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MG Midget and Sprite Technical - Oh man! HGF!

Just as I thought everything was going well, I think my head gasket has gone.

Car was seemingly running fine, hit a national speed limit sign and gave it some boot, seemed to pull fine. Then as I eased off to cruise it got a lot of put-put-put misfiring and white smoke out of the exhaust.

Crawled home, fortunately only about 10 mins away. Seems ok at higher revs, but chugging and missing at low revs.

White smoke and coolant seemed to be getting pressurised. Gotta be the head, right?

Oh bottoms!

Malc.
Malcolm Le Chevalier

Did it overheat? Is there coolant in the oil or less coolant than when you started?
Jeremy Tickle

Glad you're getting some drive time in! Do a compression test....get your results. If you need a head gasket get a timer clock and see how fast you can do that job! I love doing head gaskets.What ever you do.... don't get frustrated...channel those feelings into conquering the issue at hand! Good luck man!
S

You found a NSL road in Stafordshire?

Wow

As Steven says, knuckle down (with a black Payen gasket, somebody with a memory will remind us of the part number in a minute) and it's not going to be the end of the world

Compression test first then swap gasket and check the oil for crud

Good luck the next time you find a NSFW.... oops I mean NSL road


b
Bill sdgpM

This is probably the one you want:

http://minispares.com/product/classic/TAM1521.aspx

john payne

I had topped up the coolant literally a dribble over the past few days. but I had drained and refilled coolant last weekend for other reasons. assumed it was just working out any bubbles and finding its level. maybe not!

it didn't overheat (that I noticed). I hadn't been going long. I had been struggling with a way lean mix earlier this week after a manifold swap (interesting but long story) so maybe damage was done then.

its no big job to change, I know, but we are moving next week so its bad timing. tho it could have happened on the M6. that would not have been fun!

its a 1500 so that probably isn't the right one ;-) but I will try the appropriate payen for my engine.

Malcolm
Malcolm Le Chevalier

Others have said it Malcolm, but maybe not with enough emphasis. DO get a set of compression readings before you begin to dismantle. Not just to check that it is HGF, but it tells you a lot about engine condition that cannot be as easily checked after you have begun dismantling.
GuyW

Malcolm

I don't think your symptoms are entirely conclusive yet to say HG failure. It does seem likely for sure, but it seems to me your car could still be running unduly hot. It could be your weak mix again, leaky vac hose, crud in the carb etc etc, but personally I would check all that out first.

If symptoms persist, check head nuts are correctly torqued up, and if they are, you may get away with giving them another 1/4 turn. Test accordingly.

Interestingly though, I too had a HG failure after running around with the mix way too lean. It was so bad, the engine was running on, engine bay was hot and I definitely should not have been revving the thing at the time. My own stupid fault....

Classic symptoms are of course loss of cooolant, gas bubbles in the overflow, runs like a dog and overheating, but not necessarily. Sniff test can also verify matters, as can compression test.

Haynes manual tells all if woe is ultimately proved. Yes, also recommend Payen gasket. Clean up both mating faces thoroughly, a smear of blue Hylomar or similar and torque down correctly. Be methodical and take your time. Pretty straightforward... on a 1275 anyways...

M Ogden

well it still did it after cooling down again, and has been ok this week until something deffo broke. checked coolant this morning, down again. really should buy a compression tester one day... :-)
Malcolm Le Chevalier

Well you could try the BK450 on your 1500 but I doubt it will fit! Sorry, I always forget about the 'dark side' of Spridgeting. (Joke!)


Hope you get it sorted.
john payne

Malcolm

I admit HG seems goosed. However, what I was attempting to explain is that is may be futile to fit another if you do not quite understand what caused it to fail in the first place.

For me, as perhaps yourself, it appeared that a lean mix caused the engine to run far too hot for the HG to cope with. Before the new gasket was fitted, I adjusted the mix correctly...HG fine ever since.

M Ogden

Hi Malcolm,


Bad news indeed.


I had asimilar experience on a rebuilt engine a cpl of years ago, the Hg failed in about 900 miles.


I put it down to a poor quality gasket, replaced with a Payen one, with new head studs and uprated nuts, plus torqued up an extra 5ft/lbs been fine ever since.



Regards Steve.



SR Smith 1

I seem to recall the 1500s had 2 differant sytyles of hg... but interchangeable


I dont agree with the add 5 ft lbs of torque... you can easily over crush the fireing ring


prop
Prop and the Blackhole Midget

Not really bothered if you agree or not Prop tbh!


All I can say is its now down 2,200 miles since being changed with no problem at all.
SR Smith 1

The theory is that if you overtighten the head nuts the fire rings crush and the clamping pressure is spread over the whole surface of the head gasket, rather than just on the narrow fire rings. As such the pressure (force/unit area) is actually reduced, not increased, on the part of the gasket designed to take the combustion pressures, if you over tighten.

