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MG TD TF 1500 - Cooling Systems Problems? - Possible Solutions

This forum has been a great help to me in that past and I would like to contribute the following article.

Cooling Systems Problems? - Possible Solutions
MG “T” Series, MGAs and early MGBs

MGs in general are notorious for having cooling system problems. The original design was, at best, marginal, even for the cooler climates of the United Kingdom. These cars when driven in the southern third of America or in modern day traffic, anywhere, will likely experience overheating problems. So, what can be done to improve the overall cooling efficiency of the system? Before you begin to make improvements you must first verify that car’s radiator is clean, the hoses are leak free, the fan belt is tight, all ensuring that the stock cooling system is operating at maximum efficiency. Additionally, be sure that the timing and carburetor air/fuel ratio are set correctly as these too, will influence engine-operating temperatures. The improvements that can be made are as follows:

1. The most effective, but most costly, modification is to re-core the radiator with a modern high-efficiency 3-row tube design core replacing the stock two-row design. This greatly improves heat transfer and will, in itself, likely solve your overheating problems. Most radiator shops can re-core the “T” Series radiators. The downside is that it will require the removal of the radiator and will cost upwards of $400.
2. If your car’s only problem is overheating when operating in slow or in bumper–to-bumper traffic but otherwise okay, then a replacement fan may solve your problem. My understanding is that the 7-blade plastic fan (Moss p/n 434-340 - $76.46 at LBC) that is used on later model MGBs will fit the “T” Series cars. I do not have any personal experience with this fan, but it appears to be a sound approach to solving this specific problem.
3. The most cost-effective modification that you can make is to convert the current “open-to-atmosphere” cooling system to a pressurized coolant recovery system. Please see Building a Pressurized Coolant Recovery System” below. Water boils at 212 deg. F or 100 deg. C (Higher, with antifreeze added, but for the purpose of this paper, we will assume that water and the water/antifreeze mix coolant boils at the same temperature).

If, under all normally encountered driving conditions, your car operates at less than 212-degrees F, the open system is just fine. However, if on occasion, you exceed 212 degrees by even a small amount, the coolant in your radiator will boil, the steam generated will vent to atmosphere and when the engine cools it will contain less coolant and, hence, less cooling capacity. As this cycle is repeated, boiling will occur earlier in the cycle and with a greater coolant loss. If you do not top-up your radiator at frequent intervals, overheating will surely occur.

In an even worst scenario, assume that your cooling system is marginal for your car’s typical operating conditions. On a very hot day, you are driving on the freeway at 70 MPH and the coolant temperature increases to 212 degrees. The coolant will begin to boil, and steam will be created. Steam, being a poor heat transfer medium will exacerbate the cooling problem and, to make matters worse, the steam generated will be vented, resulting in less available coolant and a lower radiator cooling capacity. If the car is operated in this high speed, high ambient temperature, steady state condition, engine-operating temperatures will continuously increase and continuous coolant loss will occur. Unless you notice that the car is overheating and pull over to let that engine cool you will shortly exceed the critical temperature and the engine will seize. A very costly repair!!!

How can a pressurized coolant recovery system help? This type of system, in use since the 1960s, performs two functions. First, it pressurizes the system and second it allows for coolant that would normally be lost to be recovered. By pressurizing the system, to say 7-PSI to13-PSI (typical radiator cap ratings) above atmospheric pressure, the water’s boiling point will be increased to between 233 deg F to 246 deg. F. Additionally, when starting a cold engine and as it warms and reaches its normal operating temperature, the coolant in the radiator will expand. The expanded coolant will create positive pressure in the radiator and open the radiator cap’s bypass valve and coolant will flow into the car’s radiator coolant expansion tank (aka - radiator overflow tank). Later, when the engine is shut down and allowed to cools, a strong vacuum will develop in the radiator that will open the secondary bypass valve in the radiator cap. This permits coolant to be sucked back into the radiator, thus replenishing the coolant level. This cycle is repeated trip after trip.

With occasional minor overheating, the increased boiling point of the coolant will eliminate the generation of steam and, hence, minimize permanent coolant loss. The result is less frequent radiator top-ups and the reduced probability of future overheating problems.

