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MG MGB Technical - Is My MGB Running Too Hot?

This is on my 72B.

I'm running a 160 degree thermostat. Radiator was flushed out (at home) last year. I combed out the fins on radiator last year. Last year no more temperature problems.

On cooler to upper 70 degree days, temp gauge needle sets one needle width past "N".

Valve job this May, afterwhich I put water in the system while checking for leaks for a week or so. Then I changed oil and flushed out cooling system and replaced with 50/50 water/antifreeze. I lose no coolant. Coolant level is just below filler neck.

It has been in the 90s for days. When it is in the 70s I don't have this problem.

Temp gauge now reads 2 needle widths to left of Hot - which is past 3/4 to 7/8 of the way to H. I'm afraid it would go hotter it I kept going today.

Using a temperature sensor on direct readings and infra red I get 200-210 at temp gauge and at thermostat housing. I get readings of 185-190 off of head and valve cover.

The temperature reads the same from left to right across radiator, but gets hotter going up to top of radiator. (160-165 at bottom, 170-185 in mid section, 195-205 below reservoir and 200-210 along reservoir).

I have noticed what looks like coolant very slowly dripping from several inches below thermostat housing, but it was too hot to check to see if this is coming from the seep hole in water pump or elsewhere. I know its not oil dripping. I can check this out in a hour or so.

Its obvious temperature in radiator and at thermostat housing and along head is in the 200+ degree range. Temp gauge is getting close to H. So it appears gauge is accurate.

To me the even temperature range from bottom to top of radiator may indicate heated coolant is moving through entire radiator, and radiator isn't blocked anywhere compromising cooling capacity. I'll add that coolant, and previous water stay very clean.

Engine is running rich, which may be contributing to high temp, but temp is high when crusing along on open country roads at 50-60 mph. I haven't confirmed if temp drops when setting still and idling, but I'm suspicious this happens.

Is this safe to operate at this temp?

Is this normal for 90 degree weather conditions?

Is there anything I can do to lower temperature?

Engine does have an oil cooler too.

Thanks for the assistance, and appolgies for my as usual long posting.

RW Anderson
Stillwater, MN
R.W Anderson

IMHO This is a normal reading for temps over 90 degrees. You could add a electric fan this might help some in traffic. As you drive off the tempature should fall between 180 and 190. The Carbs might be running lean or the timming is retard.
James D

The engine would probably run cooler with about a 25% antifreeze mix. You aren't overheating if the coolant isn't boiling or being pushed out. An infra red thermometer is good for checking where you have temperature changes but it measures surface temperature and the coolant temperature may be above or below the readings seen on the surface. That said, I would want to verify what the exact coolant temperature is with a cooking or some other contact type thermometer. Knowing the exact coolant temperature will tell you if you have cooling issues or a gauge problem.

Running too rich will usually cause an engine to run cooler. If you do find the gauge is correct you don't have a lot of safety margin. My car runs about mid range to a needle width above mid range when temps are around 90. I have a 180 stat and use 25% antifreeze. I also have a high efficiency core in my radiator.

Have you ever had your radiator tested and cleaned at a radiator shop? It may help.

Clifton
Clifton Gordon

Even in the UK we get 90 degree days but my 73 never runs more than a couple of needle widths higher than N (normally it runs a couple below) unless it is slogging up a hill, and that is with a rally plaque in front of the grille.

Whilst Clifton is correct in saying that if it isn't losing coolant or steaming it isn't overheating, a needle width or two short of the H is certainly higher than I would expect to see and certainly cause for investigation in my mind.

On a CNH gauge 194 degrees equates to about mid-way between N and H, with 180 being about N, making 210 degrees indeed close to H. However on Farenheit gauges 210 equates to being about mid-way between N and H, and H is 230.

It may be that your gauge is reading too high, either because the voltage stabiliser is faulty or not picking up a ground from its physical mounting, or the sender is faulty or the incorrect item. Because 180F is the standard thermostat for cars of your era, and they should read around N, if yours is reading near N with a 160 at 70 degrees it does indicate to me that the gauge is reading high.
Paul Hunt 2

RW, try running 60/40 or 70/30 water to anti-freeze and add some Red Line's Water Wetter, avaliable at your local parts store. In southern Ontario, we get alot of 90+ humid days and my B runs just over the "N" , mooooost of the time.

Bob 75B
Bob Klymciw

RW,
last year you cleaned up the radiator inside and outside and have not run into problems afterwards last year.
Are you sure the thermostate is working well? did you take it out and tested it in the kitchen?
Did you also clean the entire cooling systen, engine and heater? Could it be that the radiator has been contaminated meanwhile from deposits form the engine and cooling system?
There are cooling system cleaners offered that should be added to the coolant and then the car is driven as stated and the coolant then reneved after a flashing of the whole system with fresh water after it has cooled down.
Due to the working temperatures of the B-Series engine only destillated water should be used with additional anti freeze as only this mixture avoids fall out of chalk from the water and prevent oxidation too.
If you open the cooling system, risk a new gasket for the water pump too and remove it for a check.

