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MG TD TF 1500 - Occasional overheating

My car normally runs, after warm-up, with temperatures of about 70C at the radiator, 70C at the back of the head and 70C of oil at the sump - yes, I have three temperature gauges on the dashboard! (and more). It overheats only if I enter a highway and drive for say 20 minutes at 125 kph and 5,000 rpm's: then, the temperatures are 90 at the head, 80 at the sump and over 100 at the radiator, even though it does not boil. At that point, I exit the highway, reduce the speed to say 75 kph at 3,000 rpm, and temperatures go back to normal. That behavior has almost nothing to do with outside temperature.

To this I must add:

- I have the original 5.125 bridge at the differential, which produces high rpm's: bad for my engine, but a lot of fun!
- I have a Kenlowe electric fan that switches in when the head temperature is about 70
- Spark advance is just ahead of TDC at 700 rpm and goes up nicely as I give gas
- Mixture is OK, perhaps a bit on the rich side
- The water in my radiator is clear, no sludge, just the color on the antifreeze, and I have no consumption thanks to an overhead return tank
- the head is modified about Stage 2 with large valves and higher compression.

I have already asked some specialists whom I thank, and got the following suggestions:

The water pump (which has no blades) turns too fast and produces cavitation, foam instead of water flow: some race cars have that problem and the cure is a larger pulley. But I doubt that applies to a TD and I assume (!) the water pump was designed properly.

The distributor shaft is loose and there might be no spark advance at high rpm's. I will check that, but I doubt because I normally see with a stroboscopic light that advance is fine, actually I can augment it from the dashboard (dangerous, I once melted a piston with too much advance).

So my question is: Is the behavior of my car normal? I would almost think so, those cars were not meant to run at such speeds for a long time. In fact, all members of the Vintage MG Club of Southern California have differential ratios of 4.55, 4.3 and even 4.1 to prevent high rpm's.

If so, is there anyone who has had that problem, and solved it? Maybe with a different radiator?

Thanks, Denis

P.S. My apologies if I might be slow in answering since I will be traveling soon, but I will try to access this forum as much as possible.
Denis L. Baggi

Hi Denis,

Before I tore my car apart, it behaved much as yours. Elevated temperatures (I only had the standard temperature pick up though) at high speed (70 mph) which would go down at cruising speed (45 mph).

Two thoughts, first like a man with two watches you may have too much information at your disposal! But on the other hand, you have a high degree of accuracy and thoughtful analysis, and I know you like to drive the car quickly. I would submit to you that the 100 degree temperature is not that detrimental since you are not boiling, and heat transfer is still taking place. You don't say what antifreeze percentage you are running, but reducing it to 25% will enhance heat transfer even more, but reduce freezing and boiling protection. Since 100 degrees seems to be your max, you will be quite safe on the boiling, I don't know how cold it is where you store your car or how much you drive it in the winter. Secondly, the vast majority of our cars' cooling is via thermo-siphoning, or the natural flow of coolant through the engine due to temperature profile, than from the admitedly inefficient water pump. The pumps are more suited to low speed use, but their flat blade impeller and crude design limit their high speed use. I would do a the of pulley change, as low speed cooling (and idle) won't significantly suffer since you have an electric fan and you run quite cool at low speed.

I think your best bet would be to increase the capacity of your radiator, with a more efficient core and a larger area. You could have one custom built out of aluminum to take advantage of your electric fans and the space available between the grille shell and the pump. Make sure your bypass pipe is completely closed off for high speed running (but you want some bypass during warm-up) perhaps a manual system could be installed. Add an oil cooler If you don't have one, and disable the fan system during high speed running to maximize airflow at speed.

The final advice is to drink plenty of liquids and wear cool clothing while high speed running. If you're cool, you will feel better about your engine! (tongue firmly in cheek)

warmly (or cooly)
dave
Dave Braun

Dennis,

If you drive at or near 125 kph with any regularity, you really should consider a higher gearset. I was lucky and found a Twin Cam 4:10 set, but the 4:30 gearset is nearly as good and much more common. having said that, I realize you probably have climbing issues in the hills and mountains where you live, and may need something closer to the 5:125.

I do not have a temp problem, but I am also planning to install the plastic MGB 7-blade fan, more for safety than cooling. I am told that this fan moves a lot of air.

Tom
Tom Balutis

Denis,

I have made many of the mods you have made, and can confirm that my engine runs at temperatures similar to yours, however I have the benefit of the 4.3 cwp.

In 2006 when driving to Gatlinburgh TN, a good 1,600 kms (one way) and mostly in stinking hot weather, my car did not boil over, but the temp gauge was consistently near the 100° mark.

