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News: Water pump and optispark.


Aug 22, 2007
Windsor, CO
1996 Black LT4
Hi folks. I've never posted here before but have some information ya'll might find helpful. I always look around here to learn how to deal with issues concerning my '96 LT4 and it has helped tremendously. Thanks for your help and maybe I can contribute as well.

Started having a very slow coolant leak that would show up as a small puddle under the car. Also, the serpentine belt would slip at slow speeds making turning the steering wheel tough. I drained the coolant system and replaced all the hoses that looked questionable including the clamps as well. Cleaned up all the coolant on the belt and pulleys. Fixed right! Not so much. Continued to look for leaks, time and again, but found none. I continued to drive the car and figured I'd add a little coolant now and then. What else could I do? No harm no foul right? This went on for a couple of summers.

One day I drove over to the post office, about a mile or so, and when I got out of my car I noticed steam rolling out of the hood. A look underneath and my coolant was pouring onto the ground. Drove it straight home and left a coolant trail the entire way. This is when I learned about the "weep hole" in the water pump. What? What's a weep hole?

Thanks to the good bloggers at Corvette Action Center I got schooled on the weep hole. I replaced the water pump and all was good. Right? No more leaks. I'm ready to go.

As required by state law I took my Corvette down to the emissions test. She always passes. Not to worry. Failed the hydrocarbons emissions test (unspent fuel) big time. There was no check engine light or failure codes thrown. What could be the problem now?

Back to the Corvette Action Center where I learned about the vulnerability of the opti-spark and coolant leaks causing it to fail. Replaced the opti-spark (expensive distributor). Oh yeah, you have to remove the water pump to get to it. I also figured after 20 years she could use a new set of spark plug wires and a coil. I had replaced spark plugs not so many miles ago.

Had her retested and she passed easily. My Corvette has never run so well since I've owned it. It runs very cool now. Right around 195°F to 210°F when the outside temperature is maybe 75°F. She pulls really hard when you hit the pedal. Too fun!:happyanim:

Moral of the story: If your water pump fails or even leaks, replace the opto-spark too. It's expensive but well worth the trouble. Hope I've helped someone else with this problem.
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I don't have an Opti in mine (L98), but something I read previously was rig a hose from the weep-hole around the Opti so if it leaks it does not deposit coolant on the opti.
Weep hole hose

Yeah, I've seen a few folks drill and tap the weep hole to attach a hose which is an excellent idea (hello GM engineers). I thought about it but doing these kind of modifications usually go wrong for me. I'd probably get shavings in the pump and be replacing it again. The pump I replaced lasted 90K miles and more than 18 years. I'm hoping for at least that long for the new parts. Thanks for the reply.

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