodic compression tests and it's usually 175ish across the board, but of course, if it's got any warp, it'll get done - precisely why I bought extra valves and bits years ago, just to have 'em 'in case'.
- Pave the Bay -

Offline MiniDave

Re: It happened - zero compression on cylinders 1 & 2
« Reply #12 on: September 20, 2021, 09:05:23 PM »
You can have them skim it slightly without doing a valve job.....or de-carbon it, clean everything up and lap the valves lightly and put it together again....
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

Offline John Gervais

Re: It happened - zero compression on cylinders 1 & 2
« Reply #13 on: September 20, 2021, 09:50:50 PM »
Great idea - I don't know why I didn't consider that; must be tired I guess.   77.gif
- Pave the Bay -