If a temporary problem is present or if ambient temperatures are extremely high (e.g. a worst case scenario), the pressurized system will allow the engine to operate and an elevated temperature above the coolant’s normal boiling point. If the engine can reach an equilibrium temperature of 220 deg F or less, the engine will operate without catastrophic damage. Ideally, an engine should operate in a temperature range of 180 to 200 degrees. The occasional operation of up to 220 degrees is not desirable, but a far better alternative to overheating and an engine seize up.

4. To help detect a real-time overheating situation, you should consider adding a visual and/or audible alarm system. On my TD, the radiator has a 3/8-inch NPT (tapered) female fitting installed on the engine side or the radiator. I used this fitting and installed a temperature sensor normally used operate a modern-day temperature controlled, electric cooling fan. The sensor has an internal switch that closes at 204 deg. F. The sensor is wired to a dash light and a mutable alarm. If I am not attentive to the temperature gauge, the high-pitched alarm will certainly correct that situation. There are, of course, other ways to accomplish this idea. The objective is to install a sensor/switch in the cooling system and wire it to at, least, an audible alarm.

The temperature sensor switch that I used is NAPA P/N FS116 - $34.99. This switch has a 3/8-inch straight thread. It works, but you will be better off if you can find a switch with a tapered pipe thread. The mutable piezo alarm that I used was purchased from www.floydbell.com , P/N OC09-530-QO – $28.42.

(PS – I installed one of these alarms in parallel with the low fuel level warning light. I now have an audible and visual warning when the fuel level is low)

5. One last suggestion; there is a product called Water Wetter, made by Redline and available at Advanced Auto, Amazon.com and other places. The manufacturer claims that, when added to your radiator, your car will run up to 30 degrees F cooler. I don’t believe 30 degrees, but online testimonials claim actual cooler temperatures. It is most effective when used with water only (e.g. no antifreeze). It is supposed to contain anti corrosive and water pump lubrication agents. I have no personal experience with Water Wetter, but for under $10.00, it may be worth a try.



Building a Pressurized Coolant Recovery System

The design objective is to construct a small sealed chamber that can be pressurized by the stock cooling system. This pressurized chamber will act, in many ways, like a miniature radiator. Also included is a radiator coolant expansion tank that will store the overflow coolant.

The items required are as follows:

1. Two 2-inch copper plumbing end caps.
2. 3-inch section of 2-inch copper pipe. (Items 1 and 2 are used to make the pressurized chamber and can be purchased at a commercial plumbing supply house.)
3. Standard, small or large size, new or used brass filler-neck for a copper/brass radiator.
4. Mounting bracket made from a 1”x3” strip of brass or steel sheet metal with screw mounting holes drilled about 1/4-inch from each end.
5. 7-PSI to13-psi radiator cap, sized to fit the neck.
6. New or used small size coolant expansion tank. (A junk yard is a good source)
7. 2-inch length of 5/16”-copper tubing.
8. Two lengths of 5/16”-rubber fuel line (length to fit) and 4-hose clamps and a length of rubber tubing for the expansion tank’s outlet to atmosphere


To construct…

1. Drill a hole, with a size that matches the diameter of the radiator’s brass filler-neck (item3) in the flat end of one of the 2-inch copper end caps. (A spade-type wood boring drill bit will work)
2. Place the end caps over the copper pipe and solder together.
3. Drill a 5/16” hole in the side of the end cap without the hole for the radiator neck, about a ½-inch from the end. (This assumes that you will be mounting the chamber upright. If you are going to mount the chamber on its side, drill the hole in the bottom of the end cap)
4. Insert the 5/16-copper tubing (item 7) in the hole about half way and solder in place.
5. If mounting upright, solder the sheet metal mounting bracket (item 4) to the bottom of the chamber and centered on the end cap.
6. Insert the radiator neck (item 3) through the hole in the top end cap and solder in place.

The pressure chamber is now complete.

