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MG TD TF 1500 - Smoking again (still?)

My early TD is now running great but an old problem is still with it.

It was burning oil when sitting at idle. OK this had to be valve guides, right? Anyway I have checked everything over just in case, compression is great across the board, engine had new rings and bearings approx 3000 miles ago, cylinders were carefully cross hatched, valves were checked and re-seated to the head but head was put back together as it came apart (bad move). All indications pointed to valve guides as it didn't burn any oil when running, only at idle. I pulled the head, prepared to install new valve guides but there was virtually no movement of any kind and guides look fine. What I did find was that the metal "cones" were installed at the base of the spring so it effectively collected oil and would pump it down the valves. The workshop manual should have been referred to previously and it would have been caught then. So new umbrella seals installed and cones removed. Once it was all back together the engine was fired up and no smoke, short drive and then let it idle in the drive and all was good!

Took it into town the other day and it starts right up with no smoke and it is fine while driving but the first stop light resulted in some smoke and each stop after that results in bigger clouds but once again it clears once you move off and there is no smoke while driving. The oil pressure sits at just over 60 when running and the top end of the engine seems to get a lot of oil running around in there.

Any ideas as to what I am missing or should I still be looking at the guides?

Thanks
Brian
Brian Smith

Hi Brian;

When you did your engine overhaul did you inspect the oil pump? Specifically, did you check the length of the oil pump pressure relief spring? You may have either a streached, modified or different pressure relief spring installed to recover some oil pressure on the worn engine. Overhauling the engine negates the need for the temporary "fix". Ask me how I know. I had a similar problem with my rebuilt engine which had 60 psi oil pressure and smoked at idle. Installing a proper length spring solved the problem.

Good luck.
Safety Fast

Dick McCutcheon
Dick McCutcheon

Dick

Thanks, I installed the original spring even though I have a new one sitting in my parts supply. I will change it and see what happens.

Brian
Brian Smith

Brian; A couple of things come to mind. Excessive oil amounts in the rocker area could make it difficult for the seals to control. Worn rocker bushes and shaft could let lots of oil run amuck in the upper valve train. Should be accompanied by excessive rocker noise even after valve adjust if this is the case. Restriction in the oil feed line to head may be missing or drilled oversize-check archive for discussion of this.
Have seen valve guides knurled as a means to tighten clearances-guide will look like it has a spiral cut into it on the inner surface. Valve will feel tight in guide-but the knurl serves as a conduit for oil to run down the guide. Used to be a cheap patch for worn guides. You mentioned umbrella seals-the type that moves with the valve stem or the type that is pressed on the upper end of the guide? The latter type is much more effective for oil control.
At least you are doing some mosquito control while you work toward a fix--poor attempt at small humor.
Dan Craig
D.R. Craig

Worked on the TD today and talked to the parts supplier I have delt with for years. They suggested that the oil line from the block to the head should be blocked and then a small hole drilledin it so that the amount of oil to the head is limited. Once this was done I fired up the car and ran it until it was really hot and no smoke at all, then it suddenly began to smoke...a lot! I shut down, waited just about one minute and started up again and once again no smoke???? Left it running a while longer and it started smoking again like crazy so once again I shut down.

This time I pulled the rocker cover and there is a large amount of oil still around the rockers. Checked the valve clearances hot. Cleaned up the cork and reinstalled the rocker cover and once again fired it up and there was no smoke. Left it running again for a while and smoke again. This one has me stumped! If it was burning oil when shut down, why does it not burn it when I fire right back up???

With the oil line to the head, I blocked it right off and then drilled a 1/16 hole as this was the smallest drill I have. Should this be even smaller?

Brian - stumped in Campbell River
Brian Smith

I don't think I would go any smaller... I know that was a way to get a higher oil pressure reading in the old days? You don't want to starve the upper end... worse problems would occur!
gblawson(gordon)

While I'm no expert, your "why" seems to be pooling of oil on top of the head - it's not draining back into the crankcase fast enough. After you shut it off, it has time to drain. After running a while, it pools up again.

Solutions? The details must be in the archives here, they've been mentioned above. Just trying to help you get your head around the problem first.
Tom

Lots of great comments and I think that I may be onto the cause....finally. As compression is good across the board I have ruled out any ring problems. With the oil line restrictor in place I still get an abundance of oil in the rocker area and as indicated above by Dan Craig it appears that the rockers should be rebushed as even when adjusted properly there is a lot of valve noise so this will be on the agenda.

