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MG Midget and Sprite Technical Yup, head gasket! BBS discussion at MG-Cars.info
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MG Midget and Sprite Technical - Yup, head gasket!
| For those following the other thread, this is a continuation from that... Disassembled things tonight, it didn't really take that long, I was in the garage about 2 1/2 hours and stripped the rad out, timing cover off (to sort an oil leak) and head off and cleaned them all up ready for reassembly. The head gasket was totally junked. It had a leak from the water way into 2 and 3 and burnt through 1 and 2. The gasket itself wasn't stuck to the head at all and peeled off the block with zero stickiness/effort (if that means anything?). For such an epic gasket fail after < 5 mins I suspect I have made a bit of a cock up somewhere along the line, so I will be super extra tidy and meticulous on reassembly tomorrow with a new gasket and new studs for good measure. Pictures to follow once I get them off my new fangled telephonic calling contraption! Cheers, Malcolm |
| M Le Chevalier |
| Hi Malcom. If it makes you feel any better, I once had a new head gasket blow after driving just 200 yds. And the reason? - in fitting the head (1500) I had managed to trap the thin vacuum advance tube as I lowered the head down onto the block. It was just caught at the rear of the block, but that was more than enough to stop the HG from sealing properly! |
| Guy Weller |
| Is this on a 1275? If so, check to be sure none of the water passage plugs have recessed into the head. |
| Trevor Jessie |
| It is a 1500 Trevor. Pic one, block. A bit blurry. 
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| M Le Chevalier |
| Pic 2, head. Cylinder 1 to the left. Number 4 the only one that did seal! :-D 
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| M Le Chevalier |
| The other thing to watch for on a 1500, is that you use the correct gasket with the extra thickened fire rings to match the grooved recess around the cylinders in the head. It shouldn't be a problem with the right gasket set, but IIRC there can be an issue if you use a generic Triumph 1350/1500 gasket. |
| Guy Weller |
| Oh that ain't fun Malcolm. The first thing I wondered about. Is your torque wrench up to the job? The entire face is so clean it makes me wonder why. Are the stud threads bottoming below the head face or is there a portion of unthreaded stud that the nuts are bottoming on instead? Hope you get sorted ASAP, summer won't hang around. |
| bill l |
| using NM instead of lbs ft? NM 36% lower than lbs ft. Or wrong gasket as Guy says or both? Peter |
| Peter Burgess Tuning |
| Flash backs, deju vue, my head is spinning... I seem to recall this nightmare. Wheres viet charely, wheres viet charley....ohhh the colors dude, the colors I can smell the exhaust ... it smells like victory, rambo style Its like a french version of ptsd Prop |
| Prop and the Blackhole Midget |
| Hi Malcolm, Get a Payen or better. After two failed attempts with standard gaskets a Payen fixed mine 8000 miles ago. One can be had for about £20 :-) |
| Dave Squire |
| Check you have all the studs the right way up. The shorter threaded ends go into the block. Get them the wrong way up and as Bill says, the nuts will reach the end of the threaded bit before clamping the head down fully. |
| Guy Weller |
| Don't 1500 head studs have a different thread at each end like A series then? |
| graeme jackson |
| Just to answer a few of the above comments/questions. - Yes studs were right way up (same thread each end, but shorter end in the block). - Yes, torqued in Nm. The wrench doesn't read in ft-lb and if I don't think I could set it using the ft-lb measurement as it would be off the bottom of the scale. - Torque wrench... dunno. I have had it two or three years, it doesn't get used a great deal, but it has been used a few times right at the top of it's range (200 Nm). - Gasket was correct and on the right way. I did change the standard nuts/washers for "uprated" flanged nuts, although I don't see what difference this would make. I still think I have just messed up something basic on the rebuild like the torquing sequence or something, maybe I missed one nut by accident on the final 63 Nm round. Hopefully new gasket will arrive today and I can rebuild tonight :-) Cheers, Malcolm |
| M Le Chevalier |
| Just check the flanged nuts didn't run out of thread? Peter |
| Peter Burgess Tuning |
| Yup, plan to check that tonight. Should I put a washer underneath if they do? Seems to defy the point of the flanged nut. Also, is there an easy way to check this? Malcolm |
| M Le Chevalier |
| If you do a flat washer ... use only flat and grade 8 Im not sure where your getting your NM torque spec from... but make sure the NM spec is properly converted from foot pounds and NOT inch pounds In the usa we use both specs of foot pounds (ftlbs) and inch pounds (inlbs) tho inch pounds are more common for lawnmower type of engines Id say there is a good chance you oil leak was from the head if it was that loose Check your head for flatness with a (tru) straight edge... not just a 99 cent childs ruler Im not sure about the 1500 but on the 1275, the studs are only finger tightened into the block... no tools used id think the same applies to the 1500, over tightening head studs in the block can screw up the final torque setting Id also try a thin coat (THIN) of copper seal, it makes a better seal and fills in minor scratches....spray only the Head Gasket and not the deck or head surfaces Im a big beliver in hot retorqing...after its ran good and hot the 1st time shut it off and immediately retorque the head agian...I didnt back the nuts off, just set the torque wrench to its final setting and applied a slow non jerky positive force to the nuts in the proper pattern Prop Prop |
