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MG TD TF 1500 - XPAG Smoking away after rebuild.

I had a major issue with my 53 TD a few months ago and lost compression completely on #1. I don't have the time myself at the moment, so had the engine rebuilt. It now runs wonderfully. Upon startup no smoke. However once it runs there is a lot of exhaust smoke. The plugs are covered in oil. My shop is a British shop and used a very reputable machine shop for the rebuild. They are going to pull the engine and see what is going on, but am posting here to see if anyone here has an idea? Valve guides are possible, but the head was rebuilt. Bored, new pistons, rings. A full rebuild by a well regarded shop. (But no XPAG specialists) Its been run now for plenty of time to seat the rings. I am guessing here, but if an early TD banana hole gasket was used incorrectly, could this cause what is being observed?

Thanks much
Simon

S Griffin

Well, I see three possibilities. Oil is getting past the valve stem (what seal did they use on the valves)

Next is a bad head gasket or uneven head/block allowing oil to get in to the combustion chamber.

Third is bad oil rings. As all plugs are oiled, they would have had to install the oil ring incorrectly on each cylinder.
Bruce Cunha

Improperly installed rings either upside down or end gaps not properly spaced, cylinder hone improper for ring type, chromoly rings not seating, cut or improperly positioned intake valve stem seals.

Bill Chasser
TD-4834
W A Chasser

I have exactly the same problem Simon. On start up no smoke, after about 6-8 min heaps on smoke. When driving at up to 80kph, nothing, on slowing and shifting down the smoke returns. I suspect the rings, and the bore is now glazed, I have heard that the Hastings rings I used may be prone to this problem. I have new guides and new oil seals. I will remove the pistons and re-hone the bores and see what happens. I posted on here and had plenty of suggestions but no definitive answer.
Regards, Don TF 4887
Donald J Walker

Remove the oil feed to the head. Block off the banjo with a bolt, nut and fibre washers. Remove as much oil as you can from the head and rockers and run the engine to see if it improves, if it does it is an oil seal problem. The short running time will not harm your valve gear. If you are worried you can run it with the rocker cover off and put oil down the pushrods with an oil can.
We have just done this on an XPAG because "professionals" had managed to build an engine with a 30 thou ring gap .
Ray TF 2884
Ray Lee

Thank you all. I am going to pass the thoughts on to the shop to give them a starting point. The place has an excellent reputation as does the machine shop, but neither are TD specialists.
S Griffin

Another thought, are you using a synthetic oil?.
The rings do not seem to bed in with this type of oil.
Ray
Ray Lee

My first impression- pulling the engine to evaluate oil burning is a lot of work and like cutting off your nose to spite your face, unless they intend to test it on a dyno.

Compression test and bleed down should be first on the agenda. Both will likely be good.

Have you checked to see if the air filter isn't overfilled with oil? It happens. Try draining and running it dry.

Make sure you do have a banjo screw from block to head with a small hole/restricting orifice. As Ray suggests, you may be flooding the top of the head where oil is rising up to the guides. Sounds like a possibility.

Head gasket is not the issue. The banana head gasket concern is much ado about nothing.
JIM N


My bet is improperly installed oil seal O-rings on intake valves. These are somewhat unique to British cars and the installer may no have known that they go under the keepers. I have personally seen this issue before. If there is oil in all of the cylinders then the problem is common to all of them. A head gasket is not related to oil in all cylinders.


Richard Cameron

As Richard says the "O" rings must be fitted correctly trapping the seal between the stem and collet which seals the shroud. If original seals are fitted, see if oil will stay on the spring caps, if not the seals are not fitted correctly. If modern seals are fitted the shrouds must be left off or they just slice through the new seals.
Ray TF 2884
Ray Lee

"Valve Stem Oil Seals"

Check the 2017 archive, it may help you.
R Schappel explains how to fit the seals
Ray
Ray Lee

Make sure the oil shield's are on top of the valve springs not on the bottom (yes it will fit and becomes a dam to collect oil and send it down the valve shaft)
Drawing above shows correct fitting.
Rod
Rod Jones

Thank you all for sharing your expertise. I have passed the thoughts to the shop. Diagnostics will commence on Monday. Hopefully she will be back with me when the weather turns nice.
S Griffin

I agree, compression test and leak down test, both hot and cold, are in order before pulling the engine. Learn what you can while it's still able to run.

The oil shields being on bottom is definitely a problem, but in my experience causes the opposite condition - smoke on startup. They collect oil which slowly leaks down the valve guides while parked, then the first start burns it all out.
Steve Simmons

A continuation from my smoking engine issue. Quick recap. This engine has been completely rebuilt by a reputable machine shop, but not one steeped in XPAG tradition. They are convinced that the head is done correctly. Compression test is good on all. Look what the pistons look like when the head is pulled. Oil pooling on top of them. No wonder this thing smokes like crazy. It can only be coming from below or above, Machine shop has taken the head to check, but is there anything else this could be? The engine was completely redone with new pistons, new rings, this just does not make sense to me.



S Griffin

I had EXACTLY the same problem and also after a rebuild. It was my fault I had positioned the valve stem oil seals in the wrong (but what looks like the correct) place. Befor you do anything drastic run the engine for a few minutes then take off the rocker cover. There will be a small pool of oil in the top of the valve collet retaining "washers". Leave the engine for a while and look once again. If any of the pools of oil have drained the stem seals are your problem.

I fitted Mini seals and the problem is totally curred.

Jan T
J Targosz

Morning

I had the same problem twenty years ago after a restoration of my TD. I turned the engine over to a local builder of scca race cars for rebuild. I however kept the carbs, water pump and oil pump for my own work. Once the engine was reinstalled and I started it and it ran fine but then started to smoke. Oil pressure was about 60 which sounded great. Took the engine back to the builder and after a lot of checking found that the oil pump pressure relief spring had been streached some time in the past to increase oil pressure. It never dawned on me to check for it. The builder installed a new spring and the engine has been fine for 43k miles since. Sometimes it is the simple thing that bite us.

Good luck and Safety Fast
Dick 20102
R McCutcheon

From the picture it could only be the valve seals or valve guides. Do you have bronze guides? Did the machine shop hone out the guide to the proper clearance? I had the exact same problem with pooling oil on the piston surface and it was incorrectly installed valve seals. But if the guides have too large an ID oil will flow into the cylinders. If you look in the intake ports you will probably see signs of oil leaking past the valve guides.

Tim
Timothy Burchfield

This thread was discussed between 15/02/2018 and 21/02/2018

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.