The latest possible cause of the smoke was again alluded to by Dan Craig and my new neighbour, a mechanic for 35+ years with lots of British car experience. My neighbour is 90% sure that the problem may still be the seals. The new umbrella seals I purchased do fit down over the guides but are free to move up and down with the valve. I am told that this is fine with the exhaust but the intake should have umbrella seals that "fasten" to the guide so that they actually scrape the oil off the valve shaft. I am told they are called positive seals and have some sort of metal keeper to attach them to the guide. I will be sourcing these and hopefully report back that the outcome is no oil smoke :>)

Brian
Brian Smith

"Dick McCutcheon, Stuart, Fl., richmccutch@aol.com
Specifically, did you check the length of the oil pump pressure relief spring? You may have either a streached, modified or different pressure relief spring installed to recover some oil pressure on the worn engine. "

This is very interesting since I have not heard it before and I do have occasionally a white cloud after stopping and idling. I do have that adjustable oil pressure regulator at the bottom of the oil pump and I will start experimenting with it. I currently at 40-60 psi.

Thanks for the idea, Denis, 1950 TD
Denis L. Baggi

If intitally replacing the seals cured it for a time, likely that is where the problem is. I'm no machinist, but I'm sure the modern seals are suppose to grip the guide and not move, with the movement between the valve and seal only. Most important with the intakes. I think the rocker area is suppose to be well-oiled- this helps with cooling. I'm not sure what oil pressure has to do with burning oil, unless the area under the valve cover is being totally flooded with oil. George
George Butz

I agree with George, there should be no connection between oil pressure and burning oil,,,, oil pressure is at the bearings, being forced through them. Whereas the oil under the valve cover is just driped out of the rocker shaft to drain back down the return holes,, There should be no pressure around the valves and seals.

SPW
Steve Wincze

Put it together with the line temporarily blocked off to the rockers. 30 minutes running without oil to the rockers will not harm anything.
A few years ago we as a club went from Tampa to Stone Mountain Georgia. One of the card a 52 TD had just completed a major rebuild of the motor. about 200 miles into the trip it had a squeek in the valve train. We pulled the valve cover and it was very low on oil. Some oil was poured over the rockers and every 100 miles for the remainder of the trip this was repeated.On arrivasl at Stone Mountain we pulled the rocker assy off and found that he had transposed two rocker supports and the one with the oil gallery was out of position. On examination of the rocker shaft and bushings we could not discern any wear.
That is why I said put it together and run it a few miles with out oil to the top. this will immediately isolate your problem.
Sandy Sanders
Sandy Sanders

Again lots of great comments! I have confirmed that the smoking is due to the guides, even though they appear and feel tight with no movement that can be detected. The problem now is that I have been unable to source a positive seal for the valve stem that will clip or fasten to the guide. After checking the size of the valve stem it appears that the ones mentioned in the archives (chev 140 4 cyl engine) are too large for the early TD valve stems as they measure .314 in and I believe the chev ones are .385. I gave the local suppliers the Felpro number ss72522 and one had them the other crossed to a Victor # but both are just a plain umbrella seal that you push over the guide. I am assuming that it floats up with the valve, especially when the engine is hot.

One outcome that the archives hinted at and helped solve was a strange clacking coming from the front of the engine. This had worried me but always went away when the engine revved a little but returned on idle. Someone had a problem a while back with a valve pushrod being slightly bent that clipped the side of the hole and the fron one on my car was extremelly close as I turned the engine over with the hand crank. I pulled the valve gear and it had a small polished area on it so I switched it with one that had a lot of clearance. Of course one thing leads to another and I checked all of them and did some more switching, the end result was that the car would not start.....very strange. Checked the valve clearance and they were now all out of adjustment???? Looks like I have a couple different sized pushrods in this engine. Once adjusted it once again fired right up and the clang was gone, still smokes if you leave it idling until it gets hot but not while running.

I have a new set of valve guides but am really hoping to get some more mileage out of the ones in the car now. Also I reported that the compression was 145 across the board in error, it is actually 140 across the board with the carbs wide open and all plugs out.

Brian - killing lots of mosquitos for now
Brian Smith

Brian; Fellow who writes on the Austin America website has been selling a variety of on stem seals on ebay. Has a nice article on that website about seal issues. He might be of some help suppling seals for your application. www.austinamericausa.com in Google should get you there. Dan
D.R. Craig

Thank Dan, I have now contacted him and hopefully he will provide some insite.
Brian
Brian Smith

Does he have the seals to fit a TD as I would also like a set if he does

Clive
C.Skelhorn

Clive

I sent him the measurements for my TD, a 1950, and he had a set and has now sent them to me. Should be here early next week and I will install and let everyone know how well they work. You can email him at austinado16 at cs dot com and his name is Todd.

