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MG MGB Technical - Infamous Summer cooling issue

I have a 1964 MGB 3-main with the original engine, 64,000 miles total. I am the third owner, and have it 3/4 restored from its 20 year hibernation. With just some tinkering the motor now runs great. I live in Minnesota. When the outside temps are cool, the motor runs cool enough. But when it is 90-95 deg F outside, it tries to run hot on the freeway especially… the gauge one time got to approx. 218 deg F on the freeway. It never spits out much coolant from the radiator though. But it seems to not go past 205 deg F when its only 60-70 deg F out. And I haven’t continued to run it in the hot weather lately because I don’t want to trash an otherwise good engine. I have verified the gauge with an infared thermometer and a stem thermometer. If the gauge is wrong, it’s not reading more than 5-8 degrees on the high side. Here’s what I know: the engine has always run hot, my father the second owner said, with Su’s too. Now it has a new radiator, flushed out standard oil cooler, newer water pump, downdraft Weber with performance jets. The engine compression is great. I did a vacuum check too and it also showed the engine is in great shape—the head gasket is not blown. Valve clearances properly adjusted. I run 93 octane fuel. The spark plugs are not overly white (overheating) but their color and condition seems to indicate its running quite hot. I’ve adjusted the timing all different directions and it doesn’t make any difference regarding cooling, but I think I’ll try again anyway. I’ve flushed the engine, flushed the cooling system, and tried all types of thermostats including a blank… still running warm with a gutted thermostat installed. 7psi cap. Wetter doesn’t help either. I have the heater shut off, although it ran warm with it open in the summer. But I really want the car to not overheat just because I shut off the heater to avoid a blistering hot cockpit. So assuming my timing adjustments do not help still, I am thinking the cooling system is just insufficient for the car at highway speeds in hot outside temps. Does anyone have any other possible solutions? Or potential problem areas to check? If not, should I install a radiator with more rows? (or JC Whitney sells a auxiliary radiator I guess you add on to your existing radiator). An electric fan rather than the 3 blade? Or a larger oil cooler? All suggestions welcome. Thanks, Chad
Chad Westom

Chad - Important question #1 - where did you get the new radiator? Important question #2 - does it have the original, 4 row L type core in it (this would be a core that looks exactly the same as the original core). If the answer to question 1 is Moss and the answer to question 2 is no, then htat is your problem. Most, if not all aftermarket radiators will not cool the MGB properly. Conversely the proper radiator and an engine with clean cooling passages will have no problem (see my comments in the thread regarding New Radiator). In that thread, I gave a web site for Modine which supplies the proper core for your radiator. With that in hand, find a good radiator shop and see if they will order a 4 row L type core and put it in your radiator. If you can't get someone to do this for you, let me know and I will give you the address of a shop here in Bremerton that will do it. The next problem is the engine. If it has had a long term problem and has never been rebuilt, it may have clogged up cooling passages that the simple flush that is available to the consurme cannot get out. The ultimate answer may be a disassembled engine in a hot tank and or acid dip. Good luck - Dave
David DuBois

Chad - The other thread I refered to is "New radiators from Moss". There is a web site quoted in there http://www.radiator.com that has, what looks like the proper radiator, but you would have to check with them as to whether or not it has the proper core in it. If it doesn't, then don't order it even though is would save money, because you would be in the same situation. Dave
David DuBois

Thank you Dave. I'll research the radiator issue. Any idea on what the maximum coolant temp should be on an early B? 190 deg F? 205 deg F? 210 deg F?
Chad

Boy, does this sound familiar! I've just finished restoring my '64 and have the same issue. I did buy my radiator from Moss, so I'll research the other radiator and see if it helps.

Thanks,
Rich

http://64mgb.home.mchsi.com/
Rich F

Chad,

One additional cause for running hot, per the Haynes manual, is air / fuel mixture is too lean.

Good luck!
Greg
Greg Knodel

Chad - I am running a 190 degree thermostat in my 67 MGB and it runs consistantly at 195 degrees. The highest it has gotten is 205 - 210 when I was going over the Grapevine in Southern California in hot weather (this is a streatch of I5 with a long steap climb that has the road side littered with overheated cars like discarded bear cans). Some have asked me why I am not using a 180 degree themostat. The simple answer is that the car seems to run better at the higher temperature. The 180 degree thermostat will not make the car run any cooler except in very cool weather, the thermostat only sets the minimum operating temperature of the system.

