MGB 63 MGB Overheating Help!!

[Philsmgb]

Complete rebuild on the vehicle new radiator new thermostat.
Car overheats very quickly anyone have any suggestions what may be going on. I did notice rust in the new coolant..

 

[jessebogan]

If it overheats quickly, I would suspect the thermostat. Is the top radiator hose hot when the car is hot? Is the rad getting hot? What temperature thermostat did you install? It is easy to check a tstat with a pot of water on the stove, a candy thermometer, and a piece of wire to hang the thermostat on. See that it opens at all, and if so what temp does it start to open, and what temp it is fully open.

 

[Philsmgb]

seems as though the radiator stays cool yet the block is getting very very hot. Tested the them and it works as it should. When Idling it takes a while to get hot with a load gets very very hot in about three to four miles

 

[Deleted member 3577]

What does your gage say?

 

[Philsmgb]

pegged at 220

 

[Deleted member 3577]

Yipes......

I have never heard of an air bubble forming in MG engine.

I'd just throw in a blanking sleeve and try it again. (Moss #434-135)

Might be a good time to borrow/buy one of those nifty little infrared-laser gun thingies. (you'll love it)

(The head gasket is on there correctly....Right?)
(does it start fine......ie.not too lean)

 

[Philsmgb]

Head gasket should be on fine runs great till it gets hot then it starts to cut out and run pretty rough. I pulled the therm and tried to run it without and it still gets very hot. Necer really understood what the blanking plate was for:}

 

[Steve_S]

You sure the water pump is the correct type and functioning properly?

 

[David_DuBois]

Phil - If the radiator is not getting hot along with the engne, then something is stopping the flow of coolant throughthe radiator. Did sombody leave a shop rag in one of the radiator ports? don't rool your eyes, that has happened all too often, someone will stuff a rag into one of the ports to keep junk out of it and then forget and leave it in there. What about your water pump, is the impeller perhaps not turning with the shaft? Good luck - Dave

 

[Deleted member 3577]

I am getting pretty darn curious now......

I take it you are still "running in" the engine?

 

[jlaird]

I agree, it surely sounds like water is not circulating through the radiator. Think I would first remove the therostat and see if that changes things. I mean blanking plate or no blanking plate remove it for a test.

 

[Steve P.]

Hummmm...since the engine was just rebuilt, is there a
chance that you left a rag inside? Don't laugh, I've found rags in two engines. Both were wrapped up in the water pump.
I know when I have an engine apart I'll plug all open
holes with rags to keep crud out.

If thats not it, I'd suggest using a flushing compound
to flush the whole cooling system including the radiator.
I'll be doing the same thing on my MGB-GT this week.

 

[jlaird]

Guess you could always remove the radiator hose from the pump and crank it and see if water is pumping. Stand back.

 

[maynard]

The first thing I would do at this point is a compression test. You said the car overheats quickly, but din't give a time. Is it five minutes or fifteen? A bad head gasket could cause rapid overheating.

If the test comes out OK, try running it without the thermostat. If the stat is defective or installed backwards, you will have overheating.

Check the hoses when the car is running. Does the lower hose collapse when the engine is reved?

 

[PAUL161]

If the engine is hot and the rad is cool then there is a restriction in the cooling system. Take all the hoses off and check for a blockage. If you don't find one, then pull the pump and check for blockage in there. Make sure the impeller is tight on the shaft. Is the thermostat new? Check it in a pan of hot water to see if it opens. /ubbthreads/images/graemlins/cheers.gif PJ

 

[David_DuBois]

Maynard suggested something that is as common as a rag in a coolant port or more so, a thermostat that is installed upside down. Since that is the easiest thing to check for, I'd start there. good luck,

 

[Guinn]

If it were mine I would first see if water was being pumped TO the radiator, by pulling the upper hose off and running the engine.

If no water or very little is pumped, check the pump. If the pump is good, try to find that rag or whatever is limiting the flow, maybe the thermostat, as the problem would be in the engine.

If you get a good flow TO the radiator, I would check the condition of the hoses. One might be totally collapsed.
If the hoses are good I would consider pulling the radiator and having it cleaned and pressure checked.

Do the easy and cheap things first!

Guinn

 

[jlaird]

/ubbthreads/images/graemlins/lol.gif /ubbthreads/images/graemlins/lol.gif /ubbthreads/images/graemlins/thumbsup.gif

 

[tony barnhill]

[ QUOTE ]
Complete rebuild on the vehicle

[/ QUOTE ]

Did they flush the engine & head thoroughly after doing the machine work?

If no machine work was done prior to the rebuild, did you back flush the engine?

[ QUOTE ]
I have never heard of an air bubble forming in MG engine.

[/ QUOTE ]

The later ones will develop them - that's why you 'burp' them at the bolt on the thermostat cover.