offroadjim

offroadjim

Afterthought: The thermostat on the car was replaced approx. the same time that the green antifreeze was put in. Would the system need to have been bleed after that (it wasn't) and could that be causing the noise?

2LZ

Bust out a long screw driver (or mechanics stethoscope) and confirm where the nose is coming from. It could even be an idler pulley or something else close by the w/p.

I run Dexcool (the red/orange stuff) in all my GM's. Regarding flushing, when I have the w/p off, i ram a garden hose in all the w/p ports to flush the block. Makes for a clean garage floor when you're done too..

offroadjim

Garden hose in the water pump openings correct?

2LZ

In the block. Yes, the water pump openings. I stuck the hose in and cranked it up.Mine wasn't mucky but anytime I can flush it out, I do.

c4cruiser

The correct coolant for your '92 is the green ethylene glycol antifreeze in a 50% solution with distilled water. The orange Dexcool and the green coolant do not mix together. A dark brown sludge-like material will form and it's very difficult to get it out of the cooling system.

The FSM for the '92 states that the knock sensors should be removed for flushing the block. There's a good chance that there is sludge that has formed and you may need a thin rod to scrape out the gunk so it will drain. Replace the sensors, refil the system with water and start the engine. After it reaches operating temp, shut it off and let it cool down to about 100 degrees and remove the knock sensors and repeat for 3 times.

Once there is just clear water coming out, you can fill the system with a 50-50 mix of the green coolant and distilled water. It could be dangerous to remove the water pump and use a hose to push water through the block. The OptiSpark distributor will fail if it gets wet! You can protect the Opti by covering it with something like aluminum foil while the water pump is replaced.

offroadjim

JimLentz

Pull the belt and start it and if the noise stops it isn't the water pump.

offroadjim

JimLentz

Correct because the optispark and water pump will run without the belt.

VeryUnoriginal

Pull the belt off and see if the noise persists. Also, like others have said, get a mechanic's stethoscope and see if you can pinpoint where the noise is coming from. Check all the accessories and pulleys and see which one is loudest. As for the coolant, if someone put Dexcool and green anti-freeze in together it will start to sludge up and get a lot of nasty stuff in the cooling system. I'd recommend going to an auto parts store and get one of the coolant flush kits and pour it in the radiator. Let the car run for a bit with the heat on so it gets into the heater core and then drain the coolant. Next, fill it up with just water and let it run up to operating temperature again. Drain the cooling system again and note the color of the fluid being drained. Repeat that until it's just water coming out and then fill your car up with the correct antifreeze. I had to do it to my '93 when I first got it and I haven't had any more issues with the cooling system in almost 8 years. Good luck man!

offroadjim

rjacobs

You can run green or you can run orange(dex-cool)... It doesnt matter.

BUT

You cant run them together, they dont mix.

You need to drain the radiator and block(pull knock sensors), do a flush(4 gallons of distilled), drain it all again, possibly do that a second time since you said you have green and orange mixed...

Then refill with fresh Dex-Cool mix...OR green, whichever. I prefer Dex-Cool personally, but as long as you dont mix them, you can use either.

Paul Workman

Marc Haibeck is a ZR-1 guru - specializes in the LT5/ZR-1. He wrote an article detailing proof of gasket failure (at least in the LT5) as result of using Dex-Cool in (at least the earlier) LT5 motors i.e., may not affect the 95 ZR-1s or maybe even the 94s(?). Apparently the gasket material changed in the mid 90s allowing use of the organic corrosion inhibitors found in Dex-Cool. But, his recommendation is to stick with the "GREEN" silicate base inhibitor to be safe. Replacing a head gasket on a SBC is a half day job for a skilled DIY'er. But, it is a major job on a DOHC motor (that has to be removed in order the cams be reinstalled and phased).

But, like Marc says, the GREEN stuff is going to be around because it is used in many other applications like diesel motors. So, why risk experimenting?

Granted, the LT5 is a different animal from the L98/LTx motors, and IDK if the compatibility issue in the LT5 extends to include the SBCs. Best not to experiment and use the type coolant recommended by GM part number for the vintage motor(s) in question. But, certainly C4s in the late 80s and early 90s preceding Dex-Cool may be at risk - not to mention the issues resulting from mixing the two types!
Possibly the late C4s gaskets were OK with the Dex - IDK. But, the point is, it would behoove one to use the "GREEN" stuff until he knows for sure that Dex-Cool is compatible with your head gaskets. Just sayin.
.

offroadjim

Smokeysvette

Your '92 should have the green antifreeze. That's what GM filled it with when it was built. Why anyone would go to the orange Dex-cool is beyond me. So if the car has green like it should use it! If it has orange, personally I would completely flush it out as others have mentioned and go with the green with what the car had in it originally. Just my .02's worth.

offroadjim

offroadjim

offroadjim

Paul Workman

I think I did use a single wrap of teflon tape on my new knock sensor. SBCs traditionally hold around 18 quarts of coolant.±.

A coolant hydrometer is a cheap enough gadget at any auto parts store and is simple to use. Check to see the concentration of GREEN coolant is sufficient to protect well below the temperature you would expect to get down to - 50/50 should take you down to around -30ºF or -34.4ºC. But, because some water remains after flushing the block, it may be a good idea to have some undiluted coolant handy to increase the protection.