Moss Motors, Ltd

Hi all.

My 66B tends to lose water after a 30-50 mile drive. When I park, the over flow spills water on the driveway.  The car runs b/w 160 and 195 degrees.  I have had the radiator serviced, water new pump, 7 lb cap and I believe a 160' thermostat.  What temp do these cars typically run at and what can I do to prevent the lose of coolant?  Is this typical?

 

Thanks for your help.

 

Matt

Matt,

If you don't have an overflow recovery system and you fill the radiator up you will always lose water. The water expands and pushes past the cap. It is unstoppable. A 7 pound cap is kind of low. You can go to a twelve with no real problem, but do consider adding a recovery system with a recovery style cap so that the expanding coolant will be drawn back into the system once the engine cools. This way, the system is always completely full. Also, you won't be leaving antifreeze on the pavement. The 160 thermostat may open sooner, but it won't actually lower the temperature at which your car will run. That is determined by many other conditions. The actual purpose of the thermostat is to warm your car up more quickly, and a lower temperature thermostat may actually delay that. It depends on your local climate. It is a common misconception that the purpose of a thermostat is to keep your car cool by opening at the right time. It's function is, as stated, to warm your engine up and to then take itself out of play(depending on ambient temp.) except to act as a restricted opening in the system to cause the coolant to flow at the most efficient rate.

Oh yeah, your car is running at typical temperatures, except that the lower one you mention is a tad low for good wear and efficiency. I'd try a 180 thermostat.

 

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Just to echo motorbill's comment, this is normal. I was surprised that my system overflowed after refilling the first time - and of course being new to this, I really tried to make sure it was full to the brim... However, if one thinks about it, this overspill is inevitable.

 Cheers,

Ed

 

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I want my MGB

Thanks Bill for clarifying this issue.  If you do not mind, I have anothe question for you.  After running the car on the road at full running temp. the idle drops from about 1200 down below 1000 at the stop light and then when I pess the clutch is almost dies.  Do you think I have a carb or timing problem, or other issue?

 

thank you,

Matt

Matt,

The idle speed change after warm-up is pretty normal. Oil viscosity changes, running clearances change, and even the mixture will respond to different temperatures of operation. Generally, we warm a car up thoroughly and then tune it. An early B, depending on its condition, is one we try to get to idle at just under a thousand RPM or so, consistent with smoothness.

What worries me more in the case of your car is that when you depress the clutch the engine almost stalls. Now, there are many possibilities here, but if the mixture and timing are correct, and the carburetters are in good repair, this should not happen. I'm wondering how long you've had this car and what you know about its mechanical history. When the idle drops dramatically upon declutching, as in your case, it can indicate that there is an awful lot of mechanical drag being introduced. Possible causes are a bad release bearing worn down into the cast iron holder, or a bad input shaft bearing or spigot bearing. Is there any noise or sound difference accompaning this drop in RPM? Let's not panic. It may be nothing of consequence. But, let's look into it.

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Aloha Ed,

I had the same experience you did.  I just purchased a 66 B.  Worse than the radiator experience was when I filled up the gas tank all the way and parked the car in front of my house in the hot sun.  I learned my lesson on that one...gas leaking out at the gas cap because of expansion... 

Aloha,

RobMGB66

RobMGB66

Funny you should mention filling the tank. I haven't had it overflow, but the location and orientation of the filler neck makes this a tricky task on the 'B. This is aside from the dificulty of facing up to the fact that one needss to shell out for petrol in the first place. Add to this the modern petrol pumps with a vapour recovery system - you're practically holding them upside-down to convince them to run...

 Ed

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I want my MGB

A recovery tank is a good idea if you don't want to deal with issue. We are in Southern California and in the summer time we have to fill water after every drive. Its bad because the driveway can get nasty if you have coolant leaking and the smell is no picnic either.

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Cars and motorcycle video collection

realizing this post is somewhat old - thought I'd throw in a different spin.  So, if I have a '76 B (w/cat, non-od) and it does not have an overflow tank installed, where would you mount it?  I actually have one laying in the garage off a different B (thought i could put it on my Sprite, but don't need to).

There's no obvious spot in the engine compartment where one might have been before (at least, not one i've seen yet).  All i have now is the small rubber hose that connects just below the radiator cap and hangs down along the drivers side of the radiator to the floor.  Is that the only connection hose to the overflow tank if i install the tank?

thanks in advance,

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Lou
'76 MGB MKIII

Lou,

Yes, that is the only connection you'll need. The only consideration for mounting the tank is that it should be lower than the top tank of the radiator. If the tank you have is from a different B, it may have a pressure cap on it. You don't want this. The system should have only one pressure cap, and if there is one on the radiator itself, just put a plain cap on the overflow. If the tank you have is one of the rounded metal ones, I wouldn't be too crazy about using it. Most auto parts stores have generic overflow systems for sale cheap. That's what I'd use for its greater capacity and the fact that you can see through it to determine if you have adequate fluid. Make sure the cap on the radiator is the recovery type, with a sprung valve to allow the coolant to flow back into the system when the engine cools and the coolant "shrinks".

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

I had the same problem, t was embarrassing to piss on the ground where ever I parked. Then I found out there are two different length of radiator filler necks, 1" & 3/4". Either 4 lb or 7 lb cap will fit  but the 3/4" cap will not seal properly if you had a 1" neck,  hence the overflow spill. 

For more info on this subject, check out mgaguru's article at http://mgaguru.com/mgtech/cooling/cool_101.htm 

For information on installing a coolant recovery system and how they work, see the article, Expansion Tanks, Coolant Recovery Systems, and How the Cooling System Works in the Other Tech Articles on my web site at: http://homepages.donobi.net/sufuelpumps/

Cheers,

Dave

 

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Cheers,
Dave
http://homepages.donobi.net/sufuelpumps/