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Discussion Starter #1
Moving the petcock tab from horizontal, stops at vertical position and nothing comes out, have tried the following:
WD 40 though the spout and around the tab and move tab many times and also tried pulling out while doing so
Reservoir cap off.
Breather screw loosened and fluid weeping out.
Would really like this petcock to work without breaking it (Delco tab/insett costs $22 plus shipping), as a last resort will disconnect lower radiator hose.
Thank you.
 

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I asked the local Oil Express store how much would they do an AF exchange for and they said 75 dollars. They said it was OK to use standard anti freeze as long as the Dexcool was completely out. Everything I read explained why you needed to stay with Dexcool and I told them I only wanted Dexcool. They said they don't have any, but if I brought my own they would do it for 45 dollars. So I went to the local Wally world picked up 2 gallons of concentrated Dexcool and 2 gallons of distilled water. They had an exchange machine that they purged out all the standard antifreeze that they had been using and mixed in all the Dexcool and Distilled Water that I provided. They exchanged the DC in my system through the overflow reservoir without opening the radiator drain. I thought it was pretty cool because it was cheap and I did not have to deal with disposing of the Dexcool and getting dirty. I pretty much was 5 feet away and watched the whole process which always makes you feel better. This method does not clean your cooling system nearly as good as going through a flush with water until everything goes clear yada yada yada, but it does a good job IMO.
 

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About the plastic "petcock" thing. Years ago, I took the then current car in to do a flush and fill at a local indy shop. Apparently, the petcock was troublesome and they cracked it using who knows what to loosen it to get it to flow.
About 9 months later, daughter was driving the car and she said. . "steam was coming out under the hood and I could see "water" spilling on the road behind the car when looking in the rear view mirror." The petcock was cracked off flush with surface where it screwed into the radiator. Had to get creative and extract the threaded plastic still left in there.
Did she pull over to the side of the road and stop immediately to call me? No. . . "I thought I could make it home". At which point the engine seized and then found out later the cylinder head was also warped and head gasket was leaking. $800 later for a repair at another local shop it was running again. But it was never the same. It used coolant a little at a time till the car was traded in. Got almost 10 years out of it but the last 2 were nothing but niggling repairs and band aids.

So. . . no matter what, you take you chances.
 

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Discussion Starter #5 (Edited)
I am on my third Delco #15781370 GM and they are not reusable and the only ones available on the market. (The Dorman brand will not work on Equinox even though it looks exactly the same. It also has a thinner diameter O ring) Once a new Delco is closed it cannot be turned open by hand, you must use the help of a tool to turn it counter clockwise.
When the new and fresh one is closed it does not leak, , it will drain alright but close it again and it will leak. Had to buy two new ones and threw away the original one because when I was finally able to take it out the O ring was cut thru plus almost cut thru at a second spot. The petcock it self looks perfect. I believe that if I could find a new O ring it may again seal.
I am not the sharpest guy though I have gone though 74 yearly cycles and what that entails. This is what I think:
1- My Haynes repair manual shows a picture of a petock which is a threaded plug, removable with a screwdriver. Too simple I guess or too hard to manufacture?
2-New design Delco petcock is very complicated structure; just imagine fabricating the plastic injection mold with all its intricacies, plus the molding on the radiator' "inside" into which it fits. I am no engineer but I will be discussing this one with my psychiatrist on my next visit as aging may be having a negative effect on my simple brain.
These indispensable little, disposable things cost from $25 to over $36 and nobody warns you of this magnificent experience. If you visit eBay you will see a veritable proliferation of merchants selling these. They know something I don't?

Forgive me for the lengthy release of frustration fellas but, I have a soft spot for DIY mechanics and I have the noble purpose of trying to save them from some suffering.
 

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I am on my third Delco #15781370 GM and they are not reusable and the only ones available on the market. (The Dorman brand will not work on Equinox even though it looks exactly the same. It also has a thinner diameter O ring) Once a new Delco is closed it cannot be turned open by hand, you must use the help of a tool to turn it counter clockwise.
When the new and fresh one is closed it does not leak, , it will drain alright but close it again and it will leak. Had to buy two new ones and threw away the original one because when I was finally able to take it out the O ring was cut thru plus almost cut thru at a second spot. The petcock it self looks perfect. I believe that if I could find a new O ring it may again seal.

Forgive me for the lengthy release of frustration fellas but, I have a soft spot for DIY mechanics and I have the noble purpose of trying to save them from some suffering.


Maybe apply a light smear of silicone grease to the o-ring on the new petcock? That way it might not bind and tear next time it needs to be opened? Some Ace Hardware stores have a great selection of o-rings.
 

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Discussion Starter #7
JayTee2014: I did, on the new petcock, take the O ring off and dabbed it well with Super Lube and put it back on gently, also put a light coat all of the piece. Do you favour silicone lube better?
Curiously the initial counterclockwise turning of the new petcopck required pliers just as in the old one that had been there for years. After that initial resistance I can turn it by hand but with for force. When I remove the new one, soon, will report if any damage is on the O ring. Meantime going straight to try and find a new O ring to fit.
thanks for your reply. Happy Memorial Day.
 