Assemble as follows:

1. Mount the pressure chamber at a convenient place in the engine compartment. I mounted mine on the topside of the passenger side frame rail.
2. Mount the expansion tank in an inconspicuous spot. On the front and right side of the toolbox, the backside of the frame cross member, just below the radiator are good places.
3. Using an appropriate length of rubber fuel line, connect the end of the radiator’s stock 5/16” overflow pipe to the 5/16” copper tubing installed in step 4 above. Secure in place with hose clamps.
4. Connect the Expansion tank to the 5/16-inch inlet/outlet pipe on the radiator neck (item 3 above) using the appropriate length of fuel line and secure with hose clamps.
5. Fill the expansion tank to the cool level mark. Fill the radiator to the bottom of the filler neck. Screw the original chrome radiator cap onto the radiator and the new 7-PSI or 13-psi radiator cap onto the copper pressure chamber.


You’re Done!!! Happy Motoring!!!

PS – If you have any questions, please call me at 843-838-0822 – Frank Grimaldi
Frank Grimaldi

See the comments on the MGB Technical BBS for a different view of this subject. Cheers - Dave
David DuBois

It is possible to have an overflow tank to which water moves up when the engine is hot and moves back when it's cold without pressurizing anything. An you may just use the existing overflow pump at the r.h.s. of the radiator, as I have done.

Denis
Denis L. Baggi

"It is possible to have an overflow tank to which water moves up when the engine is hot and moves back when it's cold without pressurizing anything"

That is what I did also and find that it works fine. Pressurizing the system may be beneficial for people living in very hot climates. Cheers - Dave
David DuBois

Frank Grimaldi wrote:

The temperature sensor switch that I used is NAPA P/N FS116 - $34.99. This switch has a 3/8-inch straight thread. It works, but you will be better off if you can find a switch with a tapered pipe thread.



I also want to use such a sensor. With the part # NAPA throw out M16x1,5mm but Frank mentioned 3/8-inch.

What is right? Did NAPA changed?



W. Mueller

Or is this the right one?

W. Mueller

Hi Frank. I'm not sure the statement "The original design was, at best, marginal, even for the cooler climates of the United Kingdom" is entirely accurate. Many, if not all of the problems attributed to the poor cooling design can be traced back to a lack of maintenance. If the block is cleared of the rusted gunk that will have accumulated over the years, the radiator re-cored (or at the very least least tested for leaks, flushed & cleaned) & with the thermostat & water pump in good condition & operating as they should, the original cooling system actually performs really well, even in hot climates like Australia. I'm sure your proposals would make the XPAG run a little cooler but so would a well maintained & clean system. Cheers
Peter TD 5801
P Hehir

Frank,
A coolant tecovert tank will not help the rinning hot condition. All the recovery sys does id prevent the coolant from going to the ground.
Once the engine reached the hot level the coolant is in the recovery tank, it is not helping to cool the system. Pressurizing DOEShelp in cooling.
Steve
Steve Wincze

Steve, how does pressurizing the system help in cooling?

As I've understood, pressurizing the coolant came about to allow the water temperature to get above boiling (to allow the engine to run hotter) to assist in the more efficient burning of gasoline and to recapture boiled-off water (closed system).

FWIW, I'm running an unrestored, unaltered car and am hitting 85 to 90C on hot North Carolina days. If properly maintained and tuned, there shouldn't be too much of a problem - unless you're driving in Arizona at 100+F.

..
MAndrus

I think that anyone with a 60 year old car having cooling problems needs to check for the #1 problem first, because if you don't solve that, everything else is merely a bandaid. I'm referring to making sure that the water passages in your engine are not blocked with junk. Mine was, and it is very common on these old engines. Flushing the system won't clear it. In fact, when I had the block boiled, I was still finding stuff using a variety of wires and sticks and long brushes. I had it boiled twice and went over every hole in the water passages by hand repeatedly until I was sure it was clean. THEN I drilled the extra hole as per thread instructions in the archive which allows more water to flow to the core of the engine.

http://www.ttalk.info/XPAG_Cooling_System.htm

http://www2.mg-cars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=8&subjectar=8&thread=2009092203351913738

If you don't do this, you're never going to be sure what the condition of your block is... until something happens, as it did with mine. So little water circulated through the blocked passages that the middle cam bearing overheated and partially melted. Luckily it was at low speeds and low revs so the engine just stalled, rather than causing more catastrophic damage.

