Thread: overheated motor- think I blew out water pump rear seal

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somehow I lost a ton of coolant and didn't know it and I ran my truck and the temp gauge never got high, which I later found out was because there was no water in the top half of the block, it was so low it couldn't pump up that high.
I smelled something and got home and it was steaming and spraying out the bottom somewhere, impossible to tell because of all the steam.
I've replaced some hoses that I thought were the culprits, but now it appears that plate on the rear of the water pump is dripping. I can barely see but the area it drips from now has got to be that.
Does that sound like a good possibility?
After I shut off the motor steam was jetting out of one spot somewhere around that area for a good 10 minutes, I couldn't tell exactly from where because if I tried to feel the location it would burn too much to keep my hand there.

I wonder now if I damaged the heads since they were basically totally empty of water. I tested my thermo and it works fine, I think it was so low the temp sensor and thermo didn't get hot because no water touched them.

Sure it's possible. It sounds like the gasket on the rear cover, which gives access to the impeller & bearing, failed. It's also correct that if the water level is too low for the pump to get suction you won't see any initial heat indication on your water temp gauge. You didn't say what engine it is, but assuming a SBC here's a picture of the complete gasket set for the water pump (just to show what you've got).

SBC water pump.jpg

About all you can do at this point is change the water pump, fill it with coolant and start it up to see if you messed things up by severely overheating the engine. Watch for white smoke from the exhaust, check the oil to ensure that it's not leaking coolant into the crankcase (head gaskets), and pray. Probably a good idea to do a compression check and cylinder leakdown test if it acts OK on the initial run. Just my $0.02, and you may get other ideas to consider.

thanks for the reply
it is a BBC actually
yeah hopefully I didn't bake those heads and the water pump is the final leak

Same basic gasket shapes (not sizes) for the BBC. Also, most people don't bother but I'd check the torque on the replacement pump rear cover bolts before installing it. I had one that was loose on a new, out-of-the box pump, and it didn't take long to blow the gasket.

fill it back up with coolant and use a cooling system pressure testor to pump up the system with around 20 lbs pressure----with the leak as you described it water will be running out of any external leaks
AutoZone loans tools------

Pressure Tester Adapters at AutoZone.com - Best Pressure Tester Adapters Products for Cars, Trucks & SUVS



if dipstick has water droplets on it you have some internal problems

check dipstick and breather caps for moisture , milky looking stuff

And even tho you posted in the BBC Engine talk forum, most of us just go to todays posts and miss the title of the forum so we usually have to ask what type engine

Good advice from Roger.
What usually happens is that the bearing goes south, allowing the impeller shaft to wobble and wipe out the seal and you'll begin seein' puddles of water on the ground. Most often, the bearing is wiped out because its effective service life is over, but sometimes the bearing is wiped out due to excessive tension on the pump drive belt, so pay attention to that when you get her back runnin'.

I'd at least do a compression test on her. Here's the procedure....
Get yourself a good screw-in compression tester, as opposed to one with a rubber tip that you hold into the spark plug hole.
Warm the motor to operating temperature.
Remove the air cleaner.
Use wire or string to tie the primary throttle blades wide open so the motor can breathe.
Disable the coil by removing the hot wire from it to prevent a fire.
Remove all spark plugs to make it easy for the starter motor to turn the crank.
Turn each cylinder through at least 5 compression cycles (chuffs) to insure max gauge reading.
Write down the cylinder number and the reading for each cylinder.

A good running low-compression ratio motor with stock or slightly hotter cam and good ring and valve seal will generally show ~140-150 psi on each cylinder. 165 psi is the generally accepted limit for using pump gas, however with a good, tight squish of 0.035" to 0.045" and a state of the art heart-shaped combustion chamber with no sharp edges anywhere, I have seen motors operated on pump gas with compression tested in excess of 200 psi.

One other thought, if any water or anti-freeze solution has gotten into any of the cylinders, the spark plug for those cylinders will look like brand new because they will have been steam-cleaned.

.

well I don't have a compression tester, but I do have a leak down tester, I got it years ago when I was first putting the motor together and wanted to make sure it wasn't junk.
I will try that.
I only have about 6k miles on the pump, but it's a good 10 years old so maybe time has gotten to the bearings. I also only have two accessories (alternator/power st) other than the water pump of course, and they are both on the same side so all that tension is in the same direction. I'm sure that's hard on the bearing too.
thanks for the advice, I really hope I don't find a major issue once I get the pump fixed up from that overheat.

The pressure tester would be more ideal.
they can be rented at some of the big box part stores...
filled the system, pressurize and check the shaft seal and the rear pan and gaskets. As well as the hose connections / hoses and radiator.