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MG TD TF 1500 Problem- new findings BBS discussion at MG-Cars.net
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MG TD TF 1500 - Problem- new findings
| Having removed the head on my TF with the oil burning problem I have found the following. The valve seals are OK and pass the 'oil on the keepers' test, however on replacing the head, and fitting new seals, it still blows smoke. There seems to be a copious amount of oil going through the rocker gear. I have restricted the flow to the head by soldering up the oil hole in the banjo bolt and re-drilling a 3/64 hole. Has anyone had a similar problem, should I restrict the oil flow further? I have run the motor without the rocker cover on with plenty of towels to cover the oil getting chucked about, but it still seems excessive. The compression is good, new guides, in fact the engine has done only about 10 miles.
Regards, Don TF 4887 |
| Donald J Walker |
| Don Did some googling and found--- Factory manual quote:" Commencing at Engine No.31943, the lower banjo coupling on the oil pipe (gallery to head) has had the internal diameter reduced to .055in. (1.39mm) Your 3/64" equals 1.19mm----I think I'd be a bit worried about going much smaller Maybe a phonecall to Bob Schappel might be an idea - He would know where the limit is |
| William Revit |
| I assume the smoke is blueish burnt oil smoke, not water vapour. If so, as it is only seen on the over-run, then oil is being sucked in either past the piston rings or down the valve guides. Your description implies that you only have the original O rings that fit under the cotters - although I am slightly puzzled by your 'replacing the head and fitting new seals' - do you mean 'after' fitting new seals. Anyway, have you tried fitting valve stem oil seals on the four inlet valve guides. If you do, you must cut down, but not remove, the spring inner shrouds.
Do not fit stem seals to exhaust valve guides - there is no suction from the inside, only pressure and heat. Thus the exhaust guides often run rather dry, so the occasional drop of oil down them is of benefit, and it soon gets burnt and pressured back into the rocker cover chamber. I would suggest, initially, not cutting down the exhaust valve spring shrouds (although I did in my XPAG engine with no adverse results). You say the compression is good, but do you have the exact figures. This is because it is possible to break a piston ring during assembly, and one broken ring might only give a small reduction in compression pressure. Have you checked if one spark plug is oilier than the others, or when you had the head off, was one piston top darker (burnt oil) than the others. Regarding the oil hole in the banjo bolt - I have reduced it to 1mm, making sure any burrs were removed from both sides. My TD rockers are the same as your TF rockers, and the wear is negligible after thousands of miles. However, I don't think the hole size is your problem. |
| R A WILSON |
| Don, If it blow smoke all the time .... Did you check that the valve Oil Deflector shroud was installed the right way round ? If it is installed under the valve springs (at the bottom) It will pool oil around the valve guide and smoke all the time. Even though the O rings are doing there job correctly. Seen it once before in Germany on a TC after an engine shop had installed them upside down. Easy fix. Rod  |
| Rod Jones |
| Ideas : If you have sleeves in your rebuilt engine. Are they level with the block or slighly above ? I had similar issues due to small end gaps for piston rings. Before dismantling, ask the rebuilder for the end gap he trimmed. Laurent. |
| LC Laurent31 |
| It might also be useful to know if you have 3 or 4 ring pistons, and if the bottom oil control rings are one piece cast rings, or the much better three piece spring loaded twin blade rings. |
| R A WILSON |
| Some interesting scenarios here.
Willy, I will check the diameter of the lower oil hole today, and yes, we do have a bridge over to the island. Must have been many years since you were over here. RA, when I removed the head I replaced the seals with new ones....hoping! The rings are the 3 ring with 4 segment oil rings, if necessary I will remove the pistons to check these. Rod, the oil deflectors are in the correct position. Laurent, the block was bored out to .060. I will do the Basil Faulty thing and take a large branch out to it today and threaten it!! Don TF 4887 |
| Donald J Walker |
Do you know if extra seals, as in the attachment, are fitted at the top of the inlet valve guides - they would be inside the springs.
 |
| R A WILSON |
Do you know if the bottom piston rings, the oil control rings, are the type shown in the attachment
 |
| R A WILSON |
| RA, no extra seals and yes to the oil control rings, but they do have one extra segment, they are Hastings brand. Regards, Don |
| Donald J Walker |
| RA, these are the rings, I presume the extra one is an expander ring. Don  |
| Donald J Walker |
| The problem may the 10 miles. I would drive it long and hard, at least a couple hundred miles to seat the rings before doing anything else. I think Tom Lange made some comments about some brands/types of rings being hard to get bedded in? George |
| George Butz |
| Taking the rings first, my illustration is obviously from another manufacturer, but as a general design they are probably the best available.
