94 Explorer Freeze Plugs
 

Just acquired 94 Explorer, V6 4.0L I think, that has built up too much pressure in the cooling system and blew out the freeze plugs, also has small engine knock. I am a tax accountant, and client who owns repair shop had vehicle come in for repair, he replace freeze plugs and they blew out again, said customer could not afford repairs, so I bought from customer. Mechanic says best thing to do is get another engine from a junk yard. Mechanic is a foriegn car specilist and does not like messing with US cars. I am just wondering if current engine is not salvagable, cheaper than replacing with junk yard engine that you still are not sure what you are getting. Have had people tell me may be clogged radiator, or blown head gasket? I do not have a clue! Oil is low, but does not appear to have any water in the oil. Any diagnostic help would be appreciated.

Thanks / Mark

Yeah I usually bring my Explorer to the Honda dealer for repairs, sometime BMW if I'm feeling rich - NOT!

We first need to know what's going on. It makes no sense that pressure will blow out a freeze plug that is properly installed. You'd blow a hose wide open before the freeze plug. You have a radiator cap that is set to blow off at 15 or 17 PSI. This is the first point of pressure release. Put a new one on for the hell of it but that's not your problem.

If you have a blown headgasket, the car would run bad and you'd have other symptoms like bubbles in the radiator - a lot, coolant in the oil, steam out the exhaust pipe, a loss of coolant... Got any of this?

I don't have the freeze plug spec in front of me but my guess is that it is a metric size since these motors are built in Cologne, Germany. Maybe it was replaced with a SAE size? Did the first one blow out or rust out because your too poor client couldn't affornd antifreeze and ran only water. Reason is I have yet to hear of a freeze plug just up and blow out on these motors.

You should find someone local to you who knows these motors a little better and get another opinion. He could run a test on your computer too which might be storing some codes to help with the diagnostics. Or go to Autozone or the like and get a computer read for free and post the results. We all out here have most of the codes memorized - especially OBD II's - right boys?

Freeze Plugs
 

Thanks for your replay and insight. Makes sense - Inside of radiator at neck has brown rust color - thought that originals rusted would be very possible. Mechanic said freeze plugs were difficult to get to, so quite possible attempt to re-install resulted in them not seating properly and falling out with minimal pressure.

Do you know how many and where the freeze plugs are located?

Also - will ask mechanic Monday if he has any fault codes - will let you know if I get any.

Thanks again / Mark

On my 92, a freeze plug gave way to rust and released all the coolant with my wife a few years ago. I can't remember the size (like I said a few years) but it was SAE, and it was an oddball size, and a tight fit. I ended up using one of those rubber compression type plugs, and it worked. Unfortunately when it ran hot with her, it had spun the bearings, and I ended up putting another motor in it. x( But the new motor still runs great at least. Anyway, Like Jharger said, if it's building up that much pressure (to blow a good freeze plug) other stuff will blow first (hoses, radiators, etc.). You may want to try the rubber compression style plug, but you must be VERY careful with these. Make sure to clean the hole thouroughly and don't overtighten. Overtightening one of these can bust your block.

Mark - 4 or 6 plugs - too hot out in the garage to look right now (Phoenix). you can try a rubber plug - should work. but these are symptoms to the real problem. Rust in water is the first thought.