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MG TD TF 1500 - Hot TD

My TD has always run hot since its rebuild. I am getteng better gas milage than other TD's whose owner I spoke with. Does this indicate running too lean?

I am using a little coolant somehow but don't see any white smoke or under car leaks. My question is: Do I have a small leak between the water jacket and the combustion chamber via the head gasket? Could this be making the car run hot? Thanks, Tom
Tom in beautiful upstatre NY

Tom - double check the orientation of your fan blades. I would also suggest you remove your grill slat set from the outer shell and see if that makes a difference. Many cars seem to run hot due to aftermarket grill slat sets - which are not the same as the originals - the originals were more open when looking at them head on.

If you are loosing water, you may want to see if it is simply spitting it out due to expansion. Can you give us a little more info - how hot for instance. What do your spark plugs look like - are they showing a lean condition?

Jeff
Jeff

Tom - I am with Jeff regarding the loss of coolant. If you keep topping the coolant up every time you find it below the top top the filler neck, the system will keep forcing it out every time the coolant heats up and expands. See the article, Expansion Tanks, Coolant Recovery Systems, and How the Cooling System Works in the Other Tech Articles section of my web site at: http://homepages.donobi.net/sufuelpumps/

As for the issue of temperature, keep in mind that an engine is not over heating as long as it is not boiling (no steam issuing forth) and the engine is not stumbling while the car is moving. You also need to check the actual temperature of the coolant with a candy thermometer or such to insure that your temperature gauge is not lying to you. To give you some perspective, our TD coolant temperature stabilizes between 90C and 95C and the car runs fine at that temperature. Cheers - Dave
David DuBois

Mine used to run hot. The fan blades were correct, but the slats were blocking the radiator. I adjusted them (mine were riveted top and bottom and would pivot), to allow more air in. Look at some photos and then adjust to that.

However, I notice that you are in a cold climate and may have a heater installed. Mine at one time had, but it was removed and bypassed, when I got it. They had a takeoff for the heater at the plate on the back of the head. When they removed the heater they ran a hose from the front of the engine to the back of the head. This effectively bypassed the head and messed up the cooling. I put a solid plate back on the rear of the head, and it is much cooler, and more stable now. I don't think a heater should ever be connected to the rear of the head on these cars, but I'm not sure. Certainly it shouldn't be bypassed as mine was.

Larry
larry Ayres

Hey guys, thanks for the replies. The car often runs hot enough that the gauge needle poins to the second 100! I will check the plugs tonight for color & ash. The fan blades are correct, the "hidden water passage" has been cleaned out, water wetter installed, bypass blocked, waterpump replaced and timing re-re-re-re-adjusted, all to no avail. The grill slates are twisted wide open in the front.

Now that its cooler in NY, I don't have a problem until Spring. :). Usually, the car runs 10 to 15 degerees hotter, in celsius, than the air temp in fahrenhite. Regards, Tom
Tom in beautiful upstatre NY

Tom, look inside the top of the radiator. You should see three rows of vertical tubes looking from front to back. My TD always ran hot until I had a shop replace my two row rad with a three tube. Now, it runs most all of the time right on 85C like it is supposed to if the thermostat is in good condition. Thats another possibility for you to check.
Jim Merz

Thanks to Jim Merz for the radiator clue. I find that the TD has 2 rows of ovel shaped tubes, not 3.
Is a three row "core" easy to source? Thanks, Tom
Tom in beautiful upstate NY

Its something that the rad shop would replace your original with...
gblawson(gordon)

Tom,

As Dave Dubois suggested, check your gauge. Either put a Candy Thermometer in the coolant in the neck of the radiator, or run the temp sensing bulb of the gauge into a pan of water and boil the water. If the pointer is in the wrong place, it is easy to reposition.

warmly,
dave
Dave Braun

Tom, my radiator shop apparently had no trouble obtaining a 3 row radiator core from his supplier which was in Ohio I think. It looks essentially the same as the two row.
Dave B, I did check my radiator with a candy thermometer before I had the core replaced. My temp gauge was showing the correct temperature.
Dave D, my coolant thermostat is supposed to maintain a normal running temperature of 85C which it does very well. Driving up a long hill will make the temp increase to about 90 but quickly goes back to normal when the extra engine load is relieved. Summer tempeatures on St. Louis highways can be brutal to our little cars.
Jim Merz

Tom... you mentioned 'the bypass is blocked'.... what did you do to the bypass and why?
gblawson(gordon)

