First off, does anyone know the thread of the coolant drain plug on the engine block?

And second, is the plug accessible from under the car? I felt for it from the top, but it appears to be just below the exhaust manifold heat shield.

I've recently acquired a 2004 Cooper and want to add a water temperature gauge. The block drain plug seems to be a good location for the temperature sender.

Thanks in advance for your help!

 

I can't really help you with the thread specs. I've been trying to find that drain (off and on) for the past few years. The service manual says nothing of an engine block drain. If it's below the heat shield, it's probably inaccessible from under the car.

 

Thanks for the reply. The plug does exist; it's pictured in the Bentley manual in the Engine section. It's also visible in this picture of a Cooper S engine:

http://www.in2guitar.com/mini/enginerear.jpg

ETK lists the part number for the plug, but unlike the majority of fasteners in the catalog, it does not list the thread spec. I will probably just go up to the local dealer, get a plug out of their inventory, and measure the thread myself.

 

technically it is accesible from under the car however with the starter on the car it is nearly impossible to get to. and if you can it will probablly be a real pain in the but.

 

The bolt is 14mm X 1.5

 

Thanks!

Next question - is it safe to thread a brass temperature sender into a cast iron block? Will galvanic corrosion occur when these two dissimilar metals come into contact with one another?

 

No problem threading the brass adaptor into the block. The antifreeze contains anticorrosion additives to protect against damage, besides, most stock thermal sensors are often fashioned out of brass.

Remember, the engine is made with an aluminum head bolted to an iron block.

 

if you don't need pipe tape to seal the brass fitting. you could try some anti-seeze on the fitting to make sure it can be removed. but you shouldn't run into any problems with the two metals reacting with each other

 

Having poked around under the hood some more this week, I'm starting to think that if the block drain plug was accessible, MINI would instruct its service techs to open it when draining the cooling system.

It seems like it would be a lot easier to splice a fitting into the upper heater hose than to reach that drain plug. Coolant flow from the cylinder head to the heater core is unregulated, according to the Bentley manual.

 

A lot of people put the temp sensor in the bleed valve in the radiator hose in front of the block. May not be the best location, but it is certainly the easiest to access.

Good luck!
Ken

 

Thanks, Ken.

The radiator hose is very easy to access, but you're right; the water temp readings at that location are valid only as long as the thermostat is working properly. It's a compromise I'd rather not make on a daily driver.

Auto Meter makes a selection of cooling hose adapters, one of which should splice nicely into the upper heater hose. The sender could also thread right into the heater hose bleed screw fitting.

 

It's not 14x1.5. That is the engine oil drain plug size. The water block plug is under the exhaust manifold and is 12x1.5. I have engine out now while rebuilding the transmission, and just put a tap into it to verify. For those that search via Google for the answer.