I too have removed my fan and run a 10" electric fan, and I run with Water Wetter in the summer. That alone, lowers my temp by 10°.

Dave's comment about anti-freeze mix is critical. And, if you want a btl of Water Wetter, just give me a mailing address off-line, and I'll send you some.

You certainly might want to consider a 5-speed box, and 4.3 cwp, or better - both. Also you may want to consider an oil cooler. The adapters are available from Bob Grunau at www.grunau.garage@sympatico.ca.

Gord Clark
Rockburn, Qué.
Gordon A. Clark

Use "Water Wetter" or equivalent to improve the heat transfer.
and reduce the Antifreeze to at least 15% instead of 50-50. Then in cold weather increase it back to 50-50.

I use pure water and "Water Wetter" in the summer and get no higher than 85 C when expressway driving at 65 MPH for several hours with outside temp in the high 90's F ( or above 33 C).
This is from my TF temp gauge measuring temp at the exit of the water pump

Note I do have a 4.1 to 1 rear end and am crusing at 4000 RPM at 65 MPH or about 110 kph)

Water Wetter claims to reduce temp by at least 20 degrees F
Don Harmer

I'd like to see some pictures of the TF's with the electric fans. I too run at temps described above with the stock fan and the "Green Hornet's gonna be a little hotter soon. I will be putting on an oil cooler. I don't see me droping the 50/50 anti freeze mixture and I tried the water wetter and saw zero difference.

LaVerne
LaVerne

I thank you all, it is very interesting. I learned two things I did not think of:

- watch the mixture of antifreeze; I just put in some antifreeze without any idea of how much

- possibly change the radiator to a more efficient one; Carl Cederstrand of Orange has done that

- turn off the fan at high speed: I have not thought of that, I will try (extra switch)

- run at lower rpm's: I don't want to change the differential bridge, but I have an overdrive kit for TD's which I have described in issue 6 of Totally T-Type, http://www.tregister.org/ttt.aspx, p. 32

- I'd like to drink plenty of liquids before I "take off", but the liquids I am thinking of are illegal in large quantities!

La Verne, I am off to Louisiana - apparently not far away from you - and somewhat busy, but upon my return I will post a picture of the Kenlowe fan. I decided in favor if it when they started producing one with scooped blades, like spoons. I modified slightly its enclosure to make it fit the radiator exactly, passing over the different brackets etc. However, once I had it loose, and there was no difference. The advantage is that without the fan blades on the pump, the engine runs better. I would not go back.

Thanks again, Denis
Denis L. Baggi

A local mechanic surprised me by saying that tests show that the standard, large pitch four bladed fans move air than the plastic multi-bladed fans. He claims the plastic bladed fans were introduced because they are quieter, and lighter, and require less hp to drive, not because they are more effective at moving air. Has anyone seen any research or authoratative advice that supports or refutes that argument?
J H Crighton

The comments I've seen on the MGB plastic fans are more often related to failures of the original two piece " hand choppers". It appears that the heat issues that we see here are related to high speed/ high rpm engine load, in which case I would think it wouldn't make any diffence which fan was fitted as the car movment should provide sufficent air flow even without the fan.

Denis,

"Not far away" would depend on your prospective.
I would consider it a sizable distance.
New Orleans is about 1500 miles (2400 km) from me.

LaVerne
LaVerne

Denis, any chance that you're going to be in Southern California in early June? I'm heading out there from 5-12 June to greet a new granddaughter and thought that I'd try to get down to see our friend, Carl.
Bud Krueger

Such speed related high temps are characteristic of restricted exhaust systems, and any system resembling the OE one is in this category, even if undamaged. The thing was simply not designed to run at top rpm for extended periods. I've seen this on many different cars, for reasons ranging from poor OE design, to botched changes, to damaged systems, to mice in the silencers.
I don't know what the OE pipe size was, but generally all British cars of the time are overly restrictive for this sort of running - that's the big reason that modified systems were so popular and effective.
For an engine in this power range (60-100hp), the best first guess on pipe size is 1 3/4" OD, with a good silencer. At the lower end of the range, 1 5/8 (MGA size)is just passable, but not for extended high speed use. MGB used 1 3/4 OD pipes, and that is OK up to about 100hp. Silencers are a problem, unless you can see straight through them, and even then may not be as good as they might appear.
Since you are a numbers guy, I suggest you install a fitting in the downpipe and measure the backpressure at speed.

To give an idea of what you are looking for, I include the following from a study I've done on the subject; you may come up with a very useful power/fuel mileage improvement as well as solving your high rpm temperature trouble. You might well find that your existing system is giving backpressure readings considerable higher than 7"hg at your 5000rpm speeds.

