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MG MGB Technical - Cooling Help

68 b stock, Having trouble with cooling. Relative new radiator recently flushed. I pulled the plug out on the right side of the engine. No fluid ran out. I hooked my air compressor an aplied up to 130 psi tto the engine without the theromostat. Still not fluid adn very few bubbles in the radiator. What could be blocking that severly. Also opend the heater valve no change. Any ideas? Thanks Larry
Larry

The drain plug blockage is very common. You have to drill down to it from the top, with the cylinder head off. I tried on mine, but was afraid I was drilling something that mattered so mine is still blocked.
You can try a chemical cooling system flush, or hydrochloric acid to remove the internal scale and rust. I would disconnect the heater from the engine and join the pipes together before using it though, as sometimes removing the internal scale can make it leak.
Martin Layton

I got mine unblocked when the engine was rebuilt. I added a anti-freeze and distilled water mix and one year later it was blocked again. I have opened 3 different MGB engines and all of them were dry under the plug.

Clifton
Clifton Gordon

this is straight from the book of chemical theory
personal practical experience nil.

Useful fact-phosphoric acid dissolves iron oxides (there are at least 3), but forms a dark purple thin pasivating layer on iron or steel and will NOT dissolve solid metal.
As a mad chemist, I personally would give it a go, but you are not me.
peter

Larry,
I have had this same problem year after year on my 1980 'B'. So far, I have been able to removed the engine plug and used a section of wire coat hanger to unplug the hole. There is usually a fair amount of silt that I remove and then suddenly the hole unplugs and water/antifreeze shots out like it was under great pressure. I then flush the system with a garden hose until it seems to run free. I put the plug back in a fill-up with distilled water, anti-freeze and a little "Water Wetter" and then do the same thing the next year.

Dave
Dave Kalp

What troubles are you having (apart from the plugged block drain) -- i.e. what are the symptoms? Are you sure you aren't chasing ghosts?

Cheers!
Rob Edwards

The plugged drain itself won't cause cooling problems. It's quite normal for the temp gauge to get up to mid-way between N and H in high ambient temperatures, and higher isn't a problem if it isn't steaming or losing coolant. So as Rob asks, what are the symptoms?
Paul Hunt 2

The guage gets about half way to te H and the engine begins to miss. I tried flushing with caustic soda. I don't have a problem with the phospheric acid idea and may try that. Has anyone taken the freez plug out to help clean the rust? I will probably try the hanger first. I appreciate the feed back. Thanks Larry
Larry

Running shouldn't be affected no matter how high the gauge gets, until it has boiled and you lose so much coolant that it siezes. There is something else wrong if you are getting a misfire. Is coolant dripping from the heater valve onto the distributor (take the cap off and look for condensation inside)? If that's OK there is some other temperature dependant problem with the ignition or carburation.

Ignition is easy to check by clipping a timing light onto each plug lead, if the flashes get erratic with the misfire then it is an ignition problem. Check the coil lead as well, and if that is OK it is the cap and/or rotor breaking down. If the coil lead gets erratic as well (it flashes at 4 times the rate of any coil lead so this can really only be seen at lower revs) then it is either the coil or the trigger. If the tach gets erratic as well then it is probably the trigger, but could also be coil or connections. When on 1 or 4 check the timing as well and see if it jitters more with the misfire. Also measure the dwell and see if that jitters with the misfire.

If plug lead flashes are smooth and steady with the misfire then it is either plugs or carburation.
Paul Hunt 2

Using acid to clear internal rust is not mad - it's actually done pretty often. If you can find phosphoric acid, knock yourself out. If not, Muriatic acid is cheap and readily available wherever janitorial supplies are sold and it works perfectly, dissolving oxides brilliantly - but you do have to rinse it out well, as it can and will attack the base metal if left in there long enough. (You can run it for a day or so, no problem) It's best to use it when the engine's out for a rebuild, as, well, it's acid and you know better than to get acid over your car.
Sam Good

Hi all,
I did it myself once. Using white vinegar inside of block gave me a pretty nice result. Head off, I Just removed the water pump , setup a blanck plate in place and filled the block with pure vinegar. I Left things during 2 weeks. After the cleaning stage with a high pressure water, I discovered nearly new condition external cylinders walls plus the bottom flushing hole operational.
Regards.
Renou

This thread was discussed between 19/08/2007 and 06/09/2007

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