Regarding the seals, you should consider fitting them - many T, Y and W owners end up fitting them. They are sold by Moss, part number ADU4905. I am not sure of the exact design sold by Moss, as some are simply pushed onto the ends of the valve guides (a touch of superglue might help), and some need a groove a short distance down the valve guide. If the second design, the inlet valve guides must be removed to have the required groove cut using a lathe (I suppose you could use a small round file). Moss say the spring inner shrouds should be removed, but it is better to cut them down, as MG suggest in their Special Tuning. I accept the exact reason for the smoke from your engine has not been established, but fitting the above seals is a good next step, even if it means removing and stripping the head. I still think knowing the exact compressions would help, and if any spark plugs are dirtier, with oil, than the others. |
| R A WILSON |
| RA, I reduced the bottom banjo oil feed hole from 5mm to 2 mm, this had a marked improvement on the blowing of smoke....until the excessive oil problem in the rocker area came to light. The stem seals you mention that don't require machining...do you have a number for them? Maybe I've done something silly but I can't think what. I will re-do a compression test including a wet one. Or I may push it quietly into a corner on work on the SA Tickford. Thanks for all the suggestions and ideas. Regards, Don |
| Donald J Walker |
| Don, there is supposed to be copious oil in the rocker area on these engines. It helps cooling the valves as and more importantly drips/runs down to lube the cam. If your valve stem to guide clearance is correct and all is assembled correctly that is not the problem. Restricting oil flow will reduce camshaft/lifter lube and you will end up with a ruined cam and lifers. The rings not bedding in is a known problem in the US. Again, suggest talking to Tom. George |
| George Butz |
| Don and George - yes, I have had problems with Hastings rings not sealing, even after a few thousand miles. The engines smoked and smoked and smoked from the first stqart-up, and nothing made any difference. I broke in the engines as I always do - I drive for about a thousand miles accelerating through the gears, then backing off to allow vacuum to suck oil up into the bores - up and down, up and down; not keeping the engine at the same RPMs for long usually works. Upon disassembly I found that there was no sign that the rings had seated in the bores.
I switched to Deves rings, and have had no problems at all - they smoke on start-up also, but seat nicely in the first 1000 miles. Your limited mileage is not enough to get a seal with ANY rings, so I would just contimue to drive it, following your favorite break-in regimen. If it still smokes after a thousand miles, then start pulling it apart. Tom Lange MGT Repair |
| t lange |
| Not sure about reducing the bottom banjo to 2mm - I didn't alter mine.
Looking at the Moss seals on their website, they do not say that grooves are required, and I now remember that I fitted Moss seals, and I did not machine grooves. Although the Moss illustration seems to show an inner bead at the leading edge, I think it is just to get a good tight fit. As I mentioned, superglue on the guide, so that the seal pushes into it, might help, although I cannot remember if I used superglue. Assuming the above, it might be possible to fit the seals without removing the head by holding the inlet valves up one by one from within the combustion chambers. As I understand, the springs are then removed using a lever system on the rocker shaft or bolted to the head, but I have not done this myself. I do agree with George and Tom - it should be worth putting in some more miles (take a gallon can of oil), and then checking for smoke. |
| R A WILSON |
| Expanding on RA Wilson's mention of changing the seals in place here is a video describing the process. https://www.youtube.com/watch?v=_uO5YayiLrA I use a slightly different approach to that shown in the video. I break out the ceramic insulator from a spark plug and braze on an air fitting. Then use the hollowed out sparkplug with the air fitting to pressure the cylinder. I find that easier than stuffing rope in the cylinder. Tim TD26711 |
| Tim Burchfield |
| I concur with George and Tom's assessment of your rings not being bedded in yet due to lack of mileage.