One additional item that will help (not cure your problem) close off the gap at the top of the radiator and the diaphragm. Also make sure that the sealing strip is in place at the top of the diaphragm. This will force all the air through the radiator rather taan alolowing some of it to flow around (or over) it.

Another question for you Chad, what mixture of anti freeze are you using? Montana is one of the few places that I could see needing even a 50% solution. If you are running more than a 50% solution, you are seriously degrading the coolant's ability to transfer heat. Even with a 50% solution, it is degraded 25 % from pure water. Don't take this as a recommendation to run plain water, you need at least 25% - 30% antifreeze for the corrosion protection.

Finally, Greg's point about running too lean is worth looking into, along with draging brakes
Good luck - Dave
David DuBois

Dave,
I don't know if you have tried this before or not, but Prestone does offer a combination Anti-corrosion inhibitor/water pump lube package that I have used for many years now when running a solution of deionized water and Redline Water Wetter to assist cooling. In checking out the water passages in the block, head, and radiator over those years, the amount of corrosion has been very minimal. Some, like my radiator repairman, would say it "looked pretty darn clean for an old radiator" when I had a seam leak fixed a couple years ago.

I mention it as it seems to have done as good a job for me as the additive package in a good quality antifreeze. FWIW.
Bob Muenchausen

Hi,
I have the same problem with my 1980 MGB runs hot in traffic or in town at low speeds but OK on the highway. The electric fan works but it seems that more air flow is needed through the Rad . Does the electric fan draw the air through the rad or push it out through the front. It will also cool down when ideling.
The timing is per manual.

Cec Fry
Cec FRy

Before spending any money - check the temp guage is telling you the truth - mine runs about 10 degrees F higher than the true temp in the engine..........
Chris Betson

There have been reports of the wrong water pump physically fitting but not pumping enough water. If the rad outlet is cool when the engine temp is high then flow would seem to be the problem rather than the ability of the rad to get rid of heat.
Paul Hunt

Chad-
If the engine is running cool enough at low speeds but hot on the highway, the first thing to check is the coolant intake hose that runs from the bottom of the radiator to the coolant pump. At the higher sustained RPM you're running on the highway the coolant pump is sucking more coolant, so a flimsy hose can partially collapse and restrict the coolant flow. With the engine cold, reach down there and give it a squeeze. It should have very little compressability to it.
Steve S.

I had a similar problem with my 79 B. I tried a lot of suggestions mentioned in this thread. Finally a friend told me to pull the electric fan back about 2inches and build a shroud around it. Once I did this all my cooling problems went away.
Bob

Chad --
I've got a 66B (with the 3-blade metal fan), with the same problem. (See my earlier post.) My old, original radiator did a good job. The car ran at a steadfast 190°, which is what John Twist, anyway, recommends as optimum running temp.

I bent a fan blade on a new plastic radiator shroud, and tore a hole in the old radiator. I replaced it with a new radiator from Moss, which just is not doing the same job. (Nothing else has changed.)

It now runs above 212° when climbing a hill, which it never did before.
Also climbed up to about 220° during a long idle in traffic, and this was on a pleasant 75° day.

Moss is taking the radiator back, and I'm having my old one recored. The new radiators are all made in China, and apparently are only 3-row cores. The old one will be recored with a 4-row.

The other option for early B owners is adding an electric fan in front of the radiator, to push air through it as needed. I'm thinking about getting one. They have thermostats on them, and go on when needed. Or, I like the idea of having a switch for it hidden under the dash, so I can turn it on just when the temp starts to climb.
Kim de Bourbon

I can confirm the efficiency of the electric fan at the front of the radiator...I've got one fitted to my 69B and it's kept the engine cool through the hottest of Australian summers, for many years (it also has the original radiator).

mike donaldson

Chad,
All things above seem like excellent suggestions but there are a couple things trivial things that might help. It seems that the later 7 blade plastic fan is regarded as being the most efficient mechanical fan for our cars, this might help if fitted in conjunction with a well fitting shroud. Another thing to look at is wether or not the fan is fitted backward or not. I don't recall seeing an early 3 blade metal fan lately but like the other fans I believe it has slightly curved blades. If the curve is facing the wrong way it will not pull as much air as it could otherwise. And when you changed water pumps, just because you put it back on the way it came off doesn't mean that somebody else didn't but it on wrong 30 years ago
Jared Snider

Bob - With the additive package, do you use any anti- freeze in your cars at all? I can't imagine not having anti-freeze in a car in the winter in Boise.

