coolant leak - ZR-1 Net Registry Forums

ZR1CK · 02-12-2018

Greetings fellow Z's,
While attending Corvettes at Carlisle last year my Z sprung a pinhole leak in the lower rad hose

!!!! NOT AN EASY FIX, especially away from home. Anyway, I rented a Uhaul trailer & truck (R.I.P. OFF) and hauled it back home to Liverpool, NY. A buddy of mine suggested replacing the coolant with Evans waterless. I hemmed about it a bit and decided to give it a go. I followed their procedures, but after blowing out any trapped water pockets and refilling it with their prep fluid, I noticed a leak coming from between the rear block and bellhousing!!!!!!!!!!!! Are there any expansion plugs at the rear of the block that might have partially blown out or loose? Or any other ideas?
HHEEEEEEEELLLPPPP

Ccmano · 02-12-2018

While possible, a freeze plug leaking, is highly unlikely. More likely is a leak from an injector housing gasket into the valley of the motor. The valley has a drain tube that comes out behind the flywheel. Get a pressure tester (borrow from local parts store) and a borescope (very cheap on eBay, attaches to your phone) You inspect inside the valley that way without disassembly.
H

ZR1CK · 02-13-2018

I really appreciate your input. I was afraid I was gonna have to get to the rear of the block. What you describe is much easier. I couldn't think of anything else it may have been. I've had the plenum off a few times already and didn't recall seeing any hosing or coolant passageways. I had to replace the coils for miss-firing. I replaced them with Accels but ended up with the same problem less than 2k miles later. I then replaced them with B&D coils and they've been working great since then, around 7 years ago. The year after I replaced the coils I noticed the engine was skipping. Turns out this time that 2 fuel injectors were to blame AND I also noticed a slight smell of gas. After pulling off the plenum again, I noticed that the fuel rails were also leaking, and right next to and over the starter! For this I blame the ethanol in the fuel. That's all that was available at that time, now I use only ethanol free gas. Anyway, what I'm getting at is that if what you say is in fact thee problem, it'll be a much easier and quicker fix. I'm hoping that's all it is. I do have a goose-neck camera to look inside and under the plenum but not very good as tight as things are under there. I've scoped it before looking for critters, as I've had that issue before too. I'll be digging into it when the temps come up a bit as I reside in Central NY and do not have a heated garage. Thanks again and I'll be posting my results in the, hopefully, near future.

jss06c6 · 02-14-2018

Definitely agree with Hans. I believe you may have a leak under the plenum. No freeze plugs on the back of the block. You do have freeze plugs on the back of the heads however. Doubt this is where the moisture is coming from. Note the drain line, which is plumbed to the valley to allow moisture or other fluids drain. If obstructed (pretty common), the moisture has nowhere to go other than out the back of the valley between the heads. Coils and other electronics don't like moisture! Get a borescope and give it a good look..

ZR1CK · 02-16-2018

Hey, thanks for the pic. I do recall seeing a hole in the back area of the valley under the plenum when I did the other repairs. Didn't notice the liquid coming out of the tube though. I'll still be pulling the plenum anyway to get at whatever the issue is.
P.S. nice headers.

02-12-2018	#1
ZR1CK Join Date: Jan 2013 Location: Liverpool, NY Posts: 35	coolant leak Greetings fellow Z's, While attending Corvettes at Carlisle last year my Z sprung a pinhole leak in the lower rad hose !!!! NOT AN EASY FIX, especially away from home. Anyway, I rented a Uhaul trailer & truck (R.I.P. OFF) and hauled it back home to Liverpool, NY. A buddy of mine suggested replacing the coolant with Evans waterless. I hemmed about it a bit and decided to give it a go. I followed their procedures, but after blowing out any trapped water pockets and refilling it with their prep fluid, I noticed a leak coming from between the rear block and bellhousing!!!!!!!!!!!! Are there any expansion plugs at the rear of the block that might have partially blown out or loose? Or any other ideas? HHEEEEEEEELLLPPPP

02-12-2018	#2
Ccmano Join Date: Jun 2006 Location: Sparks, NV Posts: 2,852	Re: coolant leak While possible, a freeze plug leaking, is highly unlikely. More likely is a leak from an injector housing gasket into the valley of the motor. The valley has a drain tube that comes out behind the flywheel. Get a pressure tester (borrow from local parts store) and a borescope (very cheap on eBay, attaches to your phone) You inspect inside the valley that way without disassembly. H __________________ 90'ZR-1 #1461 Red/Black Ported Intake, Degreed Cams, OBX Headers & Exhaust, Fidanza FW, Secondary Delete, Custom tune, C6 GS Wheels. Sold 08 C6 Z51 Crystal Red Metallic Sold Vararam Intake, Tune, Sold 05 C6 Z51 Red/Black Sold 90'ZR-1 #1723 Black/Gray Sold but not forgotten 91' Z51 L98 White Vert. My First, you always remember your first. Sold. Last edited by Ccmano; 02-13-2018 at 08:14 PM.

02-13-2018	#3
ZR1CK Join Date: Jan 2013 Location: Liverpool, NY Posts: 35	Re: coolant leak I really appreciate your input. I was afraid I was gonna have to get to the rear of the block. What you describe is much easier. I couldn't think of anything else it may have been. I've had the plenum off a few times already and didn't recall seeing any hosing or coolant passageways. I had to replace the coils for miss-firing. I replaced them with Accels but ended up with the same problem less than 2k miles later. I then replaced them with B&D coils and they've been working great since then, around 7 years ago. The year after I replaced the coils I noticed the engine was skipping. Turns out this time that 2 fuel injectors were to blame AND I also noticed a slight smell of gas. After pulling off the plenum again, I noticed that the fuel rails were also leaking, and right next to and over the starter! For this I blame the ethanol in the fuel. That's all that was available at that time, now I use only ethanol free gas. Anyway, what I'm getting at is that if what you say is in fact thee problem, it'll be a much easier and quicker fix. I'm hoping that's all it is. I do have a goose-neck camera to look inside and under the plenum but not very good as tight as things are under there. I've scoped it before looking for critters, as I've had that issue before too. I'll be digging into it when the temps come up a bit as I reside in Central NY and do not have a heated garage. Thanks again and I'll be posting my results in the, hopefully, near future.

02-16-2018	#5
ZR1CK Join Date: Jan 2013 Location: Liverpool, NY Posts: 35	Re: coolant leak Hey, thanks for the pic. I do recall seeing a hole in the back area of the valley under the plenum when I did the other repairs. Didn't notice the liquid coming out of the tube though. I'll still be pulling the plenum anyway to get at whatever the issue is. P.S. nice headers.