I remember when I first got my TC running after restoration, it smoked like a chimney out the exhaust. I went to GOF South while it was smoking and had John Twist try and diagnose it at the tech session. The only thing he could come up with was lack of mileage, most everyone else concurred. I was popular though because it kept down the mosquitoes. They were right...after a couple of hundred miles of bedding in the engine stopped smoking. Give it time. Gene Gillam Saucier, MS |
| Gene Gillam |
| I had the same issue with my 53TD the last time the engine was rebuilt. It smoked at idle for several years until I had enough mileage on it and then the smoke was gone. It took so long since I only put 100 or so miles a year on it. Jim |
| James Neel |
| Don
Did the Basil branch work, sometimes they just need a good talking to A BRIDGE to the island That's special Cheers willy Years ago we were lucky/unlucky enough to get marooned on the Aroona when she ran aground out at the mouth and had to get ferried over to the island by a local dingy fisherman and made our way back to the barge to Goulwa It was quite an eventful day, Our boys were only little tackers then and it made a huge impression on them, Something they will never forget-----Fantastic experience for them |
| William Revit |
| Don Just a thought- What oil have you got in there |
| William Revit |
| Well the general consensus is to put more miles on it which I will do. I have built XPAG motors previously and never had any trouble with smoke from go. I value all the experiences here and feel better about the outcome. I have heard of Deves rings and may try them next time. Hindmarsh Island here we come, but not if there is a bushfire warning! Willy, I don't if you did it on purpose but it's Goolwa. Regards, Don |
| Donald J Walker |
| When you first posted your problem, the question was raised a couple of times what the plugs look like. That is the first examination to perform when an engie burns oil or runs rich. I don't recall ever reading the answer. Is there one, two, all four plugs or zero plugs blackened or wet? |
| JIM N |
| JIM, all plugs are black but the smoke has reduced quite a bit, I will go with the drive it more theory and see how it goes. Don TF 4887 |
| Donald J Walker |
| Sorry Don Goolwa it is My question on oil was leading towards maybe if you have good oil in there already it might be worth changing it out for some running in oil to help the break in process along-- just a thought willy |
| William Revit |
| Willy, I did start with a 30 grade mineral 'brand x' oil but changed it to Castrol GTX along with a new filter after quite a bit of running, although not under load. Maybe this is not helping the situation. I may put some 'ordinary' oil in to see what happens. Is there a recognised brand of braking in oil? Don |
| Donald J Walker |
| I think that there you have the answer - its a good idea to use a proper running-in oil for 500 miles after a rebuild of a classic engine. Regular oil can contain slip additives, friction modifiers, etc., that do you no favours in getting the rings bedded in. Running in oil is specifically labelled as such. Modern engines don't seem to need it, so it won't necessarily be found at your usual supplier, but manufacturers of classic oils all have one. Dave H |
| Dave Hill |
| I have had excellent success using the Flex-Hone (or Ball-Hone) on all cylinder walls (rebored or not). I have gotten "instant" sealing each time on many MG engines. Self-centering so easy to use at home by amateur. And inexpensive, available at auto stores.
I like that it can be used to break the glaze and provide the desired surface finish on "old" cylinders. Detailed analysis on the web site at brush research.com 100% USA made products. No comemrcial interest but a very satisfied user. Dan  |
| Daniel Shockey |
| Don This might be worth a read: http://www.hotrod.com/articles/1818/ I dont know how thorough you were when you did your engine assembly, as indicated rings straight out of the box wont necessarily cut it. Graeme |
| G Evans |
| Interesting reading Graeme but I think I just saw the horse bolting down the road. I accept that I replaced the original oil too soon with Castrol GTX. I will drain and put an 'ordinary' oil in and then take it over to Hindmarsh Island, long straight roads with a few 'hills', and then give it the "30 mph in top up to 50 mph" etc etc. Thanks for all the advice and hints. Regards, Don TF 4887 |
| Donald J Walker |
| Don
I usually use the Penrite one from Autobarn or Supercheap -- just because they stock it here There are probably others better or worse--? The one they keep here is 15/40 which would be fine for your engine As you have already changed the oil and filter out previously you should have already collected any stray visitors so I would be happy to leave the running in oil in there now for quite a while--1000 miles or however long you usually do your oil changes Probably wouldn't really need to fit a new filter again just drain your gtx and fill her up with the running in oil the small amount of gtx in the filter won't be a bother Don't be in a hurry to drain the running in oil out, it'll do no harm leaving it in there Don't be afraid to give her some stick, you've already covered a few miles so a bit of aggression won't hurt Good luck to you I hope this is the answer willy As an aside, on our racer years ago we ran course 50 race oil and molly rings, never ever bedded in properly with this combo We'd pull the heads and poke the bottle brush hone through it with the pistons at the bottom of the bore and wack the heads back on - It would be good for a couple of meetings and then 'the haze' would return Repeated a few times and then just lived with it but I'm sure it boiled down to the oil being (I'll get hung for saying this)-too good--but needed for the application |
| William Revit |
This thread was discussed between 28/11/2017 and 01/12/2017
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