All - When fans (either 3 or 7 blade or electric) are donsidered, one thing needs to be kept in mind. If you are driving at over about 20 MPH, there is more air being pushed through the radiator than any fan will pull or push through it. So for those who are overheating at freeway speed, a new fan (even if it has 20 blades) is not going to help. On the other hand, those who are having a problem at idle, when stuck in traffic, the fan might be a contributing factor. Regarding the curvature of the fan blade, to me it is counter intuative in the direction it is curved. Look at the angle of the blade and picture if it is pulling the air through the radiator when it is rotating clockwise. In other words, standing in front of the car and looking at the fan, the right side of the blades should be forward of the of the left side. Good luck - Dave
David DuBois

On the metal 3-blade fans on the early cars, there is a "notch" on the lower edge of one side of the blades. The notch should be on the leading edge.

(Someone else just gave me this tip to check on my car, in case the blades had been put back incorrectly. This is something he learned from John Twist at the recent NAMGBR show in Dallas.)
Kim de Bourbon

Dave,

I switch seasonally between a 50-50 antifreeze/dionized water solution in winter, and the above mentioned concoction in the summers. Both work very well in their respective seasons.

Kim,

I have put an electric Pusher fan in front of my radiator and have had very good luck with mine, even in our well over 100 degree weather here recently. A puller would be better, but our car's (mine's a 68 GT) radiator positions preclude that choice. One thing I have learned tho, when you mount it, try to center it in about the same position as the OE mechanical fan in relation to the radiator. Too far to the left of right does not work as well for some reason. I had a temp sensor switch threaded collar from a Toyota soldered to the top tank just right of center and use that switch to control the fan via a relay.
Good Luck!
Bob Muenchausen

With the engine off and cold you will be able to squash the bottom hose flat just like you can the top, less so when it is at running temp and pressure. What offers the greater resistance to water flow - the radiator or the engine? I keep reading about this bottom hose getting sucked flat but just can't see it happening. It would have to overcome the normal running pressure, *and* increase the pressure elsewhere in the system in compensation. For reasons I won't go into I have a pressure gauge plumbed in to the top of my V8 radiator which shows a reduction in pressure of 3lbs or so when the engine is revved compared to when it is stationary, no where near enough to flatten the bottom hose.
Paul Hunt

Bob; Do you recall which Toyota the switch you are using comes from? I'm using a variable
fan controller on both MG's, the sensing bulb goes in the top radiator hose. The controllers
allow me to set the fan cut in temperature as desired. The problem is that each time the
radiator hose is removed I have problems getting the leak stopped around the capillary tube.
A seal is provided but it still takes a careful application of sealer to keep it from leaking. On
the 68 GT I use a front mounted 12" electric fan from a Peugeot 505 and no mechanical fan
and so far it works well. I also run the fan and controller through a relay. I added a 3 position
toggle switch to my console. Center position is off, toggle up and fan works only when ignition
is on, toggle down and it works any time the controller senses enough heat to close it's
contacts. BTW the relay is fused.

On the 74 I use a 10" Hayden pusher auxiallary electric fan. I use a toggle switch on it but
toggle up is for manual on and toggle down for controller automatic operation. The Hayden
I have doesn't move enough air to cool the car without the mechanical fan.
Clifton
Clifton Gordon

This all sounds very familiar. In the 10 years I have owned my '64 B, I have had it run ok and run very hot. It seems as though the antifreeze has a bigger affect than I had thought. I used to run a 70/30 mix, because the bottle showed a higher boliling point, but the car would run hot when hot out. Now I run a 50/50 mix and change it every year.

