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overheating in cold Canada

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dezwartj Avatar
dezwartj Josh de Zwart
Calgary, Canada   CAN
I am slowly getting to the stage to throw my hands in the air. Last summer my '77 "B" got stuck on the highway in rubber bumper to rubber bumper traffic. It started to overheat and steam was coming out of my front grill. I finally managed to get off the highway and into a residential area where a helpful person gave me several gallons of water. It turned out that the heat switch in the radiator gave the ghost and therefore no working electrical fans. Since then it keeps on overheating and I hardly drive at anymore. What I did this winter to rectify the problem was : I had the radiator steamed out and tested. Installed a new heat sensor in the engine block, Installed a new thermostat, and the switch in the radiator. Unbolted the water pump to check its condition. It was like new, so I put it back again. Installed new belt. However, when I drove it around the block today, the temperature meter very quickly approaches the red area again (drove only about 3 Km). The new radiator fluid keeps at level, and there is no signs of water in my engine oil nor any leakage.
Anyone have advice on what the solution to this overheating problem might be??? I didn't pull the cylinder head yet.

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rustynut17 Jerry O
Almont, Mich, USA   USA
Did those fans ever come on ?... maybe not getting power to the fans ?

dezwartj Avatar
dezwartj Josh de Zwart
Calgary, Canada   CAN
to be on the safe side, I wired the electric fans to a temporary switch inside the MG -B. to ensure they are working. And yes, I checked several times, they are working pretty good (i can hear them when idling)

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rustynut17 Jerry O
Almont, Mich, USA   USA
Thermostat in correctly?... hows that radiator cap ?

lewisrn Avatar
lewisrn Gold Member Bob L
Danville, IN, USA   USA
1980 MG MGB "The "B"
Get an infrared thermometer and check the temp at the top and bottom of the radiator and at the engine thermostat.

https://www.harborfreight.com/non-contact-infrared-thermometer-with-laser-targeting-69465.html



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Edited 1 time(s). Last edit at 2018-04-16 11:53 AM by lewisrn.

gofastandfalldown Avatar
gofastandfalldown Glen Horne
Edmonton, AB, Canada   CAN
1970 MG MGB MkII "Miss Pandora Moneypit"
With the weather forecast for Calgary tonight, you won't have to worry about it for awhile. winking smiley

I'd be looking again at that thermostat. Installed backwards or just plain faulty?

Also, is it possible that the temperature gauge sensor is faulty after being thermally stressed? Other than the gauge reading, what other indication of overheating do you have?



Edited 1 time(s). Last edit at 2018-04-15 09:06 PM by gofastandfalldown.

Cruisedon66 Avatar
Cruisedon66 Pete W
St. Louis, MO, USA   USA
1976 MG MGB
Engine oil will loose it's properties once it's been overheated. Change the oil.
Possibly enging internals have been warped from overheating too.
Does the engine still spin briskly when starting?
Does it sound even at idle?
Check the radiator cap seal too.

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Steve64B Avatar
Steve64B Steve Opitz
Phoenix, AZ, USA   USA
1966 MG MGB
I just did a quick check of Calgary's weather... 35* F, and you're overheating?!? Very real possibility that you damaged the head gasket or worse cracked the head.

kmartin Avatar
kmartin Gold Member Ken Martin
Phoenix, AZ, USA   USA
1953 MG TD MkII "Baby"
1959 Austin-Healey 3000
1967 MG MGB GT "Blue Bell"
Something to check, a friend in our car club was fighting overheating and he did about everything you did. In the end, he checked his fans and they were blowing the wrong direction, switched the wires and everything was right in the world again.
Ken

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ozieagle Avatar
ozieagle Gold Member Herb Adler
Geelong Victoria, Australia   AUS
1958 Wolseley 1500 "Wooly"
1966 MG MGB "Bl**dy B"
Maybe you warped the head, when it over heated.

