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Loosing coolant

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BH Davis Avatar
Grosvenordale, CT &, Warren, VT, USA   USA
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1968 MG MGB GT "Primrose"
1973 MG MGB
This has happened twice now so I guess I need some help trying to figure out what is happening.

I'll drive the car about 20 miles on the highway in 80 degree weather. When I pull in my driveway at home I leave a trail of antifreeze drippings. The radiator is down to the plate about 1 1/2" below the cap. Everything around the overflow tube under the car is soaked in antifreeze. There is no visible sign of leakage from the radiator or the hoses and connections (although the tip of the bottom hose just behind the overflow tube has a small wet spot). The overflow tube appears to be the culprit.

When running on the highway at 60 to 65 in OD the temperature gauge stays at the right side of the N. However when I pull of the ramp and slow down it spikes up another 1/4" to the right........just below halfway between N and H.

The plan this weekend was to replace the 3 side freeze plugs, change the oil etc., retorque the head and manifold and then give it a fresh tuneup (timing/carbs). I would like to resolve the antifreeze loss issue at the same time if I can.

Engine:

Newly rebuilt 18v engine with just under 500 miles on it.
Recored radiator.
New temperature sensor.
New 160 degree thermostat (started with 180 degree but the car was running with the temp gauge well beyond N).
50/50 mix of antifreeze.
Timing set at 12 degrees BTDC at 1000 rpm.
Plugs are a very light reddish white......perhaps a touch lean to not overly.
A freeze plug blew out at 140 miles and has been temporarily replaced with with a Dorman rubber plug. New freeze plugs to go in this weekend.

Thanks,
BH

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rntanner Avatar
rntanner Roger N. Tanner (Disabled)
Oxnard, CA, USA   USA
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1970 MG MGB
1977 MG MGB
Yes/No?

Radiator sent to the radiator shop..both top and bottom tanks removed.....radiator core tubes mechanically cleaned....radiator soldered back together and pressure tested....If the answer is, "No". Do it.

If the answer is yes, it has already been done, have them leak check the radiator at the radiator shop again, with you watching.

All new coolant hoses from engine to radiator and engine to heater core?

Brand new water pump?



Roger N. Tanner
Professional Engineer, Retired

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BH Davis Avatar
Grosvenordale, CT &, Warren, VT, USA   USA
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1968 MG MGB GT "Primrose"
1973 MG MGB
No I didn't replace the water pump. Perhaps that should be done. However it is not the original pump and looked to be in good shape.....although I've had the car 9 years so it is at least that old.

The radiator was recored by a professional shop......long time in business. Hoses are about 5 years old and in good shape.

If it is coming out the overflow wouldn't the coolant have to be boiling or under very high pressure? The exit is above the water line.

BH



Edited 3 time(s). Last edit at 2014-08-20 07:52 PM by BH Davis.

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Baggy Dog Avatar
Baggy Dog Nick Harris
Brisbane, QLD, Australia   AUS
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Are you sure you have managed to get all the air out of the system, including the heater core?

Would be worth having another go at burping the system.

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Ogre1 Avatar
Ogre1 Allan Ogilvie
Melbourne Victoria, Australia   AUS
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1977 MG MGB "Greenb"
Run the car and look for bubbles in the rad. I am betting you have an over presurised cooling system. First check your cap then run the car with the cap off and watch for bubbles.

If you over heated when you popped out a freeze plug, you may have blown a head gasket. Combustion gases in the radiator can be tested by some rad shops but will cost. they can also pressurised the system and see if it holds pressure.

Cheers

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ohlord Avatar
ohlord Platinum Member Rob C
A tiny Island off the coast of Washington State, N.W., USA   USA
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1957 Land Rover Series I "EYEYIYI"
1957 Land Rover Series I "OVRLND"
1971 MG MGB
1971 MG MGB "Bedouin 2"    & more
The thermostat has nothing to do with how hot the temp is when running,only the temp at which the stat opens.
Replace it with a fail safe 180F stat.
Check what pressure your cap is rated.
make sure your fan blade is installed correctly
Replace the freeze plugs and do a leakdown test.

Per above you can test for combustion gas by a cheap test strip kit you can purchase at autozone etc.



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Edited 1 time(s). Last edit at 2014-08-20 07:22 PM by ohlord.

