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MG MGB Technical - Warming up.... it doesn't!

Now that my B has become my daily runner, do I have a problem with my car as it does not seem to want to get more than quarter of an inch away from the white area of the temperature gauge that indicates cold!

A colleague has suggested blank off half the radiator, however I've heard previously that this can cause hotspots.

I have taken out the scoop that brings air from under the oil cooler.

Oh its a 1975 rubber bumper Jubilee BGT.

Any advice appreciated.

Andrew.
A I McGee

Andrew,
my 1975 B just has 70 deg. cent. water temp when it is
running with temp. at the freezing point outside.
If you have an electric fan installed, you can cover the air intake at the slam panel. This will return the normal temp. to the engine in winter time.

Checked it out and fabricated a pice of thin plywood therfore. It can easyly be fitted with rubber shock cable and does not cover the area where the horns are built in.
By the way, if you use the B as a daily driver, have a oil temp thermostat fitted to your car!
Ralph
Ralph

A thermostat stuck open will slow the time it takes the engine to warm up but it will get warm eventually. This cold spell could be highlighting the effect, but from my experience this sounds like a readings issue, either with the gauge or sender misreporting. I'd start by dropping a thermometer in the top of the radiator after a good run. If it's around 75*C-85*C (you'll need a cooking thermometer) the engine is at normal temperature. The less technical test is to put your hand on the radiator - it will feel about as hot as a mug of coffee.
Steve Postins

My car showed the same symptom just before the temperature sender failed - would not show more than 1/8-1/4 inch away from "C" after an hour at highway speed. Changed to a new sender and gauge went to "N".
wllie L

I agree that it's just as likely to be the sending unit. Mine continually ran halfway between C and N. I broke the blade off the sending unit while replacing the alternator, so I had to replace it. Now with the new sending unit , the gauge reads just above N. I'm sure the actual temperature hasn't changed.
Dan

Andrew,

As a '75 UK spec car I think your temperature gauge will be driven by a capilary tube with a spring wound around it. This will not fail for some of the reaons mentioned by those with US spec car which had electric senders long before '75.

As Steve Postings says you need to use a cooking thermometer to check your gauge is reading correctly. This test can only be carried out if the thermostat is open.

The thermostat can be tested by puting it in a pan of water on the cooker and seeing that it opens and closes properly. You can use a cooking thermometer to check that it is doing this at the specified temperature. It opens gradually.
DJ Witham

Or just put a piece of cardboard blocking half of the radiator until the cold spell passes. We use ours as a daily driver and when the temps got above 35 degrees farenheit, I just removed it. Car heats up quicker and stays warmer and the carbs are happy with the warmer temps. Simple fix works really nice and as far as hot spots go, the coolant is always flowing thru the radiator.
Mwhitt

Andrew--A cooling system that can keep a car cool enough in the summer can over cool in the winter so the thermostat not only hastens warming the motor up, it limits flow on cold days to maintain the proper temperature. Maintaining the correct temperature keeps the oil at the optimum viscosity to limit wear. Thermostats are cheap so that’s a good place to start. As stated by others the oil cooler is not controlled by a thermostat and although they are available as aftermarket parts they are not so cheap, but normally are not that big a problem. You could try blocking the flow of air to the oil cooler rather than the radiator to see if that’s enough to solve your problem. As others said, the gauge or the sender could be giving you false readings and that could be true of dirty connections and bad wires. Still, other than checking the connections, the thermostat is the best place to start.

Steve--The reason radiators are kept under pressure is to allow them run hotter than the boiling point of water. Often you can release the pressure cap and the coolant will start to boil (at least around here). 75-85C (167-185F) sounds a little low for the best oil viscosity and proper fuel atomization. If that works well for you then go with it, but I would not suggest touching a hot radiator to anyone that doesn’t like the smell of burnt flesh. That’s a mighty hot mug of coffee!
George Champion

Thanks for your help, I'll investigate the thermostat and move on from there.

As it's a UK car the temperature gauge is controlled by the capilliary tube and I had heard these were a lot more reliable than the electric operated ones. Have I heard incorrectly?

But I would imagine that it is running cool as there is absolutley no heat coming out of the heater... or is that another one of the mysteries of a B.

I'm more used to midgets, but I am learning fast.

Thanks.

Andrew.
A I McGee

There is a similar thread in the MGA section. As I mentioned there, I too have an over cooling problem in winter. Mine is a '74 BGT. I had a Midget that over-cooled as well. Mine only solution was to cover the radiator. On the B, I cover the oil cooler for winter as well.
Kemper

George - point taken but those are the actual temperatures I measured on my GT and Roadster one summer when I went through the same fault finding - the rad's OK to test by touch but the coolant doesn't taste as good as my coffee.
Steve Postins

Andrew—No heat out of the heater probable means the car is running cold and that could be because a previous owner removed the thermostat (or it’s stuck open). Another possibility is the coolant level is too low to cycle through and that can also give false readings on a temperature gauge, but the car would over heat in an obvious way.