Brian
Brian Smith

Brian,
The pushrods will always be of different lengths when in used condition because of wear. When they are removed from the engine, they should always be marked so they go back in to operate the same valve that they operated before removal. If you don't follow this rule, you will have to adjust each valve clearance again on reasembly. There is also a problem with the "bell shaped" end of the pushrod fracturing a bit, so it is almost impossible to adjust with normal feeler gages. This will result in a noisy valve as you encountered.

SPW
Steve Wincze

Brian,
did you install them yet, I have just received my set today and they certainly look as if they may help.

Clive
Clive Skelhorn

HI Clive

It looks like you may get them installed before me! I haven't received the seals yet but hopefully within the next few days.

This last weekend we took the TD on a 3 day tour on Mid Vancouver Island with the Vancouver pre56 MG Unclub, Old English Car Clubs from Nanaimo, Victoria and Comox, members of NAMGAR and the Campbell River British Car Club (our home club). The car ran great with the exception of smoking on idle so I am really looking forward to installing these as I have killed enough mosquitoes now.

Brian


Brian Smith

Clive

Still haven't received my seals. Have you had a chance to install them? Please let me know how they work.

Brian
Brian Smith

Well the seals arrived and I have installed them. Once fired up the car ran great and no smoke.......until it got warmed up and then it began again. Looks like I am going to have to take it apart to find out what is going on.

On initial fireup, the engine sounded quiet and smooth and there wasn't any smoke at all but once it had idled for about 5 minutes the engine suddenly became noisier, the smooth running changed to a miss and the engine began to smoke.

Brian
Brian Smith

I recently did a umbrella type seal replacement on my TF and found that all of the idle oil smoke and low speed plug fouling has gone away. I used the Felpro umbrella seals that fit on the valve stems. The old rubber sleeve seals (not o-rings) were removed along with the metal deflectors.
Using 20W-50 oil, I have 75 psi on cold start up, which I belive is the max. limit for the bypass valve.
Engine runs 60 psi @ 3000 rpm hot. These engines have a pretty copious volume of oil in the valve system when running.
This engine has 44.000 miles on it and has never been apart.
colin stafford

The new seals are a metal jacket positive seal with a viton seal that has a spring keeper around the top portion where it goes around the valve stem. The Felpro style didn't work either.

I am open to all comments now as I don't understand why a cold start would be quiet with no smoke but once warmed up, 5 minutes at idle, would result in lots of smoke, rough idle and noisy engine. I am not thrilled about pulling the engine at this time but I am also not sure what I am looking for. I would think that a cold engine should be noisy, rough and smoke too!

I have run it with the air cleaner off and the rocker vent open to see if that was part of the problem but it makes no difference.

Sure glad that we have this group of enthusiasts.

Brian
Brian Smith

I have now tried a couple other things. Sandy, you mentioned running the car with the oil line to the head blocked, I tried this and it actually ran longer before starting to smoke and then when it started smoking it wasn't as bad although I wouldn't want to be behind me;>)

I then hooked up the oil line again and started the engine, once again no smoke initially but when it started to smoke I added some bardahl that is supposed to eliminate smoking and leaking. I added it while the engine was running and watched the amount of smoke and it decreased to the point where there was hardly any smoke with a hot engine.

I am not sure what all this points to or if this has "solved" the problem but I will be taking it out for a run within the next few days and will report back the results.

I have been contacted through my email from a few individuals and they have all pointed to a possible problem with the head.

Brian
Brian Smith

I have driven the car around and while it still smokes a little bit at idle when hot I am not getting the clouds anymore. The symptoms are better, now if I can just determine the cause all would be well.

Brian
Brian Smith

Brian,

It sounded all along that you had excessive clearance between your valves and guides, allowing oil from the head to migrate to the combustion chamber. The warmer the engine, the better the oil flows, and the more likely it would draw down the valve stem or the guide. The Bardahl product you used probably did the trick, although I owuld imagine its effects to be temporary. From the Barhdahl website:

"The ORIGINAL Smoke Treatment ! Extra thick formula seals the spaces between valves and guides, between piston rings and cylinder walls, thus reducing oil consumption and burning. Improves compression, power and performance, cushions worn bearings and quiets noisy lifters. It is the most effective additive for oil burning cars to reduce exhaust smoke."

