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MG MGB Technical - Overheating.. Water pump question

I need your help!!

The good news is I made it home from Watkins Glen, NY. Normally a 4 hour trip, but today it took 6 hours. The 1979 MGB had a few "heating-up" problems while running around the back roads of the Glen. The needle almost hit the red mark. My normal driving of the MGB is local trips... this is my big event of the year with the round trip being about 600 + miles.

On the way back after about 25 miles it heated-up and did not come down to a normal range (stayed to close to the red line).

Info: New radiator, hoses, thermostat, radiator cap, installed 2 years ago... with new anti-freeze too.

Get home solution: I took out the thermostat, made a "home-made" gasket (I was along the road, not in a garage). Temp dropped down to about midway on gauge, but would still "climb" a towards high side at speed (60-65 mph, even down hill).

Now to fix: WHAT DO I NEED?? (besides a real gasket, replacement thermostat)... The water pump is not leaking, or making any noise... but could the vane inside it be worn out? Requiring a new water pump?

Please help, make suggestions, tell me what I need to do/buy/replace... it looks as if I could do this myself.

Thanks for ALL of your help,
Don 1979MGB
Don

Don: you may want to check the temp gauge for accuracy. One thing you may want to do if this condition should occur again,is to turn the heater to the "ON" position. This will draw some heat from the cooling system and cool the engine down to an acceptable temp range. Also, how old is the radiator?

Let us know how this situation plays out.

cheers
Gary :>{D
79 MGB
gnhansen

Don,
Certainly check or have checked the gauge for accuracy as Gary mentioned. They can become erratic over time and give false readings.

Removing the thermostat and having the temp go down suggests it was not operating correctly so a new one would be my choice.

Finally if the temps vary as the air flow through the radiator varies then it seems your cooling system is not operating at full effiecency despite the two year old radiator.

I would have it reverse flushed and see wha comes out. It may be partially blocked from scale and other rubbish being deposited there from else where in the system like the heater core or hoses.

Please post what you find to help others.

Cheers , Pete.
Peter Thomas

Make sure nothing is restricting air flow through the radiator, such as leaves and/or bugs.
Kimberly

Forgot to add, yes the vanes in the water pump can wear away reducing the flow of coolant.
Kimberly

Were the vanes in the pump plastic? I have heard of them breaking off and not only not pumping coolant, but also blocking cooling passages. This was not on an MGB BTW
Stan Best

Thanks for the replies!!

I will not be able to do much for now, maybe Friday or Saturday. Here's my list of to-do's.

1. drain out coolant. Back flush radiator/engine.. I have found this info in a couple of my books. Seems simple enough.

2. order a blanking sleeve and new gasket (instead of a thermostat).... I don't use the MGB much in cold weather, nor drive it in the winter months.

3. fill first with "water" and check results. Then replace with a quality coolant.

At the time I installed the new radiator..etc. the parts included a new temp sending unit in the radiator too. The one on the dash seems to work fine.

I have 75,300 miles on the MGB. It has a weber/header instead of the original set-up... no problem when it runs... just this recent heating problem.

The termostat probably was the "concern"... I was also concerned about the water pump, but would hate to change if there isn't a need to. Any way to check these to determine amount of "flow"???

If you have any tips on how to check a water pump, please let me know how. I'll hold off on ordering parts until I get some tips.

Thanks,

Don 1979 MGB
Don

I forgot to add this to my note. The cap is 15 pounds pressure, the Thermostat was a 160 degree. This made the gauge read about midway "before" my overheating problem.

safety fast,
Don
Don

Don: I forgot to mention, try the temp sending unit and its connection. Electrical items can be misleading even if these items are new.

cheers

Gary :>{D
79 mgb
gnhansen

Hold on! First check the engine *is* running hot with an independant instrument. Is the electric fan cutting in and staying in? If not I'd suspect indication rather than engine.

If it *is* hot then with the electric fan having been running for a while feel the radiator. If the bottom is cool that indicates greatly reduced flow through the radiator. Could be blockages anywhere, remove the thermostat as a diagnostic, if the thermostat isn't the problem it will still happen but probably take longer. Could be a bad pump.

If much the same heat at the bottom as the top then either the engine *is* producing too much heat or the cooling system isn't getting rid of it. Check the timing, including checking the timing marks against true TDC of the pistons. Check a front mounted fan is pushing air through the radiator towards the engine, or a rear mounted fan is pulling air through the rad towards the engine, i.e. in the same direction as ram air in both cases. Check the orientation of the blades: A metal fan usually has one outer corner curved and one sharp cornered, the curved corner is the leading edge. Plastic fans usually have one thick edge and one thin, the thick is the leading edge (like an aircraft wing). If either fan has scalloped blades then the scallop or concave side should be facing the engine. Do you have any fancy badge bars or foglamps in front of the grill? Does the front valance have the cut-outs to allow ram air through to the lower part of the radiator? Is the 4-cylinder supposed to have a shroud to direct this air through the rad and air cooler? The V8 does.
Paul Hunt 2

Thanks Paul,

I was hoping you'd provide some of your advice. "Before" I order parts, I'll run the engine and see if the electric fan kicks in, and also check the radiator for cool spots to determine if there is any blockage.

This is a '79 with an electric fan (2) set-up... will also check to make sure the fans are blowing thru the radiator.

Inside the engine bay I do have the mud guard (original), but I'll have to check about the openings on the valance. I do NOT have any badge bars or clutter on the front opening to restrict the air flow.

But... is there still a 'simple' way to check the water pump??? could a hose (heater?? with it set for heat) be diconnected to check the flow?? If you have any tips please pass on.

Looking forward to your reply,
Don 1979MGB (4 cyl)

Don

Not using a thermostat can cause problems by allowing the motor to be overcooled.
Kimberly

Don; I know of no way to check the flow of a water pump on the car. Off the car about all you can do is visually examine it. I have never seen water pump impellers wear out, but all I have ever seen had cast or stamped impellers. I suspect your water pump is good unless your problem is a gradual rather than a sudden change.

Clifton
Clifton Gordon

Great replies!

Kimberly,
I would prefer to run the engine on the cool side, instead of risking boiling over. For the past seven years the "B" only aveaged about 1,100 miles a year (PO only put 10,000 on it, he owned it 12 years and had trouble with it overheating). With the replacement parts I've already done, it "did" run cooler until I retired and started to drive more (3,000+ already this year).

My plans are longer trips, maybe doing about 5,000 miles per year. I think if I follow the basic procedures to flush-out the system, etc. it should be good to go.

I understand you are 100% correct that it would be better to run with a thermostat for best mileage/emmissions, etc.

Clifton,
Just trying to "rack my brain" to find a way to check the water pump. I did a lot of reading, and if it is not leaking or making any "bearing" noise, then it should be ok. The change was kind of sudden, so I think there was a thermostat fault (failure) or there could be a possible blockage. I will flush the system out.

Thanks for your thoughts/knowledge, have a great evening.

Don 1979MGB (could say a "hot" MGB!!)
from Penna.
Don

HI Don,
First off, if it's not boiling over, it's not overheating. You should definitely make sure all is working properly and verify the gauge with an accurate thermometer. With a 195ºF thermostat, my gauge settles around the 3/4 mark -- halfway between 'N' and 'H'. If I'm pushing the car hard, it'll climb up to nearly 'H'.

A few things to consider:
Many people erroneously believe a cooler thermostat prevents overheating -- it doesn't. A thermostat can only control the engine's MINIMUM operating temperature. Think of it this way: you're driving in the mountains, and your engine is at normal operating temp with the thermostat open. You crest a hill and start a long downhill run. The engine is just loafing along and there is lots of air going through the radiator so the engine begins to cool down. The thermostat senses that the engine is becoming too cold so it begins to close. This slows the water through the radiator (and will eventually stop it if needed) so that the engine can maintain the proper temp. Now you're driving along, the engine has returned to normal temp, and the thermostat is again open. You begin a long, steep climb. The engine is really working hard and making lots of heat. It's temperature is rising, but there's nothing the thermostat can do -- it can only open or close, and it's already fully open. Eventually, if the rate of heat production excess the rate of heat disposal, the engine WILL overheat. The answer is to make sure that the heat transfer ability of the radiator and cooling system is up to snuff. Also, Barney Gaylord on his MGA pages recommends running a thermostat blanking sleeve AND a thermostat. He argues that this approximates the design of the original thermostat, which had a sleeve that would drop down as the thermostat opens to block off the coolant bypass passage in the head. The passage is there so that the coolant can recirculate when the thermostat is closed, and blocking it off means more coolant through the radiator and less recirculating.

Incorrect ignition timing (either because of incorrect initial timing or because of an incorrect advance curve) creates excess heat. There's a sweet spot at every rpm and load where the engine makes the most power and least heat. It's the ignition advance's job Carl Heideman at Eclectic Motorworks says that varying from that sweet spot costs you 1 hp for every degree of advance. When you burn the fuel, it releases a fixed amount of energy -- if that energy doesn't become power to turn the wheels, it instead becomes heat. Carl said that rubber bumper cars seem to like about 35º advance at 3500 rpm. If your advance mechanism is worn and you set your ignition advance at idle, then you may not be getting the expected advance at higher rpm. He said he's seen cars that, although the idle setting was correct, at 3500 rpm they only had about 20º advance. The way to check it is with a dial-back timing light.

Plain water at atmospheric pressure boils at 212ºF, but a 50/50 mix of water and antifreeze boils at about 230ºF. When you pressurise water, you increase its boiling point -- 3ºF for every psi. So a system with 50/50 water and antifreeze and a 16 psi cap won't overheat until about 280ºF -- well above 'H' on the gauge!

For maximum power, efficiency, and engine longevity, you want to run the engine as hot as is practicable. Both Peter Burgess and Smokey Yunick recommend hot thermostats -- Burgess says "The ideal 'stat is 88 degrees Celcius (190ºF) ." In his book "Power Secrets," Yunick says:

Quote:
" It is easy to see how overheating can be a problem, but I think some racers overlook the fact that it is possible to 'overcool' the engine. Some guys go to great lengths to keep the engine temperature down to 180 degrees. And, though the engine doesn't overheat, they don't realize that they're putting energy (heat) into the cooling system that could be used to produce power at the crankshaft.
Running the engine at 180 degrees will drop the overall horsepower by 2%-3%. For max power the cooling temp should be at least 200 degrees...."

I run a 195ºF tstat year-rond in North Carolina, where the boilerplate weather forecast from June to September is "Upper 90s, with a chance of afternoon thunderstorms." Sometimes the weathermen are wrong though -- sometimes it's hotter than that... ;-)

So I guess that's a very long-winded way of saying "Make sure the cooling system is working correctly, and as long as it is, don't be overly concerned about it."

HTH!
Rob Edwards

Oops! Not sure what happened there. That nonsense sentence should read:
"It's the ignition advance's job to make sure that the ignition occurs at (or near) that sweet spot. Carl Heideman at Eclectic Motorworks..."
Rob Edwards

Rob, thanks for the information on how the cooling system works.

A "question"... I ordered a blanking sleeve. Now if I can get the system flushed out, make sure there isn't another problem, should I use "both" the thermostat and the blanking sleeve?? any special way this will need to fit so I avoid having something in backwards/upside down?

I am going to "check" the 160 degree thermostat by placing in water, and bring the water to temp (I have a cooking temp) and see at what temp it opens. Maybe I'll check this a few times just to make sure it works before placing back in the MGB.

Looking forward to your reply about the blanking sleeve/thermostat combination.

Safety fast (when I get it running again)

Don 1979 MGB
Don

Don,

Great stuff above but I wonder about two 'little' things which I don't think have been covered.

If the cooling system rework is a couple of years old you could have a stretching fanbelt, or the tension may be slowly slipping at the alt bolts. That might also explain the better running with stat out but deteriation on going to higher speed.

The other thing can be a deteriorating bottom hose which can contract and restrict coolant flow. This could also happen with a hose of too soft a construction, even if only a couple of years old. I have seen some hoses over here which really are pushing the limit on lightness in construction.

Also, a thermostat can be checked in a pan of water brought to the boil and the opening pattern checked with a thermometer. If Ok I'd be inclined to reinstall it whilst seeking a solution to the 'problem'. If you are going to run with one in place its presence should be factored in to the solution.

Good luck

Regards

Roger
Roger T

Don't know about a blanking sleeve *and* a thermostat, I was under the impression that it was either/or. Blanking sleeves are used by the racing fraternity where the engine is fully warmed at a standstill, and there is no need to reduce coolant flow to prevent the engine being overcooled in very cold weather. The sleeve controls the flow to much the same rate as a fully open stat, without this you can get a much higher flow through the engine, localised turbulence and hence hot-spots. The engine runs more efficiently at its design temperature, running it cooler does no good and can do harm. It is certainly harmfull to run the engine on the road in winter without a stat as the engine may never get anywhere near the correct temperature and in nay case will require extended use of the choke. Speaking for myself I only recommended use without the stat purely as a diagnostic aid, to see if it made any difference to the ultimate running temperature.

A sudden change could still be a pump failure, with something breaking off and blocking a passage.

Don - what are the fans doing when the gauge reads high?
Paul Hunt 2

Good afternoon Roger,

I will not be able to "hunt" the problem down until Wednesday (blockage/belt). After I read your post I checked out the thermostat. Here is the results using a pan full of water to completely cover unit. Used a thermometer to check temp:

160 degree thermostat.

Closed at 160 degrees
Opened by 180 degrees
at 200...opened
at boiling..opened.

Cooled water to 180, remained opened
Cooled water to 140, closed.

Repeated test 3 times, same results...

I "wonder" how many times we "curse" the wrong part??

Bottom hose is new, but I'll check it over.

The recommendation about checking the fan belt will be done. I never installed a new belt (PO.. no idea how long since he put one on). I've carried a new one along in the trunk... guess It should part of the solution to my problem.


Paul, I'll know more about the fans when I start the "hunt" Wednesday... I'll post my results.

Thanks for your support!

Don 1979 MGB
Don

Yup -- blanking sleeve AND thermostat. Drop in the sleeve, put the thermostat on top of it, then the gasket and housing. Maybe it's a placebo effect, but my engine temp seems better regulated since I installed the sleeve in conjunction with the tstat.

Here's what Barney has to say about it:
http://www.mgaguru.com/mgtech/cooling/cool_103.htm
(click the right arrow button at the bottom of the pages to advance to the next page. There are about 4 pages you'll want to read).

I'm not sure about his recommendation to drill a hole in the thermostat flange, though. I found that a 1/8" hole in my thermostat prevented it from *ever* warming up in very cold weather. I'm at a loss to explain how so small a hole could cause that, but it seems it did.....

I agree with Paul: NEVER run a street car sans thermostat, with the possible exception of diagnostics.

HTH!
Rob Edwards

Rob.... wow!! thanks for the link! I'll hunt down any/all other problems and now that I already have the blanking sleeve ordered I will install according to the MGA link (I understand a small hole will need to be drilled in thermostat edge).

Don... soon to not have a "hot" MGB..
Don

Improper timing can cause overheating as well. And I've hears that cast iron water pumps cool better (though I run an alloy one with no problems).
D.A. Abbott

"Here's what Barney has to say about it:
http://www.mgaguru.com/mgtech/cooling/cool_103.htm"

Double check to insure that the water port in you head matches Barney's picture. I was thinking this only applied to the MGAs & early MGBs.
Carl Floyd

My ca-1974 head did.....
Rob Edwards

This thread was discussed between 11/09/2006 and 16/09/2006

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