At Indy '96, I had just installed new antifreeze and the car ran about 200 degree while waiting to get on the track. A few summers ago (with the same fluid that had been in for a few years since Indy), the gauge just about pegged when running in town. I think fresh antifreeze is very important.

I also did the following modifications which may or may not actually help.

1. I installed the plastic fan shroud. I had to modify it to get the 3-blade fan to fit in the hole.

2. I sealed the openings around the radiator with air conditioner foam.

3. I created a closed cooling system. I installed an overflow bottle from a Spitfire (yes, I know, but it was free and the right size). I ran the overflow hose into the bottle, filled the bottle 3/4 full, and installed a gasket in the radiator cap (the gasket came with the new cap I bought). Anytime I open the radiator cap, the radiator is always very full. Before the modification, it was not.

4. On hot days I still run the heater. I do plan to have the old radiator recored at some point. The one I have now is a 1994 or 1995 Moss variation. I had the radiator on my '76 recored with a larger and have been very pleased with it.


Hope this helps.

Bill Barge

A funny thing happend while dispensing advice - I picked up a couple of points that saved me from giving my daughter's MGBGT back with the fan on backwards. I have been doing a lot of work on her car, along with having the radiator recored (it had one of the less than adequate Moss replacement radiators in it) and replacing the 3 blade fan with a 6 blade version (one of the problems she has been experiencing has been running hot when stuck in traffic). As I said, The curve of the fan blade has been rather counter intuative for me, so after the posting from Jarad and Kim, I went down and looked at the fan I had put on my daughter's car. Comparing it to the 3 blade fan (with the notch oriented as the leading edge), I saw that the curve was in the wrong direction on the 6 blade fan (by the way Jarad, the concave side should face the engine). One can learn a lot by reading through the problems and solutions of others on this BBS. Thank you Jarad and Kim for saving me a red face down the road.
Cheers - Dave
David DuBois

Gentelmen - I am here to report that a cooling fan can be changed out on a 67 MGBGT without removing the radiator and at the sacrifice of only one knuckle. It would have been easier with a 3 bladed fan than with the 6 bladed one (only half as many blades for the bolts to hide behind). Again, thanks to Jarrad and Kim for keeping me looking like the smartest man in the world in my daughter's eyes. Cheers - Dave
David DuBois

I'm happy to have known something useful to pass along, Dave. As I said, I had only just learned that business about the notch in the fan blade a couple days ago from a friend on another BBS. (And I'll even forgive you the "gentlemen" reference!)
Kim de Bourbon

This has been one of the most educational threads I've seen anywhere about overheating. My 79 has overheated because of a bad fan switch and bad heater(water) valve. My 71 bgt has overheated several times the past 4 years. Loose top radiator hose, 2 bad thermostats, and ultimately a bad head gasket. When I took the 71 bgt head to an engine shop, he found that there were two small cracks in the head that had been "stitched" a few years ago. I'm still wondering if my temp gauge is correct since installing a new temp sending unit with the new headgasket and recently machined and balanced head.
sam c

Kim, if your 66B is positive earth and still has a dynamo you may want to think about converting to negative earth and fitting an alternator if you are going to run an electric fan - depends on the type of driving you do and what other electrical components you have fitted (additional lights etc)
Richard Atkinson

Good point, Richard. (It is still positive earth) I don't have any other extra electricals, other than a period AM radio. But that's one reason I'd hook the electric fan to a switch under the dash, so I could turn it on myself only when needed, say at a long idle in a traffic jam.
I think the dynamo could handle it, and chances are, it wouldn't be overheating at night, when I'd need the lights on.

I hope to get my recored radiator back in the car this weekend, and we'll see how she does. (At this point, I'm not keen to spend another $100+ .....)
Kim de Bourbon

Knowing that the cooling system pressurizes as it heats up and then having a pressure gauge indicate only a three-pound drop during revs would make me skeptical to the theory about the lower hose collapsing at speed had I not experienced it myself. Although not in an MG, I was traveling cross country and the temperature would climb so high that it would boil over at stops unless I drove a few minutes through a town a slower speeds before shutting down the motor. Having heard other lower hose problem being the cause of these symptoms I checked and found power steering fluid had soaked into that lower radiator hose and not only made it very soft, but even gooey. If not completely collapsed, this defective hose would have at least restricted coolant flow to the point of hampering proper cooling. I changed the hose and nothing else and the operating temperatures returned to normal. So I wouldn’t think this would be problem with a hose in good condition, but a defective one would be suspect.

