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MG TD TF 1500 - blue smoke

I 've asked this before but still have not resolved the problem. After my car warms up to 170F, it intermittantly blows off blue smoke while idling at stop lights. It does not do it when cold and is worse on hot days. There is no water in the oil to suggest the head is loose and the smoke is blue grey and not white. The carbs seem to be adjusted fairly well and the idle is smooth although if the car idles more than five minutes it gets a little rough and has stalled out once or twice. It improves for a short while if I clean the plugs but quickly returns. The plugs have black deposits on them and there is some oil on the threads. The original air cleaner was replaced with oiled mesh types and there is a 1/4 inch hose connecting the valve cover and the left air cleaner. There is a loosely fitting filler cap with no breather valve and there appears to be no blockage between the tappets and the vent pipe. The engine has 2000mi after a complete rebuild. Any thoughts?
Russ Oakley

This could be a worn rocker shaft and bushings, as well as old type valve stem seals. The worn shaft and bushings allow an abundance of oil in the vale cover chamber, which is drawn down the valve stems. Generally shows at idle, or directly after, such as leaving a traffic light. It will be worse at warm conditions due to the thinner oil.

D C Congleton

Russ. You may be getting oil through the valve cover into your carbs. I used to run pancake air cleaners with a similar hose, Oil would collect in the hose and periodically get enough to cause a puff of smoke. Moss used to make a plug for the valve cover that had a small hole to allow the valve cover to depressurize. I have one and use it when I am running the engine to work on the carbs.

Might want to build a similar plug and see if it still smokes. That would at least eliminate one potential.
BEC Cunha

Russ. I would suggest the you go over the carbs completely. The fouling suggests that you are running too rich and that could give you an impression of blue or light colored smoke.
Make certain that the float level is correct. Using a bar to set the level is not accurate enough. Remove the piston damper anc actually check the fuel level
(with the key on) It should be 1/16" below the bridge.
Note that the thickness of the gaskets that mount the float body to carburettor have a direct control of fuel level.
Sandy Sanders

I had a plopping, blueish exhaust and faltering idle recently. The reason was insufficient fuel supply due to a half blocked fuelfilter.
I thought the worst, but after cleaning the filter everything was alright again. My fueltank is a bit rusty, so I suspect I will have to repeat this exercise.
Sooty plugs are mormal after even a short time of idling. A little blue smoke from the exhaust seems to be quite normal, if the engine is not reconditioned recently.
Only my experience
Frank van Geldern

Russ....I have that problem with my orig. 44,000 mile engine. I have, what I think excessive amounts of oil that go into the valve train/cover area. Plus the O-ring/deflector on the valve stem is probably long gone. Need to replace with new Teflon/rubber umbrella seals.
My carbs are set on the rich side and I do have fouling problems if I let the engine idle too long.
However, my engine runs really well, does not overheat.So, well left alone.
Colin Stafford

The problems of smoke and oil seal is one and the same.
On our TF, excessive oil worked up through the valve seals and oil ways and deposited in the low pressure rocker cover area, it then was sucked into the carby with the breather tub on it, restricetd the air flow to that carby as the oil soaked into the foam filtering reducing the air flow resulting in one carby running rick. The smoke was grey white and foul at idle, so - part rich mixture, part oil burning off through the carb and into the engine was the prob. And so the plugs oiled up as the carby sucked the excessive oil into the cylinder head. When I rebuilt the motor I, naturally, replaced the oil seals and placed new valves and valve giudes (as they were worn). The problem has gone but I did increased the vent size of the inverted castelated filler cap with a thicked but channeled press down cork seal. (raised it appx 2mm)
ken lees

I think Sandy may be right. I am not burning oil very fast so I think it is running rich at idle. It seems fine when under way. I also notice that the fuel pump clicks at almost 2 clicks a second at start up. It does not seem to be drawing air. I am going to take the pump apart and see if throw over is adjusted properly. I suspect the pump may be building up excessive pressure and blowing fuel past the float needles. I let you know what I find.
Russ Oakley

I took the fuel pump apart and found that I had put the middle casting in upside down. Corrected, I only get one click per 10 seconds on the pump. The fuel level in the floats is 1/16 below the bridge in the carbs but I am still getting smoke when the car is fully warmed up. None when cold, even with the choke out. This time the plugs were lightly black but the threads had a little oil on them. I went through a 1/2 quart of oil in about 500mi. The engine has 2100mi since a complete rebuild. I'm beginning to suspect the valve seals since a compression check show 135 on each cylinder. Can I get at the seals without removing the head?
Russ Oakley

Yes, you can put new seals without removing the head, I have done that often. You have to remove the rockers first, completely. You need an air pump that plugs into the spark plug opening to keep the valves up with air pressure, then with the special lever you can press down each valve, install the seals and put back the top. Generally it is enough install the seals on the intake valves.

However, problems caused by bad valve seals produce smoke through the tappet chest exhaust and not necessarily from the engine exhaust, so you might have another problems.

Seals are sold by many MG part dealers, though I have used those of the Toyota Nita for years with success.

1950 TD
Denis L Baggi

This thread was discussed between 04/09/2007 and 16/09/2007

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