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Overheating- Water Pump ?

Posted by PaulD 
Paul D
Amelia Island, FL, USA   usa
1979 MG MGB "Flash"
1979 MG MGB "MG Convertable"

I have had an overheating problem that started when I had a fan belt failure. After replacing the fan belt, the pulleys all turn and the alternator puts out 14+V at 700 rpm but after about 10 minutes the heat gage heads to the red zone. The last time , considerable steam/coolant came from the front of the engine. This leads me to suspect a water pump and gasket failure. Before I order these parts, is there any thing else I might need and/or any tests I should run.
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jrp316 Avatar
Josh Phillips
Kentucky, USA   usa
1977 MG MGB "Bomb"

Check your thermostat; it may have failed in the closed position.



Josh Phillips
1977 MGB (R.I.P.)
Kentucky

"Guess what? I got a fever! And the only prescription...is more cowbell!"
Chris T. Avatar
Chris Tyler
Garland, Texas, USA   usa
1963 MG MGB
1974 MG MGB

Paul,

Before going out and buying a new water pump. Make sure you fill the radiator and run the engine. Open the hood and inspect for leaks..You didn't mention where the coolant and steam came from. Could be just a bad radiator hose. But look for leaks first..

Hope this helps.

Cheers,



Chris Tyler
1963 MGB

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John Bamford
Colorado, USA   usa
1969 MG MGB

And a thermostat is a cheap replacement item. Also try to see exactly where the steam is coming from. Have you replaced hoses? There are a batch of connections up there and hoses can fail around the connections or connections fail. If the water pump is toast you can see it drip out of the weep hole steadily.



John Bamford
69 B Roadster Pale Primrose Yellow
100K, HS-4 Carbs, Rebuilt Head
Owned for 8 years
Denver, CO
Paul D
Amelia Island, FL, USA   usa
1979 MG MGB "Flash"
1979 MG MGB "MG Convertable"

I have removed and placed the thermostst in a pot of hot water. The thermostat opens at about 180 F. Is there any risk in replacing the housing without the thermostst so I can do the other suggested checks? Also, I live in Florida and will not likely use the MG in any cold weather. Can I run without a thermostat?
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rcedward Avatar
Rob Edwards
Raleigh, North Carolina, USA   usa
1951 MG TD MkII "TDC6000"
1969 MG MGB "182608"
1969 MG MGC GT "8806"
1969 MG MGC GT "8651"
1970 MG MGB GT "Donor"   → more

Don't run without a thermostat. If it's good, go ahead an reinstall it. If you still suspect it, get a new one (it's the same as a small-block Chevy thermostat, so any parts store will have one). Don't be tempted to go to a lower temp though -- a thermostat can only prevent an engine from running too cold, not too hot. You want the engine temp at least 180 or so; I prefer closer to 200. I run a 195 year-round, and NC summers aren't much different from FL summers!

HTH!



--
Rob Edwards
Raleigh, NC
http://www.mgcarz.com

If you're in NC, check out the North Carolina MG Car Club!
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Paul D
Amelia Island, FL, USA   usa
1979 MG MGB "Flash"
1979 MG MGB "MG Convertable"

I put the unit together without the thermostst so as to check for leaks and to see what temperature was reached without the thermostst. After nearly 1/2 hour the gage stopped rising at about half way between the C and H mark. I have no idea as to what the actual temperature of the coolant was at that point but there were no signs of leaks. Assuming the engine continues to run at this temperature without a thermostst, what is the risk? I am a retired mechanical engineer but no MG expert by any stretch!!!
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jrp316 Avatar
Josh Phillips
Kentucky, USA   usa
1977 MG MGB "Bomb"

The only thing that a thermostat does, in proper operation, is set the minimum operation temp; it won't do anything past that specified temp. Without a thermostat, the coolant is constantly circulating through the cooling system from startup to shutdown.

Running without a thermostat can cause overcooling, bad fuel economy from lack of engine heat, and even overheating in some cases. If you do choose to run without a thermostat, at least install a blanking sleeve (available from any MG parts vendor) into the thermostat housing.