Maybe it has worked for you for a couple of thousand miles, and maybe it will last a lot longer. But its not the recommended method. And its not just one of Prop's bright theories!

<<over-torquing will almost certainly distort the gasket to the point where failure is likely to occur. The most likely areas are the fire-rings that seal the head face>> Keith Calver
Read about it here: http://tinyurl.com/hlo3va3
GuyW

Just caught up. Tough luck Malcolm, you have my deepest sympathies.

After two failures I sourced a Payen from Rimmers. I gave them my engine number at the parts desk and hey presto its been fine since.

As far as I know I did the same things each time.

I user the original bolts except one that was rusty, two would not come out of the block as they were rusted in and I used the original hardened washers and nuts as the Rimmer ones looked suspect. I am sure Guy is correct about overtightening so made sure all threads were clean and lubed with 20/50. Its all I had to hand at the time that I knew was OK at engine temperatures.

If anything was different by the final time apart from the gasket it was the head and block faces were super clean and the threads were super slidy. I retightened hot on return after my first run around the block. (7 miles)

Remember I never did anything like this before and its worked fine for two years and still a OK. If I can get it right then I am sure you can.

Good luck. Dave
Dave Squire

I may be opening up a can of worms here, but I thought standard bolts should be torqued dry.

That's what I did after an HGF a couple of years ago that was sorted with a Payen gasket.
Peter Blockley

Guy

In a perfect world you would be correct, but very often mating surfaces are not as one would wish, the gasket has a tolerance, the head could well be warped - albeit invisible to the naked eye - the torque wrench has a tolerance etc etc.....

Increasing the torque slightly, or nipping up by 1/4 turn may not actually over-torque the gasket or do any damage to it - despite what the torque wrench says.
M Ogden

Good point that.

How many, hand on heart,can say the torque wrench in their garage is 100% accurate?
SR Smith 1

100% heart clutch 6 months ago

http://advrider.com/index.php?threads/harbor-freight-torque-wrench-torque-adapter-testing.860246/
Prop and the Blackhole Midget

Steve,

That rather changes the argument! On the one hand to recommend adding 5 ft lbs to the manufacturer's specification. And then saying that one shouldn't rely too much on the accuracy of a torque wrench that has not been recently tested or re-calibrated. By that argument the wrench could already be reading low, or high, or spot-on. So you are suggesting adding 5ft lbs to what exactly?

My comment on over torquing wasn't my invention. Or Prop's. Which is why I posted the link to Keith Calver's article. I don't seek to change your advice, but to provide the explanation for the argument in favour of using the specified figures, I thought it an interesting read.

And Peter's comment about torquing dry accords exactly with Calver's advice in that article. I understand (though sorry, I cannot at the moment quote a reference for this) that oiling the threads can result in over-torquing by anything up to 40%
GuyW

True Guy,

Should have said at the time, but I used a state of the art Snap-On elecrtonic one recently returned from overhaul when I did mine last, so can be reasonably sure it was about right.



Being in the trade I have access to good quality tools.
SR Smith 1

Fair comment in your case at least you do know your starting point then Steve. ;-)

So back to not inaccuracy of torque wrenches but whether it is good practice to add a bit to the manufacturer's spec. Maybe it is, but Calver's article explains why he thinks not.
GuyW

Bill, no need for NSL roads in Staffs as there are so many pot holes the roads are self regulating.
Peter Ottewell

Really good link Prop. Thanks.
I didn't know that the bendy-beam type were more accurate, but they are inconvenient IMO.

It's reasonable easy to check for yourself with care. When I do it I check it at the torque setting I'm about to use. I use an old 25 litre oil can that I weigh accurately then add an accurately measured quantity of water, plus whatever other weights are needed. That doesn't calibrate the wrench properly, but it tells where to set it for the click and the test is easily repeatable.

My current wrench checked out spot on at 90 and 120 lb/ft last week. FWIW I've never found it more than 2 lb out. BTW I was taught always to back off the spring load completely before storing it. Some people don't.

My fave that was stolen a couple of years ago was my grandfather's. It had a calibration stamp from 1936 and when I had it checked in 2010 it was perfect. They don't make them like that anymore!

As to lubricating the bolts - my understanding is they should be super-clean and the threads in perfect condition, but dry, except for specials like ARP bolts that spec their own lubricant and torque settings. As always I'm happy to be shown to be wrong; that's how I learn.
Greybeard

Wow! This has taken off this evening.

Head off and gasket replaced with Payen today. It was defiantly knackered. Can't really be sure of the root cause as I have been messing about with all sorts of things of late. I thought I was on top of things when it blew, but the damage was already done.

I also found another issue which I am not sure if I want to share! It is embarrassing and amazing in equal measure, its correction should defiantly help with the tuning in the future.