| Prop and the Blackhole Midget |
| Malcolm, After the final torque to all studs, I always start over again with the final torque setting to make sure that the ones done earlier in the sequence did not get altered by having the rest of them torqued more. I keep going till nothing moves. Also, if time and patience allows, let it sit over night and then check it again. If you have access to a second torque wrench, link them together with the correct socket and pull them against each other to see if they agree. Of course they could both be off, but for both to be off by the same amount seems unlikely. To see if you are running out of threads, measure the thickness of the head and measure the unthreaded portion of the stud above the block. Compare the two to see that you have enough margin. I don't know what margin you should have, but I think you would want at least as much margin as the gasket is thick. Charley |
| C R Huff |
| Visual check should suffice, no harm in fitting the washers too. Peter |
| Peter Burgess Tuning |
| >>>>Visual check should suffice, no harm in fitting the washers too.<<<< I hope im not alone in respectfully asking.... hmmmm ???? Does that involve the X-ray glasses prize in the crackerjack box *¿* Or I the only one that cant see visual torque in the room. :-) Prop |
| Prop and the Blackhole Midget |
| Studs are fine. Fitted a couple, then fitted the head without the gasket (with masking tape to protect the surfaces). Threads were still below the level of the top of the head. It took a couple of turns of undoing before the shank of the stud showed, so plenty spare. Head is as flat as a snooker table. Bought a new torque wrench, just waiting on gasket. Tried to refit timing cover, one of the threads at the bottom stripped (not the one into alu, PO already helicoiled them to a UNC thread). Had to helicoil, so now need to remove sump to clean out the swarf. Probably a good thing as sump gasket is a bit leaky I think. I think the picture sums it up! Malcolm 
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| M Le Chevalier |
| Prop, I think Peter meant visually check if there is enough thread on the studs. But, I haven't really answered your question, have I? Yes, I'm pretty sure you are the only one who can't see visual torque. It helps to take off your glasses and squint your eyes a bit. Also, it's more visible on a new moon. Try a little harder and I'm sure you will get the hang of it. Charley |
| C R Huff |
| Hahaha.... So that was my head and gasket problem all along!!!!.... I cant see visual torque ... hahaha Yeah I wasnt sure wear peter was going with that comment...makes scence Something to consider, when you torque that head down you can easily loose 3/8 inch of your cly head height, from squishing it down so id say you want an extra 1/2 inch of threads then when the head is just sitting into a static place and no torque is applied Prop |
| Prop and the Blackhole Midget |
| Prop, what is your head made from? |
| Dave O'Neill 2 |
| which one? |
| Nigel Atkins |
| Cast iron, but the smaller head never rises to the occasion anymore so 3/8ths proud is fine :-[ Prop |
| Prop and the Blackhole Midget |
| Old MGs never die.....They just go faster! :-) |
| Steven Devine |
| The worst I ever saw Prop, was a customer who timed his TR6 cam in by feeling the high point on the cam with his thumb, usually I expect people to answer, when I say did you time the cam in?....half past two or 'two thirty' to dental patients :) Peter |
| Peter Burgess Tuning |
| Seeing torque is easy. Hearing it is the skill... "uff" = 20 Nm "urgh" = 50 Nm "huurgh" = 70 Nm "hurrraaaaghh" = 100 Nm x number of hurrraaaaghs. "eeeeeeeeaaaafffeck" = 2% more torque than is required to strip the threads. Shout out to Moss btw, I know a lot of people slag them off, but they always have absolutely everything in stock and I just got a Payen gasket for the price of a regular gasket (£13 vs £20). Cheers, Malcolm |
| M Le Chevalier |
| Peter What did you say to the guy, id like to have been there to actually see that...an idiot timming his cam in with his thumb print... You never really see it all do you.. theres always one more idiot just anxious to prove you aint seen it all just.yet Prop |
| Prop and the Blackhole Midget |
| Oh yes! |
| Dave O'Neill 2 |
| New payen gasket on. With new studs and the "uprated" flanged nuts. Head and block cleaned, cleaned again and cleaned a third time, yesterday and today!! Clicked off all the nuts nicely in order at 25nm, 45nm then the full 63nm. The round again at 63nm just to check. All with spanking new wrench. If this one goes I am retiring! Next leak to fix appears to be a rear cylinder. I can't fix all the damn leaks on this thing fast enough before something else starts leaking!! Cheers, Malcolm |
| M Le Chevalier |
This thread was discussed between 14/07/2014 and 16/07/2014
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