MGA breathing heavily
Discussion
I asked the following question in the classics section and was pointed overvher:
Hoping someone can help here - we've got an MGA with a motor that's been freshly rebuilt. It seems to run well but is losing a fair amount of oil out of the breather. Also seems to be heading toward overheating when run round town but no issue when out of town.
Many thanks in advance!
Hoping someone can help here - we've got an MGA with a motor that's been freshly rebuilt. It seems to run well but is losing a fair amount of oil out of the breather. Also seems to be heading toward overheating when run round town but no issue when out of town.
Many thanks in advance!
Assigning oil burning issues is not easy. As the engine has just been rebuilt that points the way to an issue with build.
Do any plugs foul up? If you use a torch can you see oil sat on top of any pistons? You mention oil coming from breather so that points towards ring sealing problems which can be caused by rings or bore finish/size or both. If the breather is the standard MGA venting to atmosphere rather than being drawn into air filters or carb bodies it does point to piston/bore problems.
With regard to overheating, MGAs can be naughty for this, even the angle of aftermarket grille slats can lead to overheating. We have come across quite a few examples of waterless coolant leading to overheating which goes away once it is replaced with water/antifreeze mix. Poor radiator condition can also lead to overheating. Retarded ignition timing allows the engine to run warmer adding to the inherent MGA woes but you do not mention poor performance.
Peter
Do any plugs foul up? If you use a torch can you see oil sat on top of any pistons? You mention oil coming from breather so that points towards ring sealing problems which can be caused by rings or bore finish/size or both. If the breather is the standard MGA venting to atmosphere rather than being drawn into air filters or carb bodies it does point to piston/bore problems.
With regard to overheating, MGAs can be naughty for this, even the angle of aftermarket grille slats can lead to overheating. We have come across quite a few examples of waterless coolant leading to overheating which goes away once it is replaced with water/antifreeze mix. Poor radiator condition can also lead to overheating. Retarded ignition timing allows the engine to run warmer adding to the inherent MGA woes but you do not mention poor performance.
Peter
832ark said:
I asked the following question in the classics section and was pointed overvher:
Hoping someone can help here - we've got an MGA with a motor that's been freshly rebuilt. It seems to run well but is losing a fair amount of oil out of the breather. Also seems to be heading toward overheating when run round town but no issue when out of town.
Many thanks in advance!
Explain "rebuilt", as it can mean many things.Hoping someone can help here - we've got an MGA with a motor that's been freshly rebuilt. It seems to run well but is losing a fair amount of oil out of the breather. Also seems to be heading toward overheating when run round town but no issue when out of town.
Many thanks in advance!
And did it ever have any similar issues before being "rebuilt" ?
Thanks both, only issues pre rebuild were a bottom end knock as as result of wear. Turned out the bottom end had never been apart. It had the crank ground, new pistons, reciprocating mass lightened and balanced, rebored block, all new bearings throughout, new camshaft, new rocker assembly, new oil pump, new water pump, head refurbed etc.
Haven't done any further investigation yet but mainly wondering how heavily these engines should breath when freshly built?
Haven't done any further investigation yet but mainly wondering how heavily these engines should breath when freshly built?
832ark said:
Thanks both, only issues pre rebuild were a bottom end knock as as result of wear. Turned out the bottom end had never been apart. It had the crank ground, new pistons, reciprocating mass lightened and balanced, rebored block, all new bearings throughout, new camshaft, new rocker assembly, new oil pump, new water pump, head refurbed etc.
Haven't done any further investigation yet but mainly wondering how heavily these engines should breath when freshly built?
No engine should breathe heavily.Haven't done any further investigation yet but mainly wondering how heavily these engines should breath when freshly built?
Who rebuilt it ? correct piston/rings used ?
Also was the correct oil used, i.e. not a synthetic?Freshly built engines should not breath, but, I suppose, you need to quantify and qualify what 'breathing' means to you?
To try and help you I need you to answer the questions I posed to you in my first reply to you. There are quite a few variations in breather set ups so it would be helpful to know what type you have. Even the make of piston used for rebuild can give a little clue. I forgot to ask, is it still a three bearing engine and what capacity?
What does the engine builder say to you?