With fewer things to go wrong it makes sense the mechanical gauge would be more reliable. So why would they use a different system for some cars? I noticed the electric oil pressure gauge they called a safety gauge. It could be there was some law requiring safer gauges in some markets. As odd as it sounds it might have been cheaper to wire gauges for left hand drive cars rather than use different capillary tubes. Generally the only reasons a car company will change something is the law requires it or it’s cheaper to produce.

Steve—That’s funny. Personally, I dislike coffee, but one time I was under a car changing a radiator hose I got a face full of coolant and I liked it. It was sweet and taste like fruit juice. It’s no wonder people are encouraged to clean up spills so animals don’t lap it up.

Disclaimer time: Even if I prefer the taste of coolant to coffee, I recommend coffee over coolant for consumption. While I’m at it, taste aside, pouring coolant on your face is not recommended either. Even it it’s sub-boiling coffee temperature or cold as in my case, you will come out embarrassed and looking like a transient.
George Champion

Quick note....

After a five mile journey to work this morning I put our Latte Thermometre (but don't tell my colleagues!) into the radiator filler neck. It read 40 degrees C, so not that warm.

Average external temperature is around the 2 degree mark.

So the thermostat will be investigated, but is is worth blanking off the coolers anyway.

Andrew.
A I McGee

I'd suspect that the engine wouldn't get warm enough over five miles on a cold morning for the thermostat to open fully, so the low reading in the radiator could make sense. However, the water circulating the block should get hot in that time and that's what the gauge measures, so asssuming the gauge is good (has it ever read normally?), it could well be that the thermosatat is stuck open. Might be a cheap fix. That said, if your commute is only five miles I'd certainly blank off the radiator and oil cooler to help the oil get up to temperature. And by the was....latte thermometer? What ever happened to Yorkshire tea!
Steve Postins

Ah... Yorkshire Tea!

Yes we do partake of the occasional cuppa, however we were all swayed when we designed the branding and interior styling of a chain of coffee shops. Real coffee, you can't beat it.

So the when we finished the project I surprised everyone in the studio with a bean to cup machine and it has never "bean" the same!

Same thread are almost as many references to coffee!.

A.
A I McGee

There is a lot of cast iron to warm up in a B series engine. In the winter I block off an area about 9" by 6" with a pice of cardboard and this seems to let the thermostat regain control. It has been mentioned that it is cooling from other areas such as the sump which is causing the thermostat to lose control and the blanking just gets the airflow/heat loss back in balance. The thermostat is cheap and easy to swap.
Stan Best

So in this months Classic and Sportscar they advocate using a radiator blind on the B if used as an all year round car.

Will fit one tomorrow and lets see how it goes from there.....

Andrew.
A I McGee

I have fitted a blank plate measuring 3 inches high by the full width across the front face of the radiator at the base. The temperature gauge now reads at half way between the cold zone and the N.

Tomorrow I'll fit one at 5 inches high and see how we go with that.

A.
A I McGee

"It has been mentioned that it is cooling from other areas such as the sump ..."

Sump and surface cooling of the block from icy air blowing in through the radiator. That is what a radiator blind does - blocks air from passing into the engine compartment. Until the thermostat opens, which is only when the engine gets up to temp, there is only cold coolant in the radiator, which the blind has very little effect on.

But on my V8 and roadster on near freezing runs (although the latter not as a daily driver) whilst the temp needle *is* lower in winter it is only marginally lower, and that with the heater on.
Paul Hunt 2

Andrew,
My experience mirrors Paul's. In sub-freezing weather, my B roadster has no trouble coming up to operating temp without a radiator blind. It very much sounds as if your thermostat is bad. For no more than they cost, replace yours. It's much better to repair a fault than trying quasi-effective workarounds....

An aside: On advice I found on the internet, I drilled a 1/8" hole in the flange of a thermostat, because I was lead to believe it needed one. I was amazed to find that that little 1/8" hole was enough to prevent the engine from ever reaching normal temperature on a cold day ("ever" defined as slightly more than 10 miles, with about 5 of those at 70-75 mph). The thermostat tested fine in the "pot of hot water" test. I replaced it with one sans hole and it heats up normally....
Rob Edwards

Thanks guys, the car did seem to warm up quicker than normal on my short run with the blanking section, but Pauls comment makes perfect sense.

I didn't have time to swap the thermostat last weekend as I was busily tidying out the 4x4 and caravan before they were sold. So this weekend and at the risk of jeopardising the usability of the B, I'll change the stat.

Crossed fingers as the last time I swapped one I snapped the stud in the head and the only way I could get it sorted was for the head to be removed and taken to a local engineering shop.

The three nusts have been soaked with WD40 for the last three nights.....

Andrew.
A I McGee

Good luck.