The problem you're having does speak 'bad thermostat' to me though. Replacing it isn't a big deal; $5 part at any parts house. Since the engine did overheat, replace it as a matter of course.

Since you say that your thermostat checked out in testing, here's another test to check your water pump. Leave the thermostat out for this test. If you have an earlier B with the pressure cap on the radiator itself (later cars have the cap on the overflow tank), remove the pressure cap. Be sure you let the engine cool before this, or at least let the pressure inside vent out.

With the cap off, start the engine and look inside the housing where the cap goes. You should have a good, continuous flow of water. If so, and the leaks aren't coming from the pump, then your pump is fine.

If, after replacing the thermostat and doing the above test on the pump, you're still having issues, let us know and we'll check it out further.



Josh Phillips
1977 MGB (R.I.P.)
Kentucky

"Guess what? I got a fever! And the only prescription...is more cowbell!"
Paul D
Amelia Island, FL, USA   usa
1979 MG MGB "Flash"
1979 MG MGB "MG Convertable"

Thanks Josh,

Mine is a 1979 MGB with the seperate overflow bottle. Can I still run the check you suggested ? I am not sure why the "no thermoset" situation would cause overheating. Can you explain this situation?

bobmunch Avatar
Bob Muenchausen
PC, Oregon, USA   usa
1968 MG MGB GT "Traveler"

Try a new T-stat, and if the problem continues, first check for a surge of coolant in the top tank when you goose the gas.

Remove the radiator cap and have someone push the accelerator briefly to see if the coolant swells up in the top tank. If it does not, then you might move on to the water pump.

Once many years ago a friend had a similar problem and after going through all the other things it could be, he finally pulled the pump to find that a roll pin which held the impeller in place on the shaft had sheared and the shaft spun but the impeller barely moved and mostly by friction. Most impellers, especially today's common stamped sheet metal units, are pressed on to their shafts which are splined to help keep it from coming loose. However, there are still Acts of God and you could have a loose one. Good luck!



"All that my contradictory experiences demonstrate, sometimes, is that things and materials don't always follow the course of our commonly accepted thinking about them, but end up sometimes besting our knowledge of them."


SU Carb setup instructions ~ You don't need smog gear to need/use these factory instructions.
>>>https://www.dropbox.com/s/dgjgbxszv1h22hy/MG%20EMISSIONS%20MANUAL.pdf

MGB GT cutaway car photos can be found here >>> http://www.cibolas7.net/resources/cutaway.htm

A thorough guide to rubber rotary seals as used on your crank, axles, etc >>> http://www.rlhudson.com/Shaft%20Seal%20Book/index.html
rcedward Avatar
Rob Edwards
Raleigh, North Carolina, USA   usa
1951 MG TD MkII "TDC6000"
1969 MG MGB "182608"
1969 MG MGC GT "8806"
1969 MG MGC GT "8651"
1970 MG MGB GT "Donor"   → more

PaulD Wrote:
-------------------------------------------------------
> Thanks Josh,
>
> Mine is a 1979 MGB with the seperate overflow
> bottle. Can I still run the check you suggested ?
> I am not sure why the "no thermoset" situation
> would cause overheating. Can you explain this
> situation?
>

Running without a thermostat can allow the water pump impeller to cavitate, at which point it will stop pumping altogether, which will cause it to overheat. Do yourself a favor -- put a thermostat back in! :-)




--
Rob Edwards
Raleigh, NC
http://www.mgcarz.com

If you're in NC, check out the North Carolina MG Car Club!
http://ncmgcc.org
John D. Weimer Avatar
Cape Girardeau, MO, USA   usa

Another thing, When you leave a thermostat out the water passage at that point is no longer restricted and coolant can flow through the radiator so fast at road speed that it doesn't have time to cool. Old flat head Ford V-8s would overheat even at idle without their thermostats, they had two water pumps, and 'stats.



Edited 1 time(s). Last edit at 04/27/2006 07:13PM by John D. Weimer.
jaybird Avatar
Janel Demick
Metro St. Louis, USA   usa
1966 MG MGB "Binabox"
1975 MG MGB "Emma"

Weimer, that avatar of yours looks just like my brother-in-law but he's bald. Swear to God. It's disturbing. We've found Alvin's long lost twin.