Hope this helps

Ralph
Ralph

Going back to RWs radiator readings, whilst it is correct that the temperature should drop as you move down the rad, with no cooler spots anywhere, I'm wondering whether the temp at the bottom is *too* cool, implying a reduced coolant flow. I don't have an infra-red thermometer to check mine (Maplin's are supposed to be getting some for 14 quid, can't wait), can anyone else do a check on theirs?

Reduced flow could be a partially stuck thermostat (relatively easy to check, remove it altogether for a while, but not permanemtly without fitting a blanking sleeve or an old stat with the return spring removed), a weak pump (corroded impeller blades, and I do recall reading that an incorrect pump can be fitted to some engines which gives low flow), or blockages in the engine or rad. I don't think the rad is blocked if the temps across it are the same, and if the engine had blockages then I'd expect to get very hot spots which would boil the coolant close to them.
Paul Hunt 2

Is your timing right?
Your mixture isn't lean?
Your fan is correct, spinning the right direction, properly shrouded?
Thermostat is opening? Water is flowing? Heater works?

Then you'd better suspect the radiator in spite of the readings.

Is 165 degrees too cool at the bottom of the radiator? Not if he's running a 160 thermostat it ain't. I'd say that's downright warm. Seems to me there isn't enough heat being transferred out of the radiator.

Now. Radiators can fail in all kinds of ways, not always a clog causing localised cool spots - perhaps there's just an even layer of rust or scale coating all the insides of the tubes, which slows heat transfer across the board. It's like having a layer of insulation inside your, uh, radiator. Still enough heat transfer when it's 70 out, but not enough when it's 90. The rad hasn't really failed, but it's marginal, and given a hot day, well, you see the results. That's my theory.

So, if all the questions in the first paragraph can be answered 'yes' then my money is on the radiator. Yes, in spite of the absence of any cool spots on it. Get a good new 4-core radiator and you should see a big difference.

I know, the only way to test this theory is to spend lots of money. It isn't what you want to hear. Sorry. But there's never any harm in having a really solid radiator.
Sam

I also note thast you can see some coolant leaks, changing the hoses and the water pump, making sure you get the right one, would not be costly. Running rich should keep the engine cooler.
Stan Best

RW,

I agree with Stan that the appearance of coolant in the region of the water pump suggests a cause. I had my 69 off the road for close on a year with engine out and pump off. On reassembly that water pump had lost its seal and started to leak. Temperature needle behaved just as you describe.

Stan's point about hoses is also a good one. Age or poor quality parts can cause collapse of the bottom hose with significant affects on flow and temperature.

I also note your reference to 'Last year no more temperature problems' suggesting a past history of some issue here at least. Perhaps that is why the 160F thermostat is fitted?

FWIW my Leyland manual lists thermostats as:

normal 180F
hot climate 165F
cold climate 190F

I run a 180 in mine and we certainly see extended periods in spring through to autumn up in the 90 plus temperature region. My needle usually sits just on the N, climbing perhaps a width above under extra load (eg hills) and perhaps 3/4 of the way to the H when left sitting after switch-off. But then I've always thought our temperature ranges were normal, and marvelled at the abnormality of climate in other places around the world!

I also agree with Clifton that around 25% glycol anti-freeze/boil additive should be about maximum, and that it causes hotter running when in mixtures around the 50%. My drivers handbook suggests a 20% solution of ethylene glycol type anti-freeze (no mention of anti boil, but these are English cars!) for protection down to 16F (commencing freezing) with an absolute safe limit of -3F. A 25 % solution suggested for respective temperatures of 9F and -15F, 30% for 3F and -28F. I imagine current products to be as least as efficient as those of the time of the handbook.

It would be interesting to know the cause when you have it sorted RW.

Regards
Roger
Roger T

Sorry, I meant 'too hot' which is what a reduced coolant flow would give.
Paul Hunt 2

Sounds like the link is with the valve job. Do you have good compressions on all cylinders. If one or more cylinders are low on compresion the bang will be creating heat and no piston movement, hence the high temperatures.
buckslad

Paul Hunt wrote:

"Reduced flow could be a partially stuck thermostat (relatively easy to check, remove it altogether for a while, but not permanemtly without fitting a blanking sleeve or an old stat with the return spring removed)"

After visiting Bob Muenchasen's web site and reading his article on cooling ( [http://www.cibolas7.net/12299.html] ), I have been running a 180° thermostat AND a blanking sleeve. I had the car [69 B] out this past Saturday for a three hour drive in ambient temperatures of 95°F - and I had absolutley no overheating problems. Bob actually uses a 195° thermostat but I'm too chicken to go that far.

The blanking sleeve effectively causes the coolant to go straight from the engine to the radiator thus avoiding any bypassing to a side port in the cylinder head. By using the blanking sleeve, it does take a wee bit longer for the engine to warm up - but after that, I can see absolutely no negatives. My temp needle stabilizes about 2 needle widths past the "N" in the middle.
Tom Fisher

This thread was discussed between 14/06/2007 and 20/06/2007

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