I don't know if you are using the three or four ring pistons (the fourth ring is another oil ring at the bottom of the skirt) and if the rings were properly gapped on installation, and whether you did a compression check hot or cold, so I can't rule out rings, cylinder walls, bore sizes and pistons. I also didn't see what oil you are using, and if you are using an additive for flat tappet wear, but just assuming all that is correct, I think you need to replace the valve guides for a long term fix.

When I rebuilt my engine, I replaced the valve guides with bronze/silicone guides, taking care to ream them out slightly larger than cast iron guides. I also replaced all the valves, intake and exhaust. (note: there is some controversy regarding bronze guides and their expansion coefficient in cast iron blocks, I'll go on record as saying that properly installed, I believe they perform better than cast iron guides) John Twist says if you are using cast iron guides to have a stem clearence of 0.001-0.0015 inches, and if using Bronze/Silicone to have a stem clearance of 0.003-0.004. The valve stems have a 0.315 nominal diameter. Make sure your valve stems still match this spec.

I hope this helps,
dave
Dave Braun

With multiple sets of seals, and still smoking with the head oil line disconnected, I suspect rings or something else casuing some of the smoking? Even with correct honing, the new rings must have proper clearances- end gap as well as piston skirt to ring. If it starts running rough, that sounds like a plug fouling? Suggest waiting until smoking , shut down and pull the plugs. Are all 4 equally oily? Oil treatment a good idea- cheap and not time involved! George
George Butz

Brian.
Another thing came to mind. If you have the original oil bath type air cleaner on the carbs try running it when the filter is out, Years ago I was following a friends TD to clearwater Beach and it started to lay a smoke screen down so thick that the city police pulled him over. He towed the car home and started checking. Without the airfilter in place it would not smoke. Apparently he had a little too much oil in the filter.
It is now about 15 years later and it still does not smoke at all.
Sandy
conrad sanders

Brian,
I might have missed it somewhere in the long thread,and I might be way off, but may I ask what color the smoke is??

Your comment "I am open to all comments now as I don't understand why a cold start would be quiet with no smoke but once warmed up, 5 minutes at idle, would result in lots of smoke, rough idle and noisy engine"

If you are leaking oil into the cylinders, I believe it would smoke all of the time,, Are we sure it isn't a head gasket problem??
Steve Wincze

When I took my compression readings the engine was cold, all plugs out and carbs wide open. The new rings were gapped according to the manufacturers recommendations. I ran the car into town and back with the air cleaner off the car and it still smoked at that time.

As the bardahl did considerably decrease the smoke I think that I may have to replace valve guides and possibly valves. The plugs were evenly fouled. I have been using Penzoil 20w/50 the same as used in my MGBGT. The smoke is kind of white and removal of the head didn't show any indication of leakage.

I really appreciate the comments from everyone and may end up running it for the summer as is. My B GT is running great and my TF is quickly getting down to the frame.

Thanks All
Brian
Brian Smith

White smoke? Usually oil smoke is white but bluish tinted and smells of burned oil. Are you loosing any coolant? George
George Butz

Brian,
Like George says, burning oil will produce a blue smoke,, while coolant will produce a white "smoke", Run the engine with the rad cap off,,, do you see any bubbles rising to the surface inside the rad ?? Some of your indications are leading me to believe it might be coolant "smoke",,,

SPW
Steve Wincze

George and Steve, the smoke I described as "kind of white" but is actually tinged a little blue, almost grey. The collant level, once it stabilized has remained constant with no bubbles. I haven't had to add any coolant since last Fall. It does smell of burnt oil. After a run of a few hundred miles I will usually have to add about 1/2 litre of oil, at the most.

Brian
Brian Smith

If it smells like oil, it's oil. Really sucks to have a problem like this, but there's a reason, you just have to ferret it out. From what I've read so far, it sounds like an inspection and a little work by a good head man, using the clearances described above, will fix it. If not, pull the engine and go from there.

But since the additive is making it livable, drive it through the summer and have fun. You did get lubrication back to the valve train again, didn't you?
Tom

Checking the archives I came across this very interesting one. But the story stopped before the (happy) end. Brian, could you solve the issue and in what way??
Greetings, Huib
Huib Bruijstens

This thread was discussed between 26/05/2008 and 16/11/2012

MG TD TF 1500 index

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