Peter
To try and help you I need you to answer the questions I posed to you in my first reply to you. There are quite a few variations in breather set ups so it would be helpful to know what type you have. Even the make of piston used for rebuild can give a little clue. I forgot to ask, is it still a three bearing engine and what capacity?
What does the engine builder say to you?
Peter
Gloopy oil whatever it is made of seems best. We used to use Pro4 but for quite a few years it hasn't been the same concoction. We like Valvolene VR1 in the race engines. Classic Castrol seems ok etc etc, as you say Stevie, a bit of a red herring, the engines do not seem to thrive on water thin oils with large diameter oil ways. As with any engine running in oil should be used, preferably straight grade with no additives in. Arrested running in problems when asperities are merely 'bent' over and not bedded in have only shown up as using oil not breathing from our perspective.
Peter
Peter
stevieturbo said:
Not sure it's as big a deal as some make out, but in an old engine like that, prob using mineral oil anyway ?
I personally think it makes a huge difference when running in engines, most particularly older ones. My grandfather used to run a Lamborghini tractor dealership and there were real problems with engines breathing heavily and using lots of oil from new. Lamborghini issued an instruction to drain the synthetic oil they were filled with at a factory on new tractors with and run in on mineral oil which fixed the problem.Whether this was down to a material problem or honing pattern I don't know, but I've always run in rebuilt older engines on mineral or semi-syth since then.
I agree it should be running on a mineral oil anyway, but doesn't hurt to ask.
Edited by Mr2Mike on Sunday 5th March 13:50
Thanks guys, I got to take a look at it this evening and I think I've found the issue, let me run this past you:
Standard breather system for those of you that don't know is like an upside down hockey stick which vents via a 90 degree elbow from a hole in the tappet chest cover. The high point of the curve is above the hole in cover - I assume this is to stop liquid oil from escaping out of the breather. What has happened is that the elbow has popped out of the hole and oil is then free to escape directly from the hole. Not sure how much oil there is generally splashing around the tappet chest area? So possibly it's not breathing heavily at all and is just leaking oil. Unfortunately I can't get the elbow back in position so will have to remove the manifolds and make sure it's very well seated this time.
As for the overheating, it was definitely low on water so maybe there was an air lock or we have a leak - will have to investigate further on a dry day.
Peter - you're clearly an expert on these engines having checked out your website. Not to far away either as we are in Stafford. Car runs pretty well but obviously needs setting up properly - assuming of course we get the breather and cooling issue sorted what sort of mileage would you say is sensible to get it properly tuned? Not looking to extract the maximum possible power, just a smooth running, easy starting nicely idling motor.
Standard breather system for those of you that don't know is like an upside down hockey stick which vents via a 90 degree elbow from a hole in the tappet chest cover. The high point of the curve is above the hole in cover - I assume this is to stop liquid oil from escaping out of the breather. What has happened is that the elbow has popped out of the hole and oil is then free to escape directly from the hole. Not sure how much oil there is generally splashing around the tappet chest area? So possibly it's not breathing heavily at all and is just leaking oil. Unfortunately I can't get the elbow back in position so will have to remove the manifolds and make sure it's very well seated this time.
As for the overheating, it was definitely low on water so maybe there was an air lock or we have a leak - will have to investigate further on a dry day.
Peter - you're clearly an expert on these engines having checked out your website. Not to far away either as we are in Stafford. Car runs pretty well but obviously needs setting up properly - assuming of course we get the breather and cooling issue sorted what sort of mileage would you say is sensible to get it properly tuned? Not looking to extract the maximum possible power, just a smooth running, easy starting nicely idling motor.
We have our own recommendations for running times before rolling roading when we build engines. To be honest, out of respect for your engine builder, you should really ask them for their recommendations for running in before rolling roading.
Better sort the overheating as that is not good especially for a new engine.
Peter
Better sort the overheating as that is not good especially for a new engine.
Peter
Thanks Peter, will see what they recommend. They suggested a 500 mile break in period. Fortunately it didn't actually overheat but started to climb and so was shut down and allowed to cool (I wasn't with the car at the time and only had chance to take a look at it this evening.
Does my hypothesis on the breather sound sensible?
Does my hypothesis on the breather sound sensible?
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