desertmike1

Kind a looks like a casting line. But even if it were a crack, Doesn’t this area only see crank case pressure?

There would need to be a crack/gasket leak between the Chamber, and the cooling system. In order to Pressurize the cooling system. Are you going to have the heads inspected by a machine shop.

When did the problem first show up...right after the heads were installed?

Did you install the heads and water pump at the same time?

Black89Z51

Did you pressure check the cooling system before you took it apart?

jhammons01

A pressure test may not show a leak...the leak may be going one way and not the other.....

Super compressed gasses seeping through a leak is not the same as pressurizing a coolant system to 15psi cold.....

Black89Z51

The problem I see with the "super compressed gasses" is that there were no hydrocarbons in the coolant when he checked. I don't feel the head gasket was blown in my own opinion.

I would have run it with the cap off. If coolant shot out of the tank, then yea, I would call it a head gasket. But the lack of HC and a super pressurized coolant system, again in my own opinion, tell me it's something else.

jmgtp

Responding to the above....
A friend recommended a machine local machine shop and I’ll be stopping by tonight with the heads to see if they can pressure test them and if they check out good to make them flat again. It may/may not have been a HG. I don't know - what I decided is that since it did overheat I didn't want to risk that I fatigued the HG or warped the heads only to have another problem down the road so off with the heads! I am also addressing the rest of the cooling system- rad cap, thermostat, hoses, remove radiator to clean. I think wiring a light to the WP is a great idea. I'm going to talk with my dad (electrical engineer) to see just how I can do it. I'd like to use an LED somewhere inside the car that remains ON as long as the water pump is running - that way I have a permanent indicator. What would be even better is 2 LEDs, a green one that illuminates when the waterpump is running and a red if it stops.


I’m starting to round up my parts list for reassembly and I’m trying to decide on what head gasket and head bolts to go with. I previously went with the Felpro Impala gasket and Felpro head bolts. Obviously, I had a failure somewhere. I’m in no way suggesting that it was the HG or bolts but I want to make sure I pick the most suitable parts for my motor.

Does the standard Corvette gasket seal better than the thinner Impala gasket? If it does I’d rather give up the few ponies afforded by the Impala gasket to ensure a little more reliability. So my question here is, does any particular gasket offer better reliability/resistance to failure? I believe MLS gaskets are out of the question since the block is not getting machined.

96GS#007

I used the Impala gasket (albeit the OEM version) for years, it seals fine. I always use ARP head bolts, just a personal preference.

I'll see if I can find my old wiring schematic that I used for the water pump warning and operating LEDs.

Black89Z51

I'd go with the ARP head bolts for sure. Depending on how much material has to be removed from the head, you might want to consider some Cometic MLS gaskets. I'm not sure if you're blocks been decked or not, so compressed thickness will play a part.

leesvet

I'm not a 'fan' (no pun) of the water pump wired into the fuel pump circuit...thats unreliable. I recall reading somewhere that the fuel pump can shut down briefly under certain conditions/situations, stopping the water pump also. It may be only for a second, but it stops.
There is absolutely no reason why this pump can;t be wired into one of many "always on" circuits off the jumper post or one of the fusable link circuits. Piggy backed circuits cause multiple failures...domino effect.

Black89Z51

Or at least wire in a relay to the "always on" circuit and draw power from the battery or fusible link block to the pump.

jhammons01

I don't want to reread for accuracy, but think the OP checked the coolant after refilling with fresh coolant......I could be wrong.

When a car is overheating and no one can figure out why.....it's usually compression gases getting into the coolant channels

if the HG is blown and the coolant is seeping into the cylinders, you'll know by the telltale white smoke pouring out the exhaust on start-up or slightly as the (not likely) car runs....

This car spikes in temps and has coolant missing.....

jmgtp

I wired the waterpump to the PCM output for the fuel pump relay (not the fuel pump power wires). I did this because as long as the motor is running the fuel pump is running and using the same 'signal' wire for both relays made sense since one should never run without the other. I've never heard of any situation where the fuel pump stops for a running engine, I believe that is false unless you can show me where you saw this documented? I believe the only cases that a fuel pump stops for a running engine are if oil pressure drops too low the fuel pump will kick off to save the motor, but this also means the motor stops and if the air bags go off the fuel pump is disabled (I think), but if the air bags are going off the water pump is the least of my worries!