This is more than theory because I recall buying radiator hoses in the past that contained a coil like spring that prevented collapse of lower hoses.

I never pondered whether the motor or the radiator caused more fluid resistance—it probably depends on each particular design. I do recall reading on a radiator web site that the sole advantage to a cross flow radiator is that the radiator cap can be located on the suction side of the radiator to avoid being pressurized by the incoming coolant.

Paul Hunt, too bad you won’t go into why you have a pressure gauge on your radiator, it sounds interesting. More interesting would be readings from different points in the system.
George Champion

Hi,
The bottom radiator hose should have a, I'll call it a spring, installed to prevent it from collapsing.
My 1980 MGB has a Pushe fan with only 2 blades is this normal. It runs hot in city traffic.

cec
Cec

Clif, did I answer your question in an email? I think I did but I have been so busy at home with remodelling that I forget.

For you or anyone else wondering about which sensor to use, I would say that it probably doesn't matter as long as you get the correct cut-in temp for the sensor's switch, and you get a matching threaded collar for the sensor of your choice. They should all be switches of the "normally open" variety and I strongly recommend the use of a relay to make life easy for the this thermal switch and get the best efficiency out of your fan.
Bob Muenchausen

Bob; I don't recall receiving an answer, I may have overlooked it. No problem, Both of my controllers
with the sensing bulb in the top radiator hose are now leak free and the coolant is fresh So I'll not worry about it until coolant changing time. Some VW sensors use the temperature range we need. Maybe some day I'll find an old catalog with the specifications of common sensors. Regards, Clifton
Clifton Gordon

For Paul,

I totally agree with your logic on the lower hose. However, I have had this very thing happen on the lower hose on my '73.

Replaced the hose with a new one (the only thing I did) and the overheating at freeway speeds immediately stopped.

I have never applied a great deal of thought to this but perhaps it can be explained by some thermodynamic reason that none of us has considered.

By the way, the seven blade plastic fan is an absolute no-no if you live in an area prone to flash flooding. I used to live in New Orleans. One day I hit a puddle about 2 blocks from my house. Water came through the radiator and the plastic fan tried to pump the water. What happened was that it couldn't and the fan blades curled toward the radiator. The end result was that the core of the radiator was cut almost entirely through at the bottom.

As a result of this experience I completely removed the engine driven fan and installed an electric fan with an adjustable thermostat. The adjustable thermostat is necessary to fine tune the temp at which the fan comes on. It is all too easy for the fan to come on when not necessary (coolant thermostat not fully open) and fight the coolant thermostat. What you end up with is the coolant flow being restricted.
Richard Smith

Driving in water that deep is extremely dangerous. What was the circumstance ?
.

In New Orleans the streets can flood very quickly and catch you. Also the streets are potholed beyond belief and rain can hide this so you're axle deep before you notice. If you don't drive in the water here, you spend a lot of time at home. How're those mountain roads treating you, Richard?
Terry

Terry didn't mention New Orleans is at or below sea level and how hard and long it can rain there.
I never lived there but I grew up in Mississippi and even though we had a few hills you could always
expect to have to drive through some deep water during a hard rain. FWIW, Clifton
Clifton Gordon

The circumstance was a puddle after a typical New Orleans afternoon shower. Would guess from memory that it was no more than 3-4 inches deep. The road (typical in New Orleans)had a dip where the puddle was. A combination of the dip and the fact that the puddle was very broad (about 6 feet across) and hidden in the dip made it not possible to avoid. As you can see it was not an extreme situation.

For Terry,

The roads up are are a blast! The mountains are pretty nice. I get to do more true sports car driving in a week than I could in 6 months in New Orleans.

Haven't been on the board for a while because of work but hope to become a regular again.
Richard Smith

Good to hear from you, Richard. Maybe you can make it back one day for our car show.
Terry

This thread was discussed between 16/07/2002 and 25/07/2002

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