I just changed mine last night. The three nuts came off nicely but the housing got stuck on one of the studs. No manner of heat; tapping, lifting; smashing would make it budge. After two hours of using various methods (including having soaked the studs overnight in PB Blaster) of removal, out came the cold chisel. Broke the housing in three pieces. Thankfully the studs were alright and cleaned up nicely.

Frankly I was more afraid of breaking the stud as I already had an extra housing on standby.

luis
Luigi

Some thermostats have a 'jiggler' valve in the main flange which is designed to let air through for bleeding, but block the passage of coolant (the bobble in the valve floats up in coolant to block the hole) until the main part opens. I can imagine that even a small clear hole in the flange would affect warming-up in cold weather. With a stuck housing you can try putting two nuts on each stud and turning or removing each stud to free the crud that occurs between steel studs and alloy housings.
Paul Hunt 2

Paul

you have just described what happened when the stud sheared in the head, this is one little job that I do not look forward.

Andrew
A I McGee

Well, you wiggle the stud back and fore, and it it feels like the stud is shearing and not unscrewing you leave it alone and move to plan B!
Paul Hunt 2

Andrew,
Quickly change to a 190 degree thermostat.
I live in Toronto and even in temps at 20F,or -5C, my car warms up. In the summer I change it back to a 165 F. If this doesn't work then check your heater. This, to me, is the quickest way to get to the problem. Changing the thermostat is easy. Good luck.
S. Hepburn

Why do you change back to a 165? I live in North Carolina, where the standard daily weather forecast from June to September is "Upper 90s with a chance of afternoon thunderstorms" and I run a 195F year-round. Running an engine too cold causes loss of power, reduced efficiency, and accelerated wear.

According to the late great Smokey Yunick, in his book "Power Secrets", running at 180F vs 220F reduces output by 2 to 3%. That's 2 to 3 HP for us!

A lot of folks mistakenly believe that a cooler thermostat will prevent an engine from overheating. However, a thermostat can only control the MINIMUM operating temperature. If the thermostat is open and the engine starts to run too cold, the thermostat can close prevent the water from getting to the radiator, which makes the engine heat up. If the thermostat is open and the engine starts to run too hot, there's nothing the thermostat can do -- it's already open. Thus, if your engine is going to overheat, it will do it regardless of what temperature thermostat is installed.

As I said, I run a 195F tstat, along with a 16 psi cap and a 50/50 mix of AF and water. My car has never overheated. With that combination, it shouldn't overheat until at least 265F.

HTH!
Rob Edwards

The reason stats used be changed between winter and summer was because there is far more heat lost from surface cooling of the block and sump in winter than summer, as well as the extra cooling provided by the heater. This causes lower than normal internal engine temperatures which the higher temp stat compensates for. In summer with a 'winter' stat you may find that the internal temperature of the engine is higher than it should be, even though the temp gauge might show the usual reading. I've never had any problems with standard stats in temps from 10 degrees below to over 90.

Other than that I agree with Rob. People get paranoid when the gauge gets a couple of needle widths above normal, but that is still 'normal' for that type of cooling system. Modern cars isolate the temp gauge from the cooling system with the ECU so it doesn't show the normal variations, even with electric fans switching on and off. This makes the driver of an MGB even more paranoid than they were in the 70s. I've seen my V8 on the verge of going into the red, and apart from running a bit roughly it was fine. If it isn't losing coolant or steaming it isn't overheating. Which has rather got away from the original topic.
Paul Hunt 2

Paul, don't worry about it getting away from the original topic as I am learning plenty from the ongoing posts.

I am now a little confused as to which thermostat I should get to replace the one that is currently in. I haven't had chance to look at the fitted one yet as I though for the sake of a gasket and the cost of a new one I'd just replace it anyway. Then I know what I am dealing with.

Andrew.
A I McGee

Well, Clausager sez the 82 was standard, then changed to 74 to increase hot oil pressures (another gauge to worry about), but subsequently changed back to 82, possibly when the oil cooler became standard. That is probably the best all-rounder for the UK.
Paul Hunt 2

I think part of the reason that older cars tended to be fitted with cooler tstats is that the oils of the day were fairly heat intolerant and would coke at relatively low temperatures. Modern oils are much better in this regard.

Just to muddy the waters a little, Peter Burgess, in his book "How to Power Tune MGB 4-Cylinder Engines," says that "The ideal 'stat is 88 degrees Celcius (190F)." And, as I mentioned before, I use a 195ºF tstat year-round with good results. The needle stays between just right of 'N' to just left of 'H', but the engine has never overheated. As Paul says, people get too concerned about temp readings. "Normal" isn't a point on the gauge, but rather a range. Dead on 'C' is too cold, dead on 'H' is too hot, and 'N' is everything between (with the hotter end to be preferred).

All this assumes of course that your cooling system is in good repair. If it's not, it needs to be fixed...

BTW -- if you need a gasket, go to my website, click "Free Stuff", print out the template, and trace it onto some gasket paper.

HTH!
Rob Edwards

This thread was discussed between 02/02/2006 and 12/02/2006

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