Hey Guys, I was advised at a GOF to block the bypass as I was not using the original "sleeve" type thermostat. ( It made no difference) I was advised at MG 2006 to remove the thermostat, I did & it made no difference. Water Wetter, no difference. Radiator boiled and rodded, made no difference. The block was hot tanked at rebuild. The temp guage tests OK. This winter, the radiater come out and/or I get the one Shade Tree has, if it has 3 rows. Any advice or logic welcome. BTW, the TD keeps on going, hot or not. Tough little motor. Regards, Tom
Tom in beautiful upstate NY

Tom, if it is not emptying the radiator, smelling over hot or actually boiling I would not worry about it. The old adage "If it's not broke, don't fix it" is often very appropriate. Regards, Richard.
R Payne

Tom, the engine needs some kind of thermostat to achieve optimum running temperature. I prefer the original type but a more modern replacement will do. Better than nothing. When using the "sleevless" thermostat, I read somewhere that a small hole (1/4"?) should be drilled in the center of the bypass blocking plate. This only allows coolant passage when the thermostat is closed on a cold engine. When the thermostat opens, the coolant flow takes the easiest (largest opening) path. This is about as close as you can get to the operation of the original type thermsotat.
My two row radiator used to heat up to 95+C on normal highway driving and even higher on hills. I have always used an original type thermostat.
Jim Merz

Forget about the gauge being accurate- that only measures one small and possibly irrelevant spot. Using no thermostat will make it take way too long to warm up- thick oil, longer with choke, and/or run too cool. Need some hole in the bypass. Find a shop with a CO sniffer or emissions tester. That can test for CO (or exhaust gas) in the radiator. Hard to read plugs like in the old days due to lead free gas, but I think if it is running fine it couldn't be lean enough to run hot. Did it run hot before rebuild? Candy thermometer is OK, but You can buy a hand-held IR thermometer for about $65. You can shoot the rad, block, and everywhere to see how hot various areas really are. Remeber the circulation in the XPAG- out rad. bottom to water pump, then back through the "bypass" channel in the side of the block (the raised area), then up the back of the block, up into the back of the head, then forward and out of the head into the thermostat, back into the rad top tank. With the hand-held IR, you can shoot the temp all along the way, and for example check the water temp. in various parts of the radiator to see if any blockages. Most likely a false reading, possibly something blocking a water passage, or a headgastket leak if really hot. George
George Butz

Can someone direct me to the technical site which shows how to drill out, 'the hidden water passage'?
Thanks,
Scott
SRBarrow

Scott,

I read about this long ago on a site devoted to an XPAG rebuild for a TC. Here is a picture of what I did. Note that the rear hole was visible, and that the point is to provide a similar hole 3/16 in diameter in the front of the block. Since you are drilling through a wall in the block casting, when the drill goes through, you will feel imediate relief, and hit something hard. Stop drilling at that point.

I'm not really positive that the fix as necessary, although on my rebuilt engine, developing more power (hence more heat) I'm running cooler than before, by about 15 degrees C. I also Jet-Hot coated my exhaust manifold, and rebuilt my water pump. Note that the water pump would have little effect at high speed.

warmly,
dave


Dave Braun

Scott,
Years ago, a friend bought a TC that always ran too hot. He tried all of the things you described and got the same results.

What he eventually discovered was that the cylinder bores were too tight. You might want to pull the head and measure the bore diameters and compare them to the current piston size which is probably stamped in the tops of your pistons. If you weren't having a temp problem before the rebuild, I'd be very suspicious about the quality of the work...

FYI: There's a table in the factory service manual on page A.13 that gives diameter ranges/oversize piston sizes.
Terry McArthur - 52 TD

Dave... so you clean out the one by redrilling and add another at the front?
gblawson(gordon)

Gordon,

Yes, that's correct. It is relatively easy to find the rear hole just by probing with a pick. We had to drill the front hole from scratch.

dave
Dave Braun

I found it on the site: www.mg-tabc.org
SBarrow

My early TD had no water temperature guage, and I drove the car for a good number of years without wondering about it. I came across a water guage [NOS] and installed it on the stearing column behind the facia. It is only visable from the drivers position if you look in the right place. While I still have no overheating problem, I find I am looking at it more often than the oil pressure guage. I sometime think that old caution as quoted above by Richard of NSW, Australia,"If it's not broke, don't fix it", is true. I do appreciate that those in the southern climates, can not take the same attitude as I, at 52 degrees north,altitude 4500 ft.
George Raham
TD 4224
G. L. Raham

This thread was discussed between 17/10/2008 and 31/10/2008

MG TD TF 1500 index

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