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MG TD TF 1500 - TD temperature

What is the normal running temperature for a TD and what type (rating) of petrol should be used ?

I had some problems with the car starting so I changed the plugs and filed the points, but it turned out to be a stuck needle valve (which I fixed with a few solid raps to the side of the carbs---high tech maintenace --- hugh)

Anyway since I did that the temp has risen above 90C and today it went over 100C. I don't think that's good.

I did use a higher octane rated gas (89-mid range) on last fill up.

I don't think it's the water pump, but then again, I'm not to sure how to check whether or not it is working. Any suggestions on checking the water pump?

The car runs fine, although it may be a bit sliggish but there is no misfireings or stuttering. Just maybe a bit slow on the uptake.

What do you mean by setting the idle at 1000 at 80C? Does the screw adjustment on the on the accelerator armeture that opens the choke have a major effect on temperature?

Thanks guys for your ever appreciated advice--- Bob Fulton

Bob Fulton

Wow, where to start! When the mixture is correct, it should not run correctly, [with out the choke] till it reaches 140 deg.F., or more, 160 is better.170-200 F is normal running temp.Use a breakerless ign. /rebush the distributor.You can not go wrong using the higest octane you can buy.Replace the float needles, set @ 7/16".remove the dashpots & pistons, set the jets to .070" below the bridge. have the eng.block & radiator flushed, & or strip the eng. & have it hot tanked.Adj. ign. timing for approx. 34 deg total adv. @ any thing above 3,000rpm.You may want to start with the basics, first, as in basic auto repair, & or local experts. [Mechanic's take bribes, as in a bottle of wine, booze, or coffee, $, etc. but most will offer free advise esp. when you seem to be intrested in the technical part of the vehicle].Become friendly with your local garage, & their workers! Len
Len Fanelli

Bob, I think the symptoms sound as if your ignition advance may be seized up, making the car run with the ignition retarded. This causes overheating and sluggishness.
This is easily checked with a timing light. The timing should move around the pully quite a way as the engine revs increase. If the timing does not move around the pully you will have to dismantle the distributor and clean up the weights and springs under the distributor base plate.
The temp on my car is normally around 80 deg C.
Also filing the points will change the timing, but only marginally.

Hope this helps,

Paul.
Paul van Gool

Bob,

Timing can be the biggest problem.

If all is well there, take a look at the thermostat. If it is there and working, look elsewhere. If it has been removed, check to make sure the by pass (small line coming off of the top of the thermostat) IS plugged. If has not, much of the water will by pass the radiator.

What is the condition of the radiator?

During summer months my TD runs (at 60 MPH) in the 85 to 92 degrees C with outside temperatures in the 95 degrees F range. I had simular problems. The previous owner had timed the engine with a engine timing light to 0 degrees. This is not the correct procedure. It causes to you be about 7 degrees retarded. You have to either use static timing with a volt meter or test light or a timing light with a dial on it to determine what the advance is at various engine speeds. Advance at 3000 RPMs or so should be about 35 degrees advanced. I have modified (easy to do) the thermostat housing to install a modern thermostat. My by pass line is plugged. I use regular gasoline.

Good luck,
Bill
Bill L

With the temp probe mounted in the radiator, how would the thermostat cause over heating? Wouldn't the block over heating go unnoticed if the thermostat was defective?
My TD has over heating problems also.
Don
Don

Don,

The thermostat does not completely shut off the flow to the radiator. It is a metal to metal seat that blocks most of the flow but not all. The assembly I had has a very loose fit in the closed position. If it fails in the closed position most of the flow to the radiator will be blocked.

Another area I wonder about is the by pass blocking shield. If it does not seal porperly when the thermostat opens, some water will by pass the radiator.

It can be easily tested by putting it and a thermometer in a pot of water and seeing where it opens and if it opens.

I do not think that an installed thermostat is the cause of most overheating problems. Timing, dirty radiator and thermostat removed with by pass not blocked would likly be the larger percentage of culpits. There is also a small bleed hole in the block front to rear passage that has been know to cause problems when it is plugged.

