cooling system help please

[lumberman]

I have purchased a 1987 half tonne with a 350 in it, and cant seem to find out why i am losing so much coolant. It doesnt lose any when its not running, but when i start it up it seems to drip quickly off of the lower rad hose.I changed the lower rad hose and clamp but it still seems to be leaking out the same amount. I try to fill the system but the upper hose never seems to have any fluid in it. The truck never overheats but if i dont add fluid every couple of days, i lose heat to the cab. After taking a long drive, i get out and check that upper rad hose and its still empty and it feels like the little bit of fluid near the engine is boiling. As the engine cools down it drains the coolant from the overflow bottle. Any advise on what it could be??? As you can tell i am not a master mech and any help would be great!

[rfmaster]

Lumberman

First, I would not drive a truck until coolant leak is fixed. It is too easy to overheat and blow a head gasket.

Check your water pump and radiator. Make sure that water pump to block gaskets are in good shape and mounting bolts are properly torqued down. Water pump seals are good for about 80 to 100k. A leaky seal will drip like you have described in your post. A radiator leak would leak for awhile after engine shutdown.

If there is no water in the upper hose – check for malfunctioning thermostat (stuck closed). Another possibility is an air bubble inside engine block which can be purged out with coolant flush.

Good Luck

//RF

[lumberman]

I pulled the thermostat and tested it like everyone is saying to in the threads(in boiling water). it opened up after about a minute in completly boiling water. i reinstalled the thermostat and refilled everything and brought the engine up to temp with the rad cap off and the rad full of coolant. the temp gauge got up to 120 celcius and the coolant didnt start to circulate. it actually just overflowed then sunk overflowed then sunk. in other vehicles when the thurmostat opened you could tell becouse it would start flushing like a toilet. any idea why this one doesnt do that? by the way after it got above 120 i got scared and put the rad cap back on for about ten seconds. i then took it off to see if it was cycling and it basicly emptied the rad out the fill spout in about two seconds lol. i guess thats why it says not to open when hot!! any suggestion on why system is not cycling?

[blaserman]

Sounds like you pump is not working. Also the leak on the lower hose could be coming from the rad it's self in that area. Check the area where the hose hooks up to, I had a small leak there once and had to have it redone. Just a couple of ideas.

[rfmaster]

Lumberjack

Most SBC thermostats open at 180F/80C - since it took over a minute to open in boiling water 212F/100C I have some reservations about your thermostat - replace it - it is a $5 dollar item.

Blaserman is also correct - check water pump. If water pump is working, and with fully open thermostat you should see cycling water in the radiator.

In cab gauges are not very accurate, since 120C/248F coolant temperature can only take place in closed (under pressure) system. But, if thermostat stays closed, for while, it may case pressure spike (and high temperature) since you verified that thermostat opened a minute later after being in boiling water.

I hope it helps

//RF

[lumberman]

thank you everyone for the help! it did turn out to be the water pump leaking out. i changed the pump and the thermostat and all is well again. as much as i enjoyed that job i dont think i want to do it again, so one last quick question. could the failing thermostat be the reason for the water pump failing?
again thank you all for the help and hopfully one day i might be able to help someone else.

[rfmaster]

You welcome.

As far as water pumps go - well, stock water pumps are good for about 80 k. Sometimes less, sometimes more depending how lucky you are. Typically bearing seals go first followed by wobbly – whining bearing. On one occasion I have seen a water pump impeller brake of the shaft. The car, 1960 Biscayne, set in storage for 14 years – cooling system was not properly preserved resulting in a rotted radiator, water pump, block plugs and rotten intake manifold bolts. Block had to be junked – it was just rotten through and through.
A stuck thermostat will put additional load onto water pump – over time pump may go out.

[blaserman]

Glade you found the problem. Any time you need help just post it and someone will reply. Just like building a ball field "build it and someone will come"

Art