Nickster 7

I have had my 1995 Z28 since 2012. Back in 2013 (or 14, don't remember) my stock water pump failed, so to get it fixed, I ran down to the local auto parts store and picked up a cheap new one (not a re-man it said) for like $70 something.

We replaced the coolant with some "all color" Prestone, and bled the system, but ever since then, the car has always seemed to run hotter than it did before. I know everyone says 235 is normal, and recently in traffic I have noticed that when it gets to that temp, my oil pressure drops to around 15 or so according to the stock gauge, which still is alright I assume. It never used to drop below 20psi when at hot idle, and that bugs me a bit...

So, here is what I would like to know:

1. Is the cheap water pump possibly a cause of my car running hotter than it used to, and is there a certain coolant that I should run in my 1995 Z28? As mentioned, I used some "all color" coolant from Prestone, which is a light green.

2. Is my lower oil pressure a sign of wear and tear on the internals, or just possibly because of oil breakdown when it runs so hot? I get the oil changed at the dealer (non-synthetic) every 3,000 miles, or at least twice a year if I don't drive that far. My motor is stock and has 60k on it, and I don't beat the car. I drive it like a sports car when I take it out twice a week or so, but I don't redline it all the time or constantly hammer on it. It only drops below 20psi if I have been driving for a while and the temp is around 220 or so.

Fatdog2

Did you have the thermostat replaced?I here it's a good idea to replace the stat when ever the radiator is flushed.Also, the LT1 uses a very special stat.Also the gauges are not accurate especially the gas gauge.I think your car calls for the orange coolant.Mine uses the green and I'm happy with it.Do your fans turn on when they are suppose to?Hope this helps.

Injuneer

As oil heats up, the viscosity drops... it gets thinner. A drop in the idling oil pressure would be expected if the oil is overheating, along with the engine, and oil temp does track coolant temp. Fix the overheating problem

I would not agree that 235* at idle, sitting in traffic is normal. To me it means the cooling system is not 100%.

The type of coolant is not an issue. No matter what the color, extended life, normal life, green, orange.... it is all mostly (90+%) ethylene glycol. Just as a check, are you running a mix of no more than 50% coolant, with the balance water? Water has better heat transfer capacity than ethylene glycol, so you want to push water a bit above 50% if you are not expecting freezing temps. Don't get real high on water, or you will get in trouble with the boiling point of the mix.

A water pump with a poorly cast impeller, or excessive clearance would pump less coolant. Was there any sign of damage to the splines on the pump drive shaft? Could that possibly be slipping?

Did you CORRECTLY bleed the air from the cooling system?

Dex-Cool (orange) was not introduced until the 1996 model year, but it's not an issue. I've been running Dex-Cool in my 94 for almost 20 years with no problems.

Nickster 7

I did not replace the thermostat. I took the car to my neighbor down the street and he diagnosed that the water pump failed and leaked all over the opti, causing my misfires and stuff, so since the Camaro was my only car, I ran down to advance auto and picked up the cheap pump. My fans do cool the car when they are supposed to. It never goes into the red, but it gets close sometimes. As Fred states below, mine is a 95, not a 96, so it doesn't use the Dex-cool.

This was a while ago before I knew a lot about my car, but the neighbor knew about the reverse flow cooling system, because he was a service manager/tech for a while. Pretty sure we got all of the air out. He is always fixing other people's cars at his place. Anyway, we used some of the coolant, and almost the whole gallon of distilled water if I remember correctly.

The water pump I got was of course aftermarket, and it has always had an audible high-pitched whine, almost like a supercharger. Not sure why, but maybe that is bad clearances or cheap parts. It looked fine when we put it on the car. No messed up splines or anything. Maybe it would be best to buy an actual GM pump, flush the system, get a new t-stat, and re-do it?

As for the oil pressure, when the car is running at normal 180 (185?) temp, the pressure stays at 20 at idle.

Injuneer

Your oil pressure is fine. It's the high coolant temp that's the problem.

So the ONLY thing that was done was to change the water pump - nothing else was changed? And the engine ran cooler, particularly at idle, with the old water pump?

Bleeding procedure:

4th Gen LT1 F-body Tech Articles

moparman

I hate to be the bearer of bad news, but the opti you should buy is the Delphi. I don't think the AC-Delco is still available.

Injuneer

Pretty sure he is talking about buying a GM water pump, not an Opti.

Nickster 7

Yes, that is correct. Just the pump was changed. Same T-stat, same sensors, same everything. If I recall, it never ran that hot before.

Yeah, my opti is fine. I think it will be good for a while, because it is the vented opti, and I don't believe the coolant leaking all over it did any harm. How is the MSD opti? My buddy runs one of those.

Injuneer

MSD is no better than stock, maybe even not as good. Has its own set of problems.

moparman

Did I misread that post or what? I read it as saying the water pump took a dump on the opti, and he went to the parts store and bought the cheap store brand opti. I think I'll go stand in the corner for awhile.

The MSD is a crap shoot. You might get a good one, or you might get a bad one. My own experience was I bought a MSD cap and rotor, put it on, and the engine would not attempt to start. Replaced it with an OEM cap and rotor, and it started right up.

Nickster 7

Yeah, I figure it's usually hard to make something better than the factory did. I mean, when GM wants to make a performance car, they know what they're doing, they just have to tone it down a bit

Don't worry about it! But really, my main concern is the water pump. Maybe a good idea to get genuine GM?