Live your life in such a way that when your feet hit the floor in the morning, Satan shudders & says...
'Oh shit....she's awake!!'
Paul D
Amelia Island, FL, USA   usa
1979 MG MGB "Flash"
1979 MG MGB "MG Convertable"

I am convinced. I bought a new thermostst at Auto Zone and will install it tomorrow.
jrp316 Avatar
Josh Phillips
Kentucky, USA   usa
1977 MG MGB "Bomb"

I have a '77 MGB with the same setup as yours, with the pressure cap on the overflow tank. With the thermostat out, you could try removing the thermostat housing plug and check for flow that way; I've personally never tried that, and you would definitely have to be ready to kill the motor in the event that it started spewing coolant, but it could at least give you some indication of water pump function.

One could also remove the top hose at the rad and direct it into a good sized bucket, then start up and check for steady flow. Actually, that sounds like the better idea of the two; that would save you from having to mop up coolant. But as soon as you realized a good steady flow, just cut the motor and you're done with that.

The MGB is the only car I've worked on that filled through the thermostat housing. Plus, the later model rads are the only ones I've seen that had no pressure cap. Removing the rad cap and running the motor has been the way I've always checked for water pump function in other cars.

Since you did overheat the engine, replace the thermostat anyway. If the problem persists, test the water pump as I described above. On street cars, a thermostat is always a good thing; the only cars that are even recommended to remove them are racing and autocross type cars. Even then, those cars fit a blanking sleeve to the housing. A thermostat is a necessary thing to have, for all the reasons listed in the previous posts.

When I first bought my B, the thermostat was stuck open; basically like having no thermostat at all. The temp would not stay anywhere near consistent; I'd go from overcooling to overheating at the drop of a hat. Replaced it (and subsequently a defective electric fan), and haven't had a problem since.

How long has it been since your last block/rad coolant flush?



Josh Phillips
1977 MGB (R.I.P.)
Kentucky

"Guess what? I got a fever! And the only prescription...is more cowbell!"
Paul D
Amelia Island, FL, USA   usa
1979 MG MGB "Flash"
1979 MG MGB "MG Convertable"

Josh, I have ordered a new water Pump and gasket. I have never flushed the cooling system but the entire engine was rebuilt about 600 miles ago,. The original owner had an overheating problem and fried the engine. I bought it in 1997 and like many projects , just got it running last October. Perhaps I should do a flush when I install the new water pump, since I will have to drain coolant anyhow.

Paul
jaybird Avatar
Janel Demick
Metro St. Louis, USA   usa
1966 MG MGB "Binabox"
1975 MG MGB "Emma"

Want me to put it in for you? I'm an expert at water pumps now.
grinning smiley



Live your life in such a way that when your feet hit the floor in the morning, Satan shudders & says...
'Oh shit....she's awake!!'
BumbleB74 Avatar
William Milholen
Tidewater VA, USA   usa

PaulD -

When you do come to a point of needing a new water pump, consider the local option of NAPA. You'll probably come out ahead in the long run, and get a warranty that you can
act on quickly should you ever need to.

I hate ordering heavy parts when you can get them locally!

William



1974-1/2 Roadster, "Bumble Bee", Corvette Yellow - in shambles, wire wheels
1976 Roadster, un-named, Sandglow - "driver" condition (stock + 32/36 Weber DGEV, cast iron header, 25D distributor), bolt on wheels
Paul D
Amelia Island, FL, USA   usa
1979 MG MGB "Flash"
1979 MG MGB "MG Convertable"

I have already ordered the pump and gaskets from The Little British Car Company. I was unaware NAPA would have a water pump for a 1979 MGB.
jaybird Avatar
Janel Demick
Metro St. Louis, USA   usa
1966 MG MGB "Binabox"
1975 MG MGB "Emma"

When I went after one for Emma, NAPA, Autozone, Advanced Auto and O'Reilly ALL had to special order the pump for me. And it was twice as expensive as the pump I got which cost me $36. (Moss)



Live your life in such a way that when your feet hit the floor in the morning, Satan shudders & says...
'Oh shit....she's awake!!'
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