Vehcile: 95 Accord, Ex, VTEC, AT

I recently drained and back flushed the cooling system on a 95 VTEC Accord, [approx 1.25 gallons]. I did not get a complete full system capacity drain [7+ US qts.] so, i posted about that and someone mentioned taking out the block drain plug. When i was back flushing eventually i got clear water, but then discovered that when i switched to hot water and increased the water pressure, suddenly the water gushed out dark brown. so now i want to take the drain plug out and do one last back flush. but there is one potential problem that is stopping me. someone told me that the drain bolt is a steel bolt going into an aluminum threaded block, and especially if the cooling system was never maintained, it will also have normal corrosion on top of the corrosion caused by the two dissimilar metals.

this accord was never maintained by the previous owner, so i know that drain bolt might be an issue. a Honda parts guy told me their techs never take those plugs out, and that he wouldnt do it if it was his car, that i could be opening up a can of worms, and if the steel bolt ripped the aluminum threads out, the motor would be trash. of course, it would be a difficult repair to do lying on my back having to drill, tap, and rethread, etc., but a machinist told me that it could be repaired, and asked why Honda put the procedure in the service manual if it was going to be so problematic.

well, i suppose that is the question. i'm curious to know if you guys are having any problems like i described or if you even take that bolt out? helms says the bolt is either a 12mm or 28mm bolt, has an aluminum washer gasket, requires liquid gasket to be put on the bolt, and gets torqued to 61 ft lbs. That is a significant torque, close to a lug nut torque, but i think this is more about possible severe corrosion, from being poorly maintained along with the issue of the two dissimilar metals. in the meantime i was advised to put coolant back in and see if it stays clean or gets dirty.

your thoughts?

 

while doing my motor swap, i had to drain my coolant. i unscrewed the plastic plug on the radiator and the steel bolt located on the rear of the engine. dont remember how much fluid came out of the steel bolt, but i remembered there was a bit. taking out the steel bolt to flush cooling system wont hurt the motor, just dont over torque. refer to a automotive repair manual.

 

Unless the drain plug in the f22 block is in a completely different spot than it is in the f23, it's not the lowest point in the system, the bottom of the radiator is.

just a thought.

 

Easiest way to flush with out a machine is loosen the pet **** and pull off the lower radiator hose and upper. Take a reg. garden hose and spray it into the upper hose. It will flush the block good enough for anybody.

 

I've never had a problem with block drain bolts.

 

[QUOTE=jweller;36950685] Unless the drain plug in the f22 block is in a completely different spot than it is in the f23, it's not the lowest point in the system, the bottom of the radiator is.

that's technically correct, but I was comparing the heater valve area with the drain plug. so, then I need to edit my post to reflect that fact better. so, the problem with using the logic of the lowest point in the system as the best drain point, is that although it is technicaly correct, it misses one important fact. there are areas in the block that are at a lower level that hold the coolant, and will remain in there unless the drain plug is pulled to release the fliud from those areas. in other words, there are pockets that hold the coolant by gravity in that area of the engine, so the rad petcock, although at the lowest point, cannot drain all the coolant/water, that would defy gravity.