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MG MGA - Running warm on the interstate and air filters..


Hey guys,

Had the '56 'A out the other day. Ambient temp here was about 80 dF and the car seemed to be running a tad bit warm, mainly when underway on the interstate (temps about 200 dF). When driving around town, it would drop closer to 190 dF. Granted, last time the car was out, the ambient temp was about 60 dF so the car kept plenty cool. What would be considered normal running temps for the MGA in 80+ degree weather? My '67 B-GT usually never goes above 180 unless sitting in hot traffic for extended periods, in which case, it will climb to 190-195. Since the MGA is still new to me, I need to work my way around it a little more to become 'comfortable' with its habits.

Also, can anyone confirm that the original type air filter elements are of different thickness? The filter on my rear carb is more of a pancake-type and the front filter is a thicker (i.e. "normal" thickness) one.

Thanks all!

Aaron
Aaron Greenberg

Aaron. Temperature is a common item on the BBS. A quick look through the archive should turn up a number of things to look at.
As a quick thing to do, check the radiator core. Many replacements have a high number of cooling tubes (downward direction) that don't allow air to flow so freely as the original. This is okay at low speed (in fact often better than the original) but at high speed the lower air flow reduces cooling.
Best is if you can see an original radiator and compare with your own.

There are many other things that can also affect cooling such as fuel mixture, timing, grill slats etc.
Best to look in the archive though and then work through the list you find. Check out Barney Gaylord's website as this also has some good advice.

Neil

PS, wish it was warm enough to overheat here!!
Neil Purves

Both air filters should be the same.
Neil McGurk

Aaron, check the thermostat. I just got my Coupe on the road after a 2 year restoration and it was running hot, around 195-205 degrees. I replaced the 185 df thermostat with a 165df one and now I'm running between 175-190.

Andy
Andy Preston


Thanks all, I have a 160 degree t-stat on order along with some other goodies from Moss. I checked the level and condition of the antifreeze today and that looked fine. I was also thinking of ordering the fan shroud that Moss sells, just to have extra precaution.
Aaron Greenberg

Andy,
195-205 is not hot. Probably about right and the designed running temp.
At 195, your 185 thermostat should already be fully open. Your 165 thermostat just opens 20 degrees earlier. Changing thermostats does not explain the running temperature difference, unless your original 185 thermostat was faulty and was not opening fully.
Peter.
P. Tilbury

Ditto what Peter said, lower t-stat will not help cooling if it runs normally at 190+, it just opens earlier and increases initial warm up time.

I tried a 160 t-stat in my car last summer (wanted to try one of the original moving sleeve units), and it always runs at 190+ in warm weather anyway. The low temp t-stat was a problem for winter driving (40dF or lower ambient temperature) when it needed constant light choke setting to run right at 160dF, and the heater was not much use. I then installed a 195 t-stat, so the heater works a treat in cold weather. It now runs about 200dF minimum all year round, and exactly the same running temperature in hot weather as it did before, regardless of what thermostat is used.

If I do anything with t-stat this summer I might try to find a 180-185 modern style t-stat and install it along with the blanking sleeve to close the bypass port. Ive been itching to try that for some time, even bought the blanking sleeve a while back.

If you haven't heard, I highly recommend installing a fan shroud, which helps immensely during slow driving in hot weather (but won't do much for carburetor vapor lock issues).
Barney Gaylord

Barney, I have tried many, many different thermo's, recor's, fluids, Complete engine rebuilds on and on for well over 40 years with my 1956 MGA and it still over heats. Currently I have a Blanking Sleeve with a 168 or 170 thermo. and it starts out fine until it warms up and you should see the Temp. gauge. It go's from about 170 to 200 in about 5 seconds. Its really weird. I then open up the heater and it cools down to about 195. I'm going to try an electric fan next. Do you think I should try the Blanking Sleeve with thermo. all in one. Tom
Tom Peotter

I run with a blanking sleeve only most of the year, a 190 stat when the chill hits the air for the warmth. Works for me. Marvin
Marvin Stuart

I'm running an 85 degree c old style bellows and collar thermostat with a 7lb radiator cap on my 1958 1500 MGA. Engine runs at about 190 max on the gauge and everything is fine until the engine is stopped, then the temp climbs towards 212 and coolant is expelled from the overflow pipe. This continues to happen at nearly every engine stop until the rad needs topping up. Im am not overfilling the radiator (1/2" below the seal orifice or 1" of coolant in the filler neck)and the block has been cleared of sludge and scale in the water jacket, so what's going on there?!
Lindsay Sampford

Too much coolant in the system. If you fill it to the top, during the first heat cycle it will push out at least a pint, maybe a pint and a half. When it cools down it will leave that much air space in the top tank. That leave the coolant lever very near the bottom of the horizontal filler pipe, so it's hard to tell how much is in there. Leave it at that level. If you top it up any at all it will just push out the excess next time it runs.

My solution to not being able to see the fluid level when cool was to install a recovery bottle. Not the expanded fluid goes into the bottle and is pulled back into the radiator when it cools. The top tank is always full with no air space, and I can watch the fluid level in the clear recovery bottle without removing the cap.
Barney Gaylord

Tom your system sounds like it has has too little cooling capacity. Either a partially plugged radiator or an inefficient core. If adding cooling capacity by running the heater fixes the problem you have your answer. A cooling system that can cool 101% of the heat will work just fine. A system at 99% will over heat and blow out the water. Your system is too marginal. To work well it needs to be able to dissipate all the heat at any ambient temp.
Air flow through and not around the radiator is important. That is why a shroud helps. On my Mazda rotary powered MGA the final fix was sealing across the top of the radiator to the bonnet with foam tape and capping the air hole on the left that normally feeds the carbs cooler air. That with a 4 row core and 2 cooling fans did the trick. This car develops almost 3 times the HP that the 1500 it replaced made. As you should know HP is heat. I have never had an unfix able over heating problem in a stock A and have owned 7.
An improperly set up engine can cause overheating problems also. Too much timming or too lean are the biggest mistakes. Fatten the mix a flat or two and back off the timming a degree or two and follow the results.
R J Brown

This thread was discussed between 27/04/2009 and 18/05/2009

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