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+--- Thread: Engine Running! Bad Compression & Coolant Leakage :( (/showthread.php?tid=1525)
Engine Running! Bad Compression & Coolant Leakage :( - Eddamoo - 01-08-2018
Hi All!
So last week we got the mighty 750 'Atom' running. Not very well, but the bloody thing ran which we were absolutely elated by. Video here, please excuse the lossy sound compression:
https://www.dropbox.com/s/ztr1yomlxab37sr/VID_20180725_201221.mp4?dl=0
Bad Compression
So talking of compression, fast forward to this week; The father and I were bolting the clutch onto the engine tonight. All was going swimmingly until we started torquing the bolts on the clutch. When moving the engine to get prime wrench access, i noticed a distinct 'hissing' noise when the engine was under compression. As soon as the hissing noise stopped (~3 seconds) the compression was no longer there. Leakage...
We then performed a plugs-out, 12v starter, cold compression test. I know they're supposed to be performed warm, but wanted some indication of a fault. The results in PSI: 65, 65, 65, 70. Damn. We tried adding a spoonful of oil, and the readings came up +5 PSI. I presume a freshly built engine should be in the 90~110PSI region?
The engine was fully re-built around 35 years ago with +040 pistons and has been in storage ever since. I did notice that the cylinder bores were a little glossy but had faith that it would just work. Do you guys think it needs a full overhaul again?
Coolant Leakage
I also tried a simple water loop to ensure the engine was water tight and boy did it fail! Literally all 3 coolant manifold bolts/nut leaked! Is there any magic cure to this short of PTFE tape on the threads?
Many thanks for any input!
RE: Engine Running! Bad Compression & Coolant Leakage :( - "Slack Alice" Simon - 01-08-2018
Engines stored for a long time generally improve with running.
Was it in good nick before being stored?
I would:
Sorry, must have hit the wrong button.....
I would:
check that the head is torqued down to 20 ft-lbs or so
replace the fibre washers on the manifolds with silicon ones to reduce the leaks a bit
probably put a tin of Radweld in
drive it around for a bit, or if not drivable, run it for a bit.
Then have another look.
Simon
Hmmm.
Just looked at the vid - driving is going to be a bit tricky.
Can't hear the engine because of the exhaust noise, but it started ok. Very ok, I think.
Don't panic about water leaks, external ones are usually no great problem.
Having put water in it, though, take the plugs out, bring pistons up and check for water in the cylinders - internal leaks are much more of a worry.
Simon
RE: Engine Running! Bad Compression & Coolant Leakage :( - jansens - 01-08-2018
I am building my engine at the moment. To seal threads I am using this Loctite PTFE stuff that comes on a stick. I think this is the stuff but need to check when I am home: https://www.amazon.com/Loctite-504467-Thread-Sealant-19-gram/dp/B0015PJCHG
I wouldn't use actual PTFE tape in an A7 engine. And bits that break off could easily bung up one of the little oil ways or jets.
I thought it wasn't good to run a new A7 engine without a proper load on it? It's an issue I will have. The engine needs to be running to get the car road legal but I can't run in the engine properly until the car is on the road. Obviously I am a bad Austin 7 owner for only having one and not having another car to swap engines about in
Simon
RE: Engine Running! Bad Compression & Coolant Leakage :( - Eddamoo - 02-08-2018
Thanks again for your advice Simon. The car did run all those years ago, but we're unsure how well.
Yes the car started fantastically - the first time we started it we had a plug out (looking for the elusive spark), yet the thing fired on the first crank with only 3 cylinders! We do have the starter attached to a 12v battery however - is that why its starting so easily?
Ill re-check the head torque after its had a heat-cycle. Then we'll get driving it as soon as possible to see if things bed in.
Jansens - Thanks for the advice. I wouldnt be too worried about running yours. I think the main thing about running in is varying the load and rpm to put varying pressures on the piston rings. This is obviously easier while driving, but cant see it doing much harm doing a bench test.