Not been able to get finished up today as I couldn't find my feeler gauges to set the valve clearance (I have loads of stuff in storage at the moment). Moving house tomorrow so won't be able to get finished until the weekend at the earliest.

Thanks everyone.

Malcolm
Malcolm Le Chevalier

As for NSL, the A513 between Milford to Wolsely Bridge. It's only 10 mins, but a fun bit of road. It's on the route between my parents house and their work so have driven it a few times.

Going from W. Bridge to Milford, there is a NSL immediately after a small roundabout. Good for a 20 - 60 mph blast. At the Milford end it is pretty up and downy with some fun bends.

Malcolm
Malcolm Le Chevalier

Ha! How do you know you are weighing your 25l oil can accurately?

Actually, what I really wanted to ask is, what are you torquing to 90 and 120 lb/ft?
Nick and Cherry Scoop

Nick...

Certified digital scale to weigh the can, which I only needed to do once as I wrote the weight on it. Actually I need to find another as the old one is starting to break up where the rope goes through.

90/120 lb/ft was for head bolts on a marine diesel. They had to be turned another 90 degrees from there!
Greybeard

You must have a splendid workshop, Greybeard.
I think if I suspended a hundredweight or more, a foot from the edge of my bench, it would pull out the screws holding it to the garage wall.

I fill a plastic bag with groceries, on the bathroom scales. But only up to 45lbs.
Nick and Cherry Scoop

My Teng Tools torque wrench has been sent away for recalibration "by e manufacturer" twice now. I am not exactly sure where it actually goes to, but almost certainly not to where it was made! I take it to the tool shop that supplied and they send it away. It comes back all cleaned and oiled, date stamped and with a calibration certificate. The first time it was free of charge. The second one cost me £10.
GuyW

My comment ref torquing up the head was to take into account of all tolerances and deviations from the norm which may adversely affect the specified torque setting - in so far as the specified torque setting for the head may be a touch inadequate if these are all taken into account. In other words, I believe torque settings are factory recommendations, and if the elements concerned are not sufficiently close to factory conditions, one may need to take account of that.

However something like wheel nuts - for example - and indeed most other places where a torque setting is specified, similar factors, if indeed any exist, would not present sufficient concern to deviate from the specified torque setting. Here, I would agree that abiding by the recommended torque setting is certainly a wise thing to do.

M Ogden

I bought one of those digital torque meters, super bit of kit for use or checking for the price, it also has an angle setting function.

with left hand threads I think you need to make sure like a torque wrench it can can measure clock and anti clock directions.


I managed to rip a bench off its base trying to remove a clutch post fastened in a vice, so it can be done !
mog

Yep Nick - it's a good shed, if a bit cold in winter. It's 6x10 metres. The benches are in an "L" configuration into the corner. 16 feet in one direction and a bit over 10 feet the other.

I built them from pretty chunky timber. The frame and legs are 4x2 CLS and the tops are 3 lengths of 10x2, with MDF on top for a flat surface, which is intended to be sacrificial.

I'm not sure my vice would be up to the strain, so I borrowed a tool a mate made which is a piece of heavy steel angle section roughly 18" long with an old socket welded onto it. That can be clamped down where required.
Greybeard

I bought one of these digital scales for my e-baying activities a year or so ago. I found that using it to pull the torque wrench handle at various torque settings confirmed my wrench was still pretty well calibrated.

http://www.ebay.co.uk/itm/191161510810

Jim
J Smith

It doesn't look strong enough to carry 40kg, does it? And less than three quid!

Nice bench, by the way. Mine is 1.2m x 0.7m.
Nick and Cherry Scoop

>>It doesn't look strong enough to carry 40kg, does it?

You wouldn't think so, I must admit I've not tried mine above about 65 lbs and it seemed fine. This is what its like inside. (Sorry for going OT!)



J Smith

Any pictures of the old head gasket Malc? Did you find an obvious flaw? Sometimes its hard to pinpoint the culprit offending area. Hope you have a safe move and you get the car up to snuff soon.:-)
S

Nice picture, Jim. But, where's the measuring bit?
Nick and Cherry Scoop

There is a strain gauge stuck (with white epoxy?) to the metal strip which measures the slight bending of the strip. Clever in that there are no 'moving' parts as such.....

J Smith

Here you go Steve, if you are still reading!



Malcolm Le Chevalier

Hmmm Didn't look destroyed. I wonder if you had retorqued if it would have helped.

No worries...you've already done the job...I would have done just what you did!
S

I wondered that too, after dismantling. the head nuts seemed a little variable in tightness. also, when I took all the studs out in order to clean the block better, I managed to get all the right hand studs out by hand. but the left hand studs needed more force (two nuts method). struck me as odd.

the whole re torque thing seems to be a minefield.

Malcolm
Malcolm Le Chevalier

This thread was discussed between 19/03/2016 and 31/03/2016

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