Backpressure:
IS EVIL! It is also easy to measure and relatively easy and cheap to eliminate. Contrary to widespread folklore, there is essentially no known and documented case where reducing backpressure has any negative effects, provided that fueling and other tuning factors are adjusted to compensate for any changes.

Referring again to Vizard, a test was done on an experimental muffler, on a Mini 1275 GT, the successor to the Cooper S. This is a relatively highly developed power unit, so it is already better than many. Backpressure with the stock system was effectively a straight line between 2500 and 5000rpm, and increased from 2 to 7 in Hg, roughly 1 to 3.5 psi; the experimental one gave essentially a flat line at 0.5 in Hg, or 0.25 psi virtually the same as an open pipe. Comparing stock to experimental unit over this range gave power output improvement up 4 to 9%, torque up by 6 to 10%, specific fuel consumption down by 6 to 10%. There are some minor peaks and valleys, but practically these improvements are nearly linear. This is perfect validation of the basic function of engines: Power and all related measurements are directly proportional to airflow.

This experimental Mini 1275 muffler is the system now known as the RC40. It was later tested on a competition MGB with 130hp at the wheels and open exhaust, and caused a drop of only 4-5hp, with street legal sound levels. Since 130hp at the wheels is about equivalent to 160 flywheel hp, this 1- system is perfectly adequate for any engine producing less than say 130 flywheel hp or 100+ at the wheels. Even at the 160/130 levels it is far better than most stock or street legal systems.

Rover shows a drop of 10hp or about 8% gross to installed. The difference is mainly that the gross condition has no exhaust system past the collector. Thus, the pipes to the muffler and the muffler itself are the major source of the drop; the front portion of the pipe is either 2 or in some cases 2 , so no restriction there. The remainder of the pipes and mufflers are 1 , and must be the cause. There is no good reason for this other than cost and space requirements to get the required degree of silencing for a factory production car. It is clear from the Vizard info that this loss is unnecessary with the right silencer.

A further point on backpressure: Anything that increases airflow through the engine WILL increase backpressure, and the effect is generally non-linear. Once the system reaches its flow capacity, further increases will cause logarithmic backpressure increases. I therefore recommend that measurement ports be included in any exhaust system on any vehicle where modifications are proposed, and I recommend that BP measurements be taken and recorded before and after any mods, even such minor ones as air filter changes.

Any backpressure changes are certain to require fueling corrections, and it follows that any other mods that increase flow will require similar corrections.

If anybody actually does this test and subsequent changes, I would greatly appreciate getting a report on the numbers and results, by email direct.

FRM

FR Millmore

Denis, I had a two row radiator in my RHD TD that was never very efficient no matter what other changes I tried. Maybe it was not stock. I had the radiator changed to a three row (of vertical tubes) radiator and it made all the difference in the world.
Jim Merz

FRM and Gord.... thats interesting... I went to Gatlinburg as well and can comment on the temps...God, it was hot... no, hot doesn't describe it... the day before i got there I was on #81 and it was 100 degrees the whole day.
I was traveling at about 60 mph give or take...think I kept it about 3700 rpm or so... my temp was never above 90 C ... well, it may have hit 94 or so occasionally. My muffler is the resonator from a dodge Aries...it was the only one close to the original size and as a resonator is 'straight through'... had put it on when the original lost all its guts when we started the engine the first time (rust dust all over the floor behind the car)... anyway... the new one sounded the same as the old one... Wonder if the straight through design helps keep my temps down...have never been close to 100 C
gblawson (gordon)- TD#27667

I live in Florida and sometimes it is hot. I have had both TF-1250 and TF1500 along with several TD's. I drove one time from Rome Georgia to Florida when the temp ws 95 +. I ran at 4400 RPM most of the way on interstate 75. I have never had an overheating problem. This was with the stock radiator and original four blade fan. At that time I never used water wetter.Just anti-freeze at 50%.
Sandy
Sandy Sanders

I guess I'm a rare bird. But after almost 250,000 miles on my TF I still have the original and complete exhaust system. Mind you its covered with patches, but I always liked the original sound, so I've bent over backwards to keep the original one.

FRM:-the (1954) stock exhaust is 1½" ID. Its interesting to note that the fancy exhaust system being produced by Manley Ford is 1¾", or 36% larger.

You make a good point.

Gord Clark
Rockburn, Qué.
Gordon A. Clark

LaVerne: I meant, I would be closer than now. Re. the fan on the pulley and the MGB, my friend Carl Cederstand has fitted a third blade on the pulley so as to have six. I was going to do that, but then I opted for the Kenlowe, only for the saving in power.