I did do the hydrocarbon test after replacing the lost coolant. I had trouble doing it accurately because the waterpump pumps coolant in right beneath the radiator cap, so if I seal the block tester against the expansion tank and try to draw air in it inadvertantly draws coolant in and ruins the test.

There was a significant amount of coolant missing, and a lot of 'air' in the water, but it was not burning any coolant through the motor. The exhaust was clean, the spark plugs look normal and the engine didn't miss a beat. The coolant was being forced out the expansion tank, filled the overflow and then onto the ground.

I'm considering going with a 3 core all aluminum radiator during this overhaul as well. I can't afford the good stuff (like a Dewitts), I'm considering a Champion 3 core aluminum which can be afforded for around $220.

jmgtp

Also, having trouble finding an aftermarket head gasket that is the Impala compressed thickness? I believe the ones I just pulled off my motor are 1074s and I now see that those are .039 compressed height. I believe the Impala gasket is .029 compressed height... yet I can't see to locate an aftermarket LTX HG that meets that spec.

96GS#007

Victor Reinz or any GM dealership.

jmgtp

Thanks I found: VICTOR REINZ Part # 5898
.026 compressed height

ajsc4

When was the last time you cleaned the air cleaner? This is a long shot but have seen it happen. Highway driving, engine can't breath and overheats. In town driving, engine dosen't need as much air.
Just a thought.

leesvet

I've got other reasons why I don;t care for that set up. I cannot tell you where I saw that FP info but I did read that somewhere in the FSM or some other GM article..since those are the ONLY ones that I really pay attention to. Newer ECMs do that for the rev limiter for sure...

One more GOOD reason to rewire...
you piggyback a ECM controlled ground circuit possibly increasing the load on the circuit with a high amp motor. Not good. But, if it makes sense to you and its your car, have fun ! I would be more inclined to source power that was not a controlled ground circuit.Especially with a motor. A "clean" source so there was no doubt as to the reliability or the possibility of doing harm to another system.
Good luck with the hunt.

desertmike1

I agree; even if your only using the ground signal to complete a ground circuit for a control coil in a relay, you'r still increasing the overall load on the ECM/PCM output...
to protect this circuit you could use a small portion of current from the fuel pump relay [B+ output] to energize a "seperate" Relay for the water pump.

Power for the second [Water pump] Relay could be routed directly from the battery with a fuse. You could then Tap into the water pump relay (output) to alluminate a small indicator lamp in the cabin.

Just out of Curiosity (for anyone) what are the benifits of an electric pump anyway?

93 ragtop

FWIW I used a pink wire that went to the fan relays for my signal. Its always hot when the switch is on. And it was located on the fan shroud, close to the pump.

jmgtp

ok ok, I will consider rewiring it. And just to be clear, the WP has its own power/ground wires - I wouldn't dare piggy back those off another accessory. I am only using the fuel pump pinout from the ecm for the coil on the relay - a negligible power draw.

Heads are at the machine shop. I was told it will be about a week turnaround (they're busy by the looks of the place) to pressure test and if they pass they will need to be resurfaced as well.

edit: Also, meant to mention that the electrip pump has been on for about 2 years and has never given me a problem, I don't believe it was the cause of the issue. The reason I went with an electric water pump when the original pump failed is because a few aspects appealed to me: better flow at low rpm, less parasitic drag, no chance of watering the opti (eliminates weep hole all together).

93 ragtop

[QUOTE=jmgtp;1580638746]ok ok, I will consider rewiring it. And just to be clear, the WP has its own power/ground wires - I wouldn't dare piggy back those off another accessory. I am only using the fuel pump pinout from the ecm for the coil on the relay - a negligible power draw.


QUOTE]




Hey, I agree with you. I dont believe that is your problem. If it lost signal to the waterpump, then the fuel pump would drop out as well, which would shut the car off.
I just threw out how I wired mine, not to say your way was wrong.
FWIW, if I was to bet, id say it is in the gaskets, etc. Hopefully you will have it fixed when put back together.