Herb



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dezwartj Avatar
dezwartj Josh de Zwart
Calgary, Canada   CAN
Thanks all for the advice. I will lift the head and check. There is no radiator cap on a 77 MG-B and the thermostat is definitely installed the proper way. Will check in a pan with boiling water to see if it opens...

simenon Toni Kavcic
Kocevje, Slovenia   SVN
1966 MG MGB
I assume that you still have original radiator so would suggest to buy a new one. You can’t imagine how many problems disappear with that. If is radiator blocked with sludge steaming won’t help and pressure test will show that it does not leak. But this is not problem you are describing. So check few points before.
1. Is engine really overheating or only gauge showing that? If so temperature should affect also oil. Does oil pressure drop when engine overheats?
2. There is no radiator cap but you have cap on expansion tank. It pressurize cooling system. It means that water wont boil at 100 deg Celsius (212 deg Fahrenheit) but much higher (depending on rating of pressure cap). Check both rubber gaskets on cap!
3. Check thermostat in pot of water. Pay attention how it opens. It should open gradually not jump from close to open. And when you will have it out make on flange small 3 mm (1/8) hole. It will help relief trapped air.
4. When you are already boiling water, check also fan switch.
5. Maybe this sound silly but you won’t believe – when you turn pulley on water pump does impeller also rotate?
6. As Martin suggested check in which direction is fan blowing.

If all above is OK then you are ready for new radiator. And leave head on block - it is huge chunk of iron and it won’t deform so easy (as aluminium).

bencii Ben Colpitts
Mansfield, OH, USA   USA
1966 MG MGB
I wouldn't be pulling the head just yet. 3 km (less than 2 miles) seems way too fast for a car to over heat unless you are letting it idle for a long period before starting out. I would first start with a test of the temperature sending unit and the temperature gauge. Here is a procedure I found that was written up for a GM car, but manufacturer should not matter. Ignore the color of the wire in the description below.

Temperature gauge troubleshooting begins with isolating the problem either to the gauge, sending unit, fuse or wiring. As with any electrical troubleshooting it is best to check all wiring connections are clean, tight and free of corrosion.

The following process must be preformed with the ignition key turned to the “on” position. The first place to start is at the temperature-sending unit. Remove the wire from the temperature-sending unit located on the engine (typically a dark green wire). Then connect the wire to a good ground. You can do this by using a jumper wire. Check the gauge, if the needle points to “Hot”, replace the sending unit. If the needle does not move, remove the same dark green wire from back of the gauge and connect a jumper from the terminal on the back of the gauge to a good ground. Check the gauge if the needle moves toward “Hot”, the wire from the gauge to the sending unit has an open or bad connection. If it does not move, connect a test light by grounding one end to a good known ground and the other end to positive side of the gauge (typically a pink wire). If it does not illuminate, ensure the gas gauge fuse is good. If the fuse is good, connect a jumper wire between the ignition switch and the positive side of the gauge. If the gauge now works, replace the defective wiring between the gauge and the ignition switch. If the test light illuminates there is 12 volts present, replace the temperature gauge.

Could you confirm that your fuel gauge is working properly and accurately? If not or unsure test the voltage stablizer.
You didn't mention replacing any hoses? How old are they and what is their condition? Is the upper hose hotter than the lower hose? Does running the heater lower the temp?

Oshawa Avatar
Oshawa Dan Deute
Millbrook, ON, Canada   CAN
1976 MG MGB
Another possibility that may be occuring is that you have an airlock in the cooling system. Mgb's can get this if the cooling system empties and then you refill it. Over heating will show up very quickly because there is no water circulation. Open the filler bolt on top of the thermostat housing and top up the system through it. Also make sure the heater is on high when filling. Another possibility is that one of the rad hoses are collapsing internally.

Cruisedon66 Avatar
Cruisedon66 Pete W
St. Louis, MO, USA   USA
1976 MG MGB
http://www.mgb-register.org/electrical-tech-tips/

TEMPERATURE GAUGE DOES NOT WORK.
Probable cause is a defective sender unit. Check as follows: Remove the Green/Blue wire from the sender unit in the cylinder head. Connect one end of your test light to the terminal on this wire, the other end to ground. Switch on the ignition. The gauge should slowly climb to hot and the test light should glow. If the gauge does register, the sender unit is bad. If the gauge does not read, check for loose wires. If none are found the gauge needs replacing.

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