Good Luck,

Bill

Bill L

Bob
I've owned and restored 3 TD's doing ground up on each. I have never ran my cars with the thermostat installed in the engine. My cars do not overheat in the summer. I burn the higest octaine gas I can buy. With out the thermostat installed it is easy to check the water pump, just remove the radiator cap and look to see if the coolant is moving. I also have the by pass pinched over and welded shut. My advice to you would be, If your car did not overheat before, then what ever changes you made caused this problem to surface. Most likely the timming. On the last car , when I started it the first time I use a timming light. The engine ran very ruff and had a noticeable lack of power. I merely turned the distbuter untli it ran smooth. I drive this car all over with no problems. Some times the low tech solutions work much better. Like your thump to the carb. P. S. I know I' will receive a lot of flack over these two, but it works for me.
John
John Hambleton

Bob,

Don't forget about the two (or in some cases one) 3/16in holes behind the two freeze plugs in the water gallery. If timing is NOT the problem, then most likely these holes are clogged with debris. Clearing them will remedy the problem. Do try the easiest things first, though.
Reed Yates

Guys,
Great points, but also remember... if a brake cylinder is hanging up, it will cause "sluggishness" and overheating.

Blair

Blair Weiss

Reed,
I'm owner of a 52 TD an the same problem of overheating at this end of summer. But my english is too poor to understand your world and where I can find these 2 holes. Have you a picture or a photo or an explanation for me ?
Thanks so
Patrice
Patrice Menager

I personally think the importance of these holes is really overrated. How can any significant flow go through two tiny1/4" holes? It cannot. No doubt some are knowledgeable than I, and please correct me if in error- I think the water pump circulats cooled water from the lower rad hose through and around the raised casting in the block rearward around the block, and up, into, and through the head, exiting at the front head outlet. Therefore, there is little to no active flow through the block. The water in the block is somewhat stagnant , with heat transfer by thermosiphon upward. The factory manual refers to the cooling system as "pump assisted thermosiphon" somewhere. Most all of the combustion heat is in the top/head area, particulary around the exhaust valves. If a motor has not been maintained, and/or it has been years since a rebuild, yes rust and gunk can build up at the base of the cylinders and perhaps cause running a bit hot. In this case, opening these holes may assist in flushing/cleaning out gunk. But active coolant flow- I don't think so!!
George Butz

Believe me, those two holes are important - I know from experience having lowered the temperature on my TC from 95 degrees C to 85 degrees C in the summertime here in Mississippi by opening them up. A short article and photos of what I did can be found at: http://www.mg-tabc.org/techn-up/The%20Hidden%20Water%20Passage.htm

Also, although the text says the holes were opened to 9/32nds I actually drilled mine out to 5/16ths. The person who co-authored the article thought that that was a bit large - but it's working fine for me.

Good luck.

Gene Gillam

John Hambleton: Do you actually see water flowing in your radiator top? I don't recall seeing mine move so I wonder if my thermo is seized up? Do the rest of you see circulation in the radiator top? I gues this needs to be checked at about 2k rpm?

Chris
Chris Couper

I do see the fluid moving in my radiator when the water temp is up to 70c.

Don
52 TD #17700
Don

Bob
I also wanted to mention the two holes located behind the core plugs, but forgot to do this before I pushed the "send" button. In Horst Schach restoration manual(page 94 & 95) and W. K. F. Wood's engine rebuilding/ super tune manual, these two holes are discussed in detail. They are usually drilled out when the engine is rebuilt. Some times when the engine over heats this can be the cause or the fix. Also if you read these to references they tell you that: some of the engines have only one drilled out, some none, and some both. On each of the engine rebuilds for my cars I drilled these two holes out after the engine was hot tanked.

Chris- Yes if the thermostat is opened. (Up to temp)

Gene Gilliam nice pic's and I agree with your comments. Ditto on the 5/16 This engine only had one hole and I had to locate and drill the second. It had me worried, that I would drill through the engine , in the wrong place. Read and follow the manual's instructions. Hope this helps!

John
John Hambleton

Another tip: try using Water Wetter. This is an additive to the coolant that will increase heat transfer capacity. It is available at Pep Boys (and I think Moss may carry it). It works well. I use it my both my TF and my Model A Ford. It doesn't correct the basicoverheating problem but it gives you more cushion..
Doug McCord

Bob,

Give us an update on your progress. We'd all like to know what you find.

Reed
Reed Yates

This thread was discussed between 14/09/2002 and 23/09/2002

MG TD TF 1500 index

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