RE: Engine Running! Bad Compression & Coolant Leakage :( - Hedd Jones - 04-08-2018
It runs nice. No smoke. Id say there was nothing wrong with it.
Sort the water leaks and your away
RE: Engine Running! Bad Compression & Coolant Leakage :( - Robert Leigh - 05-08-2018
(04-08-2018, 04:16 PM)Hedd Jones Wrote: It runs nice. No smoke. Id say there was nothing wrong with it.
Sort the water leaks and your away
Sorry to be late; I've only just looked at this thread. It sounds as though all your water leaks are at the studs on the aluminium water joints. If they are fitted with plain nuts they can be a problem. I always use stainless or brass domed nuts, not cheap but effective. Make sure they do not bottom on the studs, and use new fibre washers. Fibre washers aren't a patch on how they used to be, not squashy enough, but used with a bit of plumbers jointing paste they work fine. The other thing I do if studs need replacing is to use stainless steel, loctited into the block to reduce rusting at that point. Using this method I have had no trace of leakage at these points for 20 years or more.
As for compression, don't worry. It will probably improve with further regular use, and if and when you decide to do something about it there will be other things which have shown up to be dealt with at the same time. If it runs evenly without smoke leave well alone.
Robert Leigh
RE: Engine Running! Bad Compression & Coolant Leakage :( - Ray White - 05-08-2018
I notice your compression readings are all pretty even although a bit low. It is much more important that they are equal rather than how high so don't worry about the reading too much.
RE: Engine Running! Bad Compression & Coolant Leakage :( - Eddamoo - 07-08-2018
(04-08-2018, 04:16 PM)Hedd Jones Wrote: It runs nice. No smoke. Id say there was nothing wrong with it.
Sort the water leaks and your away
Oh it smoked alright! Although i put that down to the fact we had oil in the cylinders for the compression testing. I think we just need to give her a good run, once the wheels and seat are installed!
(05-08-2018, 11:38 AM)Robert Leigh Wrote:(04-08-2018, 04:16 PM)Hedd Jones Wrote: It runs nice. No smoke. Id say there was nothing wrong with it.
Sort the water leaks and your away
Sorry to be late; I've only just looked at this thread. It sounds as though all your water leaks are at the studs on the aluminium water joints. If they are fitted with plain nuts they can be a problem. I always use stainless or brass domed nuts, not cheap but effective. Make sure they do not bottom on the studs, and use new fibre washers. Fibre washers aren't a patch on how they used to be, not squashy enough, but used with a bit of plumbers jointing paste they work fine. The other thing I do if studs need replacing is to use stainless steel, loctited into the block to reduce rusting at that point. Using this method I have had no trace of leakage at these points for 20 years or more.
As for compression, don't worry. It will probably improve with further regular use, and if and when you decide to do something about it there will be other things which have shown up to be dealt with at the same time. If it runs evenly without smoke leave well alone.
Robert Leigh
Thanks Robert, yeah my dad is sourcing some brass/copper washers to see if they help. Thanks for your advice.
(05-08-2018, 01:07 PM)Ray White Wrote: I notice your compression readings are all pretty even although a bit low. It is much more important that they are equal rather than how high so don't worry about the reading too much.
Yeah that's a good thing i suppose! It could always be the compression gauge having an off day (here's hoping!).
RE: Engine Running! Bad Compression & Coolant Leakage :( - Nick Salmon - 07-08-2018
From your posting I am not quite sure where your leaks are coming from but this thread may help.
http://www.austinsevenfriends.co.uk/forum/showthread.php?tid=585
RE: Engine Running! Bad Compression & Coolant Leakage :( - Chris KC - 08-08-2018
Concerning the compression, first thing I'd do is run the test properly i.e. on a warm engine, then you know where you stand. The important thing is whether there is a big variation between cylinders (which there isn't based on what you've shared). An A7 will run pretty well with 65 - 70 PSI so I wouldn't worry too much, as others have said a bit of running-in may well bring about an improvement.