Coolant leak, need help. 1998 GMC K1500 Suburban Vortec 5.7

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tinfoil_hat

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I had a block heater like that on my old Suburban and I loved it. Of course I drove off with the extension cord still attached several times. Once I was 20 miles from home and this car was trying to get me to pull over. Looked in the rearview and saw 50' of yellow extension cord following me.
The plug end might be ziptied behind the grill or right behind the front bumper. That's where you usually find them.
As for the block drain plugs, there are two. On the passenger side it is also the knock sensor. On the driver's side it looks like a 7/16" hex head bolt. It's gonna get messy when you pull the plugs. Coolant goes everywhere. On my current truck I removed both plugs and nothing came out until I roto rootered around inside with a piece of wire. Then a ton of rust and solidified Dex Cool shot out before all the water. Wear goggles and keep your mouth closed.
The plugs are pipe thread so clean them with a wire brush and paint them with PTFE sealant before reinstalling.
 

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As for the block drain plugs, there are two.
In terms of pulling the block heater to fix that leak, he only has to pull the one on the same side as the heater. There will be "somewhat" less mess if he drains the radiator first--assuming there's a radiator draincock. Otherwise, drop the lower rad hose off the radiator.

If it was me, I'd pull both, and do a complete coolant flush. Replace radiator and heater hoses with new, as required. Refill with extended-life coolant and distilled water. As said, I tend to put brass plugs or brass draincocks back into the block once I have removed the stock iron/steel plug(s).

On the passenger side it is also the knock sensor.
Yes. The knock sensor needs sealant on the threads, and it gets torqued to spec. when reinstalled.

On the driver's side it looks like a 7/16" hex head bolt.
I'd have said 9/16 hex.

It's gonna get messy when you pull the plugs. Coolant goes everywhere.
Yup.

On my current truck I removed both plugs and nothing came out until I roto rootered around inside with a piece of wire. Then a ton of rust and solidified Dex Cool shot out before all the water. Wear goggles and keep your mouth closed.
Yes. Common to pull the plug/knock sensor and have nothing come out until you poke around in the hole with a screwdriver/awl/pick and puncture the crust of sediment.

The plugs are pipe thread so clean them with a wire brush and paint them with PTFE sealant before reinstalling.
Yup. Given a choice, I use Loctite PST. There are several part numbers, the common one--easiest to source--is Loctite 592. 565 and 567 are also good. And there's a waxy "stick" like Chapstick version of that sealer, too. All of these have a chemical "hardening" agent--somewhat like thread-locker, but easily-disassembleable.

www.amazon.com/dp/B0002KKTH2/?coliid=I2C34IAJPLZFEQ&colid=2VLYZKC3HBBDO&psc=1&ref_=lv_ov_lig_dp_it

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Schurkey

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If I understand correctly I could just replace the o ring as long as the metal is not corroded to badly?
Yes. The metal is generally brass or stainless steel, they don't tend to rot. But anything is possible. And verify that the core-plug hole it goes into is not damaged/scored/gouged.

The heater itself will have a "V" retainer that spreads apart when the center screw is tightened. You'll have to back-off that screw (not enough to totally remove the screw, or lose the V-retainer inside the engine block) and pop the heater out--which involves kinda bending that V-retainer so that it clears the hole. The heater element HAS to be clocked in a certain direction, make sure you put the heater back in, in the same position it is now.

The center screw has it's own seal; if that's bad, you need a new heater or install a core plug.

Sometimes it's best to buy the new heater, have it handy...and return it if you salvage the original.

I didn't know that was a thing!
I'll have to get underneath and have a good look. What does that plug look like? Is it just a large hex bolt, or???
Look in your photo. The block drain plug is visible on the block, behind the recessed area of the U-joint for the driveshaft. (Below the hanging material on the block heater cord.)

9/16 hex head.

If I understand correctly I could just remove that drain plug and get most of the coolant out and avoid the worst of the glycol shower?
I'd drain the radiator first.

Will that drain the heather core as well?
Yes. It will drain that side of the engine block, and everything above the water pump. It will not drain the other side of the engine block, you'd have to remove the knock sensor just ahead of the starter motor for that. And it won't drain the radiator below the level of the waterpump.

Is flushing the system necessary? Or can I just refill the coolant and call it a day?
How old is the coolant?

If there's any question about coolant condition...this is the time to take care of that, along with the hoses, thermostat, water pump, radiator, heater core...anything coolant-related.
 
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El Tigre

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Had occasion to remove driver's side plug. Installed 1/4"NPT to AN-06 fitting in it's place along with a hose leading to a capped ball valve under engine for future use (and,I have)...
 

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^^^Nice.

Brass draincock ahead of starter motor/heat shield, with 3/8 hose attached to "aim the drainage".
Engine is in my 'Camino. Photo is ancient--probably thirty years since that trial-assembly.
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Poor photo, but brass plumbing for coolant drain on my boat 454 is visible on right side of the toilet-paper bypss oil filter:
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Nice98chevy

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That looks like a factory block heater. See if there is a flat bladed screw in the middle. If so, carefully try turning the screw to see if that tightens it up. I had the same issue with my 1998.
 

thx1138v2

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That looks very much like it but the wire looks like it is two prong 12v ( i could be wrong, I'll have to unplug it and see.) and not 110v. The wire leads into a large bundle of wiring harness and who knows where from there. Could have the previous owner removed the 110v cable? If so where would i look for it?

My google-fu seems to be lacking whit this one, I couldn't find any info about this exact thing.
I can only see 110v plugs that look similar but that's it.

Do I need to drain the coolant if I were to try to remove it to see what it is?

As for temperatures, it can dip bellow freezing here and most likely freezing when I'm out hunting. Does that matter?

Thank you.
Two things: 1) check the wire to determine if it is wet higher up, i.e. the coolant is running down the wire and so the leak is higher up also. 2) I did an Excel spreadsheet on water temperatures and freezing/boiling points. Your droplet looks green so I'm guessing you have coolant in the system. If it is 6o% to 70% you will be good to about -60F. Here's a link to an image: Temperature chart
 

BC K1500

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I just want to thank everyone for sharing their knowledge and helping me figure this out.
It is a nice forum whit fantastic helpful people!
I think I have all the details I need to fix this issue. Ill be doing it in a few weeks (Unfortunately my daily driver developed a problem I need to fix before I can get to my suburban:rolleyes:).

I will report back when I'm done, hopefully everything goes smoothly.

Thank you!!!


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BC K1500

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Two things: 1) check the wire to determine if it is wet higher up, i.e. the coolant is running down the wire and so the leak is higher up also. 2) I did an Excel spreadsheet on water temperatures and freezing/boiling points. Your droplet looks green so I'm guessing you have coolant in the system