ONCE you've made sure you have a spanking clean block, you can then proceed with confidence to repair or improve other parts of the cooling system, including the radiator, water pump, etc. But then again, you may find, after cleaning your block, that you don't need to!
Geoffrey M Baker

I think what Herr Mueller is looking for in this 7 year old thread is a part number for a temperature triggered alarm switch. The article says the radiator threads are tapered (makes sense) but the NAPA transducer(?) apparently has parallel threads. I can't answer his question but I think we all agree that a clean block and free flowing radiator helps cooling. Jud
J. K. Chapin

Thank you Jud for the support!

It is not only a question of tapered or not. It is also a question of the thread size.
W. Mueller

I applaud the efforts of the original poster, but like Peter I disagree with the article. There is nothing wrong with the T-Series cooling system IF it is in proper condition and the engine tuned correctly. "Proper" being as it was when new. With 1250cc and a radiator larger than the engine itself, there is no reason why a TC/TD should overheat. Modified engines are another matter of course, but I feel there is plenty of overhead.
Steve Simmons

I live in Tucson and have read many, many threads about overheating in these temperatures. As I am getting back a rebuilt engine (hopefully today) with cleaned water passages, and am installing a cleaned and rodded radiator, along with a new Moss water pump, I look forward to finding out how a near-factory original system actually performs! I have performed a few mods including drilling out the front block hole as mentioned in other threads, and grinding out some of the worst casting obstructions in both the inlet and egress areas of the water jacket.
I hope to install and test and then compare temperatures with both a standard 4 vane and a improved 6 vane impeller as well.
My only issue is I would really like to move the water temperature sender from the radiator top (where it mostly just measures the temperature of the radiator steam) to the block itself, for more accurate measurement.
Geoffrey M Baker

Mandrus,
You are absolutely correct, presurizing will not help to lower the temp in the system, it just allows it to get to a higher temp before it boils ...
Steve
Steve Wincze

Why are we resurrecting 7 year old threads? Just to rehash them? Bud
Bud Krueger

@ all

I just wanted to dissolve the contradiction between the NAPA part and the statement of Frank on the thread. My vehicle is away at the moment and I would like to order the switch.
W. Mueller

Bud,
I didn't realize it was a repost!!
Maybe any reposted thread should show in red text

Steve Wincze

Herr Mueller, check with NAPA:
http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Coolant-Fan-Switch/_/R-ECHFS116_0372797271

They say M16x1.5"

Bud
Bud Krueger

Hi Bud,

but Frank Grimaldi wrote:

The temperature sensor switch that I used is NAPA P/N FS116 - $34.99. This switch has a 3/8-inch straight thread. It works, but you will be better off if you can find a switch with a tapered pipe thread.

That is the contradiction.
W. Mueller

All I can show you is what Echlin put on their data sheet
Bud


Bud Krueger

Just wondering... is the bung soldered or brazed on? If so, it'd be pretty simple to install one to suit your sensor. The long way around I know, but possible.

.....
MAndrus

Herr Mueller,

Not sure where you're going to install the switch but if it's in the radiator outlet I do believe it's threaded 3/8" NPT. Try googling 3/8" NPT temperature switch to find one that will work. Here's one which

"When the coolant reaches 185°-215°, the contacts on the cooling fan switch close, activating a relay which directs current to your electric fan. When the engine cools, the contacts on the fan relay switch open, and the fan stops automatically."

http://www.speedwaymotors.com/Electric-Fan-Sensor-3-8-NPT,37703.html

I'm sure you'll find a number that will work for you.

Gene
Gene Gillam

That's obviously not a tapered thread. Note the washer.
Bud
Bud Krueger

Maybe I'm just lucky but I tend to agree with Steve Simmons. I find the entirely stock radiator and water pump quite adequate for the car even in 95 degree weather. Now admittedly, in deference to its age, I do not drive my car at anything near to the 70 MPH mentioned in one of the posts. I have other British cars, a Jaguar 3.8S and Austin 1300 that do have marginal cooling systems but also have Morris Minors that are equipped with very good cooling systems.
John Quilter (TD8986)

I have several pre-war cars and I count my TF as a pre-WWII car from a design standpoint. At this altitude and with the hills we have, the temperature gauges also serve as a grade indicator. The cars are in solid condition, but the cooling systems had very little design margin, near as I can tell. The best one I have a Ford Model A. It does not overheat easily. So far the TF has been pretty good, too, but I do not drive it above 55 mph.
MW Davis

Hey, you need to remove that IFS, pressurized cooling, fancy headlamps and wide radial tires if you want to be pre-war! ;) You ain't felt nothing until you drive 300+ miles straight on solid axles and 3" rims.

