My 88 pickup with the Z24i engine appears to be losing coolant, but what's weird is it only seems to happen when I'm driving. I noticed the leak because I kept finding the coolant overflow tank empty when I just refilled it maybe a week earlier, the radiator is sometimes low on fluid, and I can see droplets of coolant on the bottom of the front frame ready to drop off when I'm under the truck doing other service work. I'm thinking maybe it's the water pump but I can't say for sure...I saw the mention of the hole in the water pump that indicates failure in my Haynes manual, but it was not clear whether or not the hole was on the top or the bottom. I think I can see a hole on the top, but I'm not 100% sure as it's pretty dirty in there, and either way I didn't see real evidence of coolant coming out of that hole because of all the other dirt and oil there. Is this a reasonable assumption? I'm pretty positive all the hoses are OK as they're new, but I'm really not sure how the coolant is getting down to the frame like that in the first place. I took the skid plate off to see if I could see more "traces" of coolant but so far nothing that I can discern. I don't see any runs on the hoses either, so I'm a bit confused. And the overflow tank is solid as well.
On the water pump it's the bottom weep hole that you need to examine. First clean the area at the bottom weep hole. Start the engine and let it fully warm up which will build up the coolant pressure; now while the engine is idling, observe the area at the weep hole for any coolant leak.
Since you mentioned droplets of coolant on the front frame, the radiator may have a leak. After the engine has fully warmed up, shut it off and feel all around the radiator, top and bottom, for any trace of coolant; look at the radiator fins for wetness.
Don't say head gasket, I refuse to believe that! (actually I had considered it but there isn't much of any smoke from the tailpipe and no funny smells so I doubt that, though I do lose some oil as well...)
I'll check around the radiator next time it's warm, maybe get some UV dye too.
In addition to what rogoman said, and just for future reference... I once had a customer's self diagnosed "blown head gasket" turn out to be a worn out radiator cap. Ironically, a worn out radiator cap that won't hold pressure or let the system draw coolant back into the radiator from the reservoir as the engine cools really can turn into a blown head gasket.
1994 D21 2.4, 2wd, 5spd XE
Last edited by TheRepairMan; Feb 18th, 2013 at 08:53 PM.
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