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BH Davis Avatar
Grosvenordale, CT &, Warren, VT, USA   USA
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1968 MG MGB GT "Primrose"
1973 MG MGB
Thanks everyone. Will work on your suggestions tomorrow.
BH

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72MG-racer Avatar
72MG-racer Lee P
Lexington, KY, USA   USA
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1978 MG MGB
Possible head gasket failure. If that happens you can over pressurize the coolant system and blow coolant out the overflow.

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rocannon Avatar
rocannon Gold Member rocannon L
Comanche County, OK, USA   USA
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1967 MG MGB GT "GT From Hell"
Radiator cap still good?



Pogo is right.
—————————————————————-
Nothing beside remains. Round the decay…. Boundless and bare
The lone and level sands stretch far away.

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BH Davis Avatar
Grosvenordale, CT &, Warren, VT, USA   USA
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1968 MG MGB GT "Primrose"
1973 MG MGB
If it is the head gasket will I be able to tell by looking at it?

BH

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MGBUK Avatar
MGBUK David C
Chesham, Bucks, UK   GBR
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1980 MG MGB GT "JAM"
if it is the head gasket, and depending on which way it has split, you might see a milky substance on the underside of the oil filler cap, which is the residue of oil mixing with antifreeze in the engine......

its actually the first thing i look for whenever i buy a car smiling smiley

also you can actually smell it sometimes too, when my gasket went on my merc w124 you could smell exhaust fumes in the coolant expansion bottle, and that was boiling the coolant - there is a tool you can get (5 gas analyzer i think) / go to a repair garage and check it, whereby they measure the level of combustion gases in the coolant, which is another good way to check

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BH Davis Avatar
Grosvenordale, CT &, Warren, VT, USA   USA
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1968 MG MGB GT "Primrose"
1973 MG MGB
As I mentioned at the start of this discussion this problem is on a newly rebuilt engine. At the time of the overflows it was at 400 miles with another hundred before the first oil change and torquing the head.

Well I retorqued the head and readjusted the valves this afternoon. Then I ran the engine with the heater turned on for a while. For the first time I saw a river like flow of coolant through the radiator. A highway ride afterward showed no problem.

I think this problem was likely a combination of some air in the system and the head being ready for the retorque. Hopefully it is resolved.

Thanks everyone.
BH

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BH Davis Avatar
Grosvenordale, CT &, Warren, VT, USA   USA
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1968 MG MGB GT "Primrose"
1973 MG MGB
Hopefully the coolant problem was resolved last night. I retorqued the head (500 miles on new engine so it was time). Then I adjusted the valves. Then I ran the engine for 15 minutes with the heater valve open.

I think this resolved 2 things: there may have been some leakage in the head gasket before the retorque and there may have been an air bubble due to my never running the engine with the heater valve open since the rebuild.

I took the car on the highway fora bout 20 miles and had no coolant issues at all although it wasn't as hot out as it had been. However when I opened the radiator cap I could see a river like flow of coolant and that was not the case before. It had been a sporadic flow with more of a foamy appearance.

Thank you to everyone for the guidance in tracking this down. Hopefully the problem has been resolved.

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Tiger05 Avatar
Tiger05 Charles Ward
Mechanicsville, VA, USA   USA
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1980 MG MGB
* Losing Coolant Loosing is to set free. To turn loose of. I suppose that could be correct but not what I think you were trying to say.


Good luck with the issue.





Charles

MG



"Those unwilling to fight for their freedom will be enslaved by those willing to kill for power. Absorb it in every fiber of your being, for it is the nature of man and the men who govern. De Opresso Liber!!"

"Silver... or lead." Ravinglawyer13



"A cleaved head no longer plots." Norse proverb.

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ddubois Avatar
ddubois Dave DuBois (RIP)
Bremerton, WA, USA   USA
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BH - You could have a non problem. If you filled the radiator clear to the top, it is normal for the cooling system to expel excess coolant after the engine comes to normal driving temperature and is then shut down. after it does that, if the coolant expelled is not replaced, nor more (or very little) will be expelled from then on. If this is really a concern, you can install a coolant recovery system to catch the expelled coolant and return it to the radiator when the system cools. See the article Expansion Tanks, Coolant Recovery Systems and How The Cooling System Works in the Other Tech Articles section of my Homepage, linked in the signature block below.
Cheers,



Dave DuBois
1953 MGTD
1966 MGB
http://homepages.donobi.net/sufuelpumps/

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