The TF cooling is definitely a step behind TA/B/C/D with the smaller radiator and grill slats, but at least it's pressurized to help when things do get hot. And the MGA got it even worse. Very poor airflow.
Steve Simmons

Gene Gillam wrote

Herr Mueller,

Not sure where you're going to install the switch but if it's in the radiator outlet I do believe it's threaded 3/8" NPT.

Thanks Gene,

yes I want to use the radiator outlet for a quick solution.

I also believe there are only a few or none metric threads and so it should be 3/8". I guess NAPA has changed the articel since Frank had ordered.

I'll purchase this one here in D.


W. Mueller

Edit:

Switch is also: DAIHATSU 83430-87102-000
in Europe Applause I and Charade III
W. Mueller

I cannot imagine that the thread on the rad is NPT. I would think it is 3/8" BSP the same as on the fuel tank. I mentioned this to W. Müller already on the German website.
Regards
Declan
D Burns

Declan,
I would say NPT. On the TF there are 2 tappings on the thermostat housing one is BSP for the heater outlet and the other is NPT for the temperature bulb. Woe betide you if you mix them up!
I have been both a marine and hospital engineer and find that most bulb type temp gauges fit NTP on British equipment. Caused many problems on multiple tappings. Normally the NTP tappings for bulbs are parallel tapped while the BSP are taper.
Ray TF 2884
Ray Lee

Ray,
You could be very well right about the thread on the bulb. Here's a photo of mine and it could be that that is an adapter from NPT on the bulb to BSP on the rad. I have never had it out to check.

Regards
Declan

D Burns

Thanks for the input re the NPT thread. I can confirm that the heater connection is BSP on my 1955 mgtf 1500. I tried both BSP and BSPT plugs in the temperature bulb fitting between engine and thermostat and they would not engage. I guess as I want to keep the TF as original I only think BSW, BSF, BSP & BSPT

I will try a NPT plug next week as I want to send off my instruments for repair and continue to drive the TF during the repair period. I will let y'all know if it fits
I Massey

We should think ourselves lucky that MG didn't throw in some British Standard brass or British Standard Cycle threads.
I have some British motorcycles and every one has a different thread system, but at least my Whit spanners fit them all.
Also lucky I served my apprenticeship with a European/International company so I still have my pre ISO metric taps and dies (metric fine) for the TF.
Ray TF 2884
Ray Lee

Ray,
They did!
Take a look at the TD gearbox speedo drive-that's exactly what you are referring to -it's British Standard Brass. I have the taps and dies for it.
Regards
Declan

D Burns

Declan,
I am surprised that any of our cars have stayed together as long as they have.
What are the bets that there is a BSCyc thread somewhere!
Ray
Ray Lee

The four studs on the windscreen swivel system are 5/16" x 26tpi, which is a BSC, or cycle, thread.
R A WILSON

Ray,
That's one I wouldn't bet on-you are probably right.

Declan
D Burns

This thread could go on forever.
All brass threads are 26TPI because all brass pipe used to have the same wall thickness.
So, windscreen studs could be either, I will plump for BSCyc so we have one of every British screw thread in use at the time, including the BSW on the dynamo adjuster!
Ray
Ray Lee

This esoteric info needs to be collated & included in the existing lists of what thread goes where. Maybe some additions here for you Chris? Cheers
Peter TD 5801
P Hehir

Posters are talking about coolant fan control switch threaded into a boss in the radiator or elsewhere. That may not be necessary. My 1965 Jaguar 3.8S has a retrofitted Hayden electric pusher fan which is controlled by a thermostatic switch that for all the world looks like a large nail with wires attached. It simply pushes into the radiator between the fins and tubes. This has worked quite well for many years and is further controlled by a potentiometer that is adjustable. I believe this item came. or was optional, with the Hayden fan I bought and fitted to the car.
John Quilter (TD8986)

A little bit late but I want to tell how the story ends.

I'd used a 3/8 coupling nut and a thermo switch with 3/8 gas thread (tapered).



Bela

This thread was discussed between 26/05/2008 and 16/04/2016

MG TD TF 1500 index

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