To Jim Merz: I have had the same radiator since I bought the TD in 1965. I know it had a bad accident before my time, and it's possible the radiator is not original. But in that case, instead of reversing to the original one, I'd look for something more efficient such as, as suggested here, one in aluminium etc. Any source is welcome.

To Bud Krueger: I used to go often to Southern California, since the time of the swap meeting of the SCVMG Club - of which I am a member - coincided with academic meetings I had. I stayed at Carl's place more than once, the last time in his new house in Orange with its neat garage for his TD - which I was privileged to drive - and the Octagon on the floor at the entrance. But I have not seen him in years. Please if you visit him say hello to him and ask him to occasionally come back to this forum.

To conclude: I'll look at the radiator more closely, and possibly mount my overdrive. But in the meantime I have to fix the brakes, install Bob Jeffers' wonderful solid state regulator, and an invention by a guy in northern Switzerland, namely, a kind of non-protruding bottom cover which catches all oil drips and is almost invisible. I might publish something on TTT once I have it working. Plenty of things to do with those nice little cars.

Thanks to everybody, Denis
Denis L. Baggi

FR Millmore, Pennsylvania, USA, gofanu@usachoice.net

"The thing was simply not designed to run at top rpm for extended periods." I thought so.

Thanks for your interesting comment on backpressure. This raises a couple of questions to make sure I have understood: Where would I measure it? Exhaust manifold OK? Which values would you expect?

Yes, being fond of numbers and gauges I would love to add another one on my dashboard for backpressure. Currently I have: vacuum, water radiator - water head and oil temperature, standard oil pressure and ammeter, voltmeter, and a Tapley thanks to which I measure if the acceleration is correct - there is a hill which I normally cross at 550 lbs/t which corresponds to 2.4 m/s/s. I have space for an extra standard fuel gauge - connected to an electronic gadget in the design stage - an instrument showing the spark advance, and I have LEDs in the dash box to see the carburettors' temperature and the operation of both fuel pumps. So I am busy reading when I drive!

Thanks for the help, Denis

Denis L. Baggi

Would love to see a photo of your dash?
gblawson (gordon)- TD#27667

Yeah, Denis ... send us a pic of your dash - (with a map)!

Gord Clark
Rockburn, Qué.
Gordon A. Clark

I had no idea haw stupidly uninformed I am! I just get in and drive with the temp at 190 degrees.
Dick Thomas
TD13583
Dick Thomas

Dick,
190 F or C ???
Steve Wincze

I think Fletch may have hit it on the nose. I'm not so sure that a larger pipe is going to help as we're still going to have the bottle neck with the stock manifold that the majority of us have. I'm thinking that a crude zero to 60 test with the muffler in/out should give an idea of improvement. Thinking lower time should mean, increased hp, meaning lower back pressure. I can attest that my MGB with the Moss so called "big bore" stainless system with the single muffler has never run above the N mark ( whatever it means) even on 110 degree days stop and go or interstate speed. How many of us with the temp issues are running the Moss stainless system ? I sure going to adress the flow issue myself as I'm planning on cramming a lot more in from the intake side and it won't be good if it's not getting out down stream.

LaVerne
LED DOWNEY

Will make a photo of the dash, but I was waiting to have nore instruments installed! Never mind.
Denis L. Baggi

OK, here is part of the dashboard, except for the voltmeter at the far left outside of the field of vision, and the LEDs in the glove box for carburettor temperature and fuel pump spies.

From the right you see: Tapley accelerometer (1936?); vacuum gauge (connected to the inlet manifold); water temperature at the head, oil temperature at the sump, and between those two: one LED for the alarm, one LED for the Kenlowe (the two dots between tachometer and speedometer); water temperature at the radiator; then the standard oil pressure and ammeter. Clock is out to England.

As you can see, there is plenty of place for other instruments!

Thanks to all, Denis

P.S. My wife's Cherokee is illegally parking at the place of my 2004 MG TF!


Denis L. Baggi

Steve-

C of course!

Dick
Dick Thomas

Denis, if the rest of your car looks as well kept as the instrument panel, it must be beautiful. How about some more pictures?
Jim Merz

OK, a few points:
There is nothing wrong with the engine running at or near 100C, and it has much to recommend it. I wouldn't want any engine running below about 90C, as it is nasty on oil contamination, etc. 70C is certainly too cold. The ideal is near 100C CONTROLLED BY THE TSTAT.

Dennis is showing us that his temp is being driven up at high rpm by the simple operation of the engine, and that is where the exhaust restriction shows up. The operative words are "5000rpm" and "That behavior has almost nothing to do with outside temperature." This means that the situation is caused internally, not by high ambients, and probably not by simple external engine loads (the car).

I would remove the mechanical fan completely for operation at high speed - it moves air very inefficiently at these speeds, makes a lot of noise out of a significant amount of power, and functions as a radiator block to airflow. (I think Dennis has only the electric?) The electric fan should keep the thing cool at low speeds. There is absolutely NO advantage to having the electric fan switch on before the thermostat opens; all you accomplish is blowing air through a cold radiator. Fans should come on 5-10C above the tstat temp. If the stat is at 95C, set the fan at 100C; if that makes you nervous, use a higher pressure cap to allow safe operation to 110 or more. Forgot about TD not having pressure - might be a good idea to figure out how to fit one with an expansion tank! Non pressure systems run at 90 w/ fan on at 95.

Note that pressure on the system will also reduce or eliminate cavitation. I would guess that cavitation is a significant problem at 5000; a big pulley might be a good idea. Since the system is primarily a thermosyphon by design, low speed cooling should not suffer..

The backpressure measurement fitting should be in the front pipe, a few inches past the manifold connection.

Backpressures may be as high as 20"hg/10psi for a really crappy silencer, or as low as 0.5"hg/0.25psi for a really good one. I would say that 4"hg/2psi at max rpm is the upper acceptable limit, but there is no excuse to settle for more than 2"hg/1psi at your normal max cruise; any more is costing you power and fuel.

Given these numbers, you will want to start out with a decent fuel pressure gauge or similar, and progress to a manometer for lower pressures.

LaVerne's worry about "manifold restriction" is unfounded. The stock T series manifold is arguably too big and too short to help power much, but it's not hurting any by way of restriction. You will not necessarily see any improvement by just removing the muffler, since fueling/timing corrections may be needed, but if there IS a noticeable improvement, then you can be certain the system is very restrictive.

Gordon, is the system 1 5/8 OD/ 1 1/2ID all the way back?

Silencers are almost always the worst part by far. It is well worth getting Vizard's A series book for the exhaust info alone - at today's fuel prices, it can pay for itself really quickly. His pictures of the abominable stuff done even in "reputable aftermarket performance" silencers is appalling. It is very common that identical appearing mufflers have differing flow capacities by a factor of two or more.

I once had an Austin America to Cooper S spec, with a homemade 1 3/4OD system, single 36" straight through silencer. That car died, and I got another. The stock 1 1/4OD system fell off, and I needed to fix it fast. Since the big system needed floor mods that I had no time for, I made an adaptor to fit the big pipe & silencer from the gearbox back. So, I had the stock engine & manifolds, with about 3feet of 1 1/4 pipe, going up to 1 3/4 through the big muffler. I left home and forgot about the change until I got out on the highway and stood on the gas - the thing actually frightened me with the acceleration above about 3500rpm. This also gained me several mpg at highway speeds. There is a characteristic "whooshing" sound that the 1100/1300 cars, Magnettes and others make that is the direct result of extremely restrictive silencers; this goes away with a decent system.

Enough for now!
FRM
FR Millmore

Thank FRM. To which I take the liberty of adding:

- running temperatures do not stay at 70, but after say half an hour everything is somewhere over 80C, which I think is reasonable. It is around that time that the car runs in the smoothest possible way

- I only have the electric fan, but it comes in only after the thermostat opens. It's a lot of fun to watch the temperature at the head rise while both radiator and oil needles don't move. Then, when the stat opens, radiator temperature rises rather quickly, and when it goes over 70V then the fan comes in. And somewhat later, oil temperature starts rising

- the cooling system is not pressurized but I have an expansion talk sitting at the battery bracket. When the temperature rises, water flows up to the tank, and when it cools, water goes back to the radiator, since the tank is higher than the radiator top. By "not pressurized" I mean that the expansion tank has two compartment, the second is for overfill in which excess water spills over and leaves through an overflow pipe, hence everything is at ambiance pressure

- the idea of measuring back pressure is very appealing, do you think an instrument like the one used for intake vacuum would work? It has an end-scale value of 30 Hg.

- I have not thought of switching off the fan when I go very fast. Incidentally, 140 kph is fun and scares the hell out of a passenger!

I don't have many pictures of my beloved TD, but here is one, rather old and not that sharp, but I like it because you do not see me too well!

Denis


Denis L. Baggi

This thread was discussed between 09/05/2008 and 11/05/2008

MG TD TF 1500 index

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