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JayTee2014: I did, on the new petcock, take the O ring off and dabbed it well with Super Lube and put it back on gently, also put a light coat all of the piece. Do you favour silicone lube better?
Curiously the initial counterclockwise turning of the new petcopck required pliers just as in the old one that had been there for years. After that initial resistance I can turn it by hand but with for force. When I remove the new one, soon, will report if any damage is on the O ring. Meantime going straight to try and find a new O ring to fit.
thanks for your reply. Happy Memorial Day.

Another place I have found for o-rings is the plumbing/faucet departments in home supply stores. I have matched up o-rings for other uses from faucet o-rings.
 

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Discussion Starter #10
wow, I wonder if its just easier to remove the lower radiator hose and let it drain.....
Yes that would be, after the fact, now the petcock is leaking and until I fix that.....
Absolutely that this vehicle should be drained ONLY through the lower radiator hose and nothing else!
I agree with you totally, hindsight is so much easier. Been here since 74 years ago and it's always smarter.
 

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What model year is this?

Every petcock I’ve ever removed has always been unmovable just using your fingers (plastic tabs never seem to give enough leverage to break it free). However, every one has also had a 6-point hex-shaped body that a wrench or adjustable has fit around very snugly, making it very easy to release. And I’ve never damaged an O-ring (although I remember replacing one *once* due to a drip that happened out of the blue one day, wishfully thinking that’s all it was, but then ending up replacing the radiator anyway - so the O-ring was probably OK).

Think I always release these things when they’re at least warm. Don’t know if that’s made a difference...
 

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Discussion Starter #12
Solutions

As previously suggested by someone else, in hindsight, drain radiator ONLY by disconnecting the hose that is between radiator and water pump. The drain hole is biggest.
Draining through the radiator petcock forces all debris, rust, etc. to this most restricted orifice, which is not smooth bored but has valleys and ridges formed to accommodate petcock. This then, very likely, is causing the problem of damaging the O ring when petcock is removed and not turning easily in or out. If the orifice is clean the petcock insert goes easily and moves as designed because I was able to clean and do it but, quickly gets crudded up again.

An O ring that fits the petcock, which is installed right now in my Equinox, and is not leaking after 3 days riding is:
Danco.com 96728, #11 o-ring (3/4" O.D. X 9/16" I.D. X 3/32") you get 10 rings in the little container. Purchased at the orange colored big home supply store. $2 and something. This tip will save you around $25.00 of buying a new petcock insert.

Lastly, to clear out the debris which would inevitably settle to the bottom of the radiator, I disconnected radiator hose and removed petcock insert, with garden hose nozzle sprayed full blast many times until water came out crystal clear.

Maybe they'll go back to using a simple screw in and out, plastic plug to drain radiators and avoid these wonderful complications.
After this extreme Prestone flush (of riding car with chemical in it for 3 days and about 7 times of flushing until water was clear) I can brag that my systems is very clean. I earned it!
 

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Just viewed this part online and it appears to be a piss-poor design. No hex flats on it to grab with a wrench or adjustable. Just the “vane” or tab to turn with your fingers, and that’s likely to snap off! Only saving grace is no threads on the barrel - just a molded shank on the very end that appears to only require a half turn to release.

I’ll probably *still* drain through this petcock, but only after heating up the coolant, which can be a little dicey if it comes gushing out suddenly. If the fluid behind the plug is hot, the petcock will *probably* release without any damage...
 

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Discussion Starter #14
Maybe apply a light smear of silicone grease to the o-ring on the new petcock? That way it might not bind and tear next time it needs to be opened? Some Ace Hardware stores have a great selection of o-rings.
Yes I do that everytime. thanks
 

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Sorry to resurrect an old thread, but I just did two coolant drain and fills on a 2015 Terrain V6. Now that I have done drains through the petcock on my I4 and through the lower radiator hose on the V6, Do it from the Hose, its so much easier and you don't have to worry about breaking that stupid cheap plastic crap that GMC calls a petcock
 

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Now that I have done drains through the petcock on my I4 and through the lower radiator hose on the V6, Do it from the Hose, its so much easier and you don't have to worry about breaking that stupid cheap plastic crap that GMC calls a petcock
Right you are.
In fact if you want to take it a bit further, as long as one side of the hose is loose and coolant is drained, get a new hose and ask yourself when was the water pump replaced last.
 

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+1 with the above. Don't touch the petcock and replace the hoses... water pump, etc as long as coolant is being drained and the vehicle is over 5 years old. . . it's just a good idea.
 

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Moving the petcock tab from horizontal, stops at vertical position and nothing comes out, have tried the following:
WD 40 though the spout and around the tab and move tab many times and also tried pulling out while doing so
Reservoir cap off.
Breather screw loosened and fluid weeping out.
Would really like this petcock to work without breaking it (Delco tab/insett costs $22 plus shipping), as a last resort will disconnect lower radiator hose.
Thank you.
 

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My plug looks like that but doesnt grab onto anything inside the rad to hold it in....how does it work or stay in there?
 
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