So driving my 71' B today in 95 degree Cali heat and got to a hill. Started up the hill and my temp gauge slowly made its way till it was almost pegged at H. I couldn't pull over so for about 90 seconds I had to keep going with the gauge at H. After that I reached my destination and immediately got out and opened the hood. The radiator fluid was bubbling but no steam. Should I be concerned here?

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1971 MGB

I would check for leaks and that the coolant level is normal. Some use electric fans for the summer. I was camping at the KOA last week there. It was about the same temp last week.

No...
Remember; The gauge in these cars show a RANGE. If pegged at "H" it simply means that it's at the upper end of it's designed range. More than likely if you had hit it with an IRT, you'd have seen temps around 210 or so...nothing to be concerned with so long as it returns to whatever it normally runs at. Well...I should say I wouldn't be concerned.

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"One test is worth a thousand expert opinions"--Alvin "Tex" Johnston...Boeing test pilot.

73 MGB. Tires: Round, black, hold air. Oil: Sometimes old, sometimes new...always slippery. Oil filter: Yellow, usually full of oil. Carbs: 2 SU HIF. Distributor: Yes. Headlights: Not that bright but bright enough. A bunch of other stuff most cars have but not really important enough to itemize. Oh, wait...it has a cool sounding exhaust with stickers on the chrome tips. Really slays the ladies...

I had the electric fan going but that hill was a killer!

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1971 MGB

Drop the antifreeze percentage to 25% or less, or straight distilled water for the warmer months. Check the fan belt tightness.

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Be safe out there.
Kenny

Your picture shows a Tourer, if the hood is down, putting the heater on max towards the windscreen with its fan on would've helped enormously. Hot wind over your head is something I experienced in the many years I did not have the more powerfull Kenlowe 13" pusher and an extra 9" aftermarket puller one I have now in. Even without any auxiliary fan my B survived on the heater during the 80's

40+ C is above 100F right? Climbing this year on these temps with both of my fans on was OK even without my heater switched on....

PS Using a 74C thermostat each and every summer gives me some more minutes uphill in the temp range below the automatic onset of these fans




Edited 1 time(s). Last edit at 2017-07-17 10:41 AM by Donthuis.

Lower thermostat and electric fans will make little difference in this situation, the temp is hill climbing under heavy load. I assume this was not stop & go traffic and above 30mph?

Condition/history of radiator? (a 15 year old radiator will not have the cooling capacity of a new or recently serviced unit)

Fuel mixture? (possibly lean condition under load?)

Timing? (total advance and vacuum advance setup?)

As noted above, checking the temp with a IR thermometer would have told you if the car is really overheating. On my car, half way between N and H is only about 195deg, I'm sure 210deg would be at the H.

I forgot to mention the pressure the radiator cap is designed for. 1971 is probably with the 10psi cap, but if your radiator is in good shape, nothing prevents you from mounting the later 13 or 15 psi cap. Even 13psi is only one bar, a very low value for the system.

The higher the pressure, the higher the temperature the waterbased cooling fluid boils on. Of course if you use water +antifreeze and not waterless coolant. Wellknown engine tuning specialist Peter Burgess explicitly warns against using anything else but waterbased coolants, if you do not, the warranty on his cylinder heads is void for a reason...

PS Mission creep is close by, one can tie innumerable issues to a simple cooling question

I just completed a major road trip in my 1971 B that included a long haul at 75+ MPH on steep hills at almost 100F. The temperature gauge needle did not move off the N.

I will grant you that some fluctuation of the gauge under these conditions is normal, but I would be concerned with the needle on H. Double check the reading using an infrared thermometer - your sender may be out of calibration (there have been a lot of problems with recent replacements - see the thread on this issue).

If you are over 210F or 215F at the thermostat housing I would be concerned. Check that your thermostat is opening completely and that your radiator is not clogged (inside or out).

I would also recommend 15w-50 synthetic oil - synthetic oil can take higher temperatures than conventional oil.

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Terry Ingoldsby
terry.ingoldsby@DCExperts.com

If it happens again, try not to remove the radiator cap until your gauge begins to go down. The fact that you mentioned the radiator fluid was bubbling tells me that when you remove the radiator cap, the pressure above the fluid became ambient and the water reached an approximate boiling point of +212F or 100C. If you are running 50/50 glycol/water mixture, the boiling point would be above 230F according to my best guess without any steam tables handy. Boiling radiator fluid creates gas pockets in the cooling system and if you don't purge the gas pockets after your overheating experience, you will get hot spots on the block because the gas has displaced the coolant. Also, you run the risk of creating a glycol/water geyser and getting scalded in the ordeal. I learned this lesson the hard way many years ago on my dad's Buick LeSabre.

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"The difference between genius and stupidity is that genius has its limits."
-Albert Einstein

Roy - Good advice.

Don't be overly concerned but do have your cooling system flushed thoroughly. These cars were designed as daily drivers and should not boil over or heat excessively.
You simply need to perform some maintenance.

B

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Check your ego Amigo!

I would keep your car running until it cools. Turning off when it's that hot can be problematic.

Peter C

I very much appreciate everyone's responses here.

I'm going to look into why this happened and try and narrow down the cause.

I'm going to check the oil and make sure there's no sign of a blown head gasket or cracked head...i.e. water in the oil. I also let the car cool down and restarted it and the engine sounded normal. No leaks to speak of either. Can I assume I didn't damage the engine here if all of the above is ok or are there other things I need to look for? Hoping I got away with it this time.

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1971 MGB

Insert the candy thermometer into the radiator filler neck and read the coolant temperature to and including once the thermostat opens and the coolant is flowing across the top of the tank. Depending on the ambient air temperature cardboard in front of the radiator may be necessary to get the coolant warm enough to open the thermostat. If there are lots of bubbles the head gasket is suspect. The candy thermometer is inexpensive and available in most grocery stores. The accuracy can be checked with a pan of hot water on the stove. I have a 1971 MGB and this is how I verify that the thermostat is functioning properly.

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Be safe out there.
Kenny



Edited 1 time(s). Last edit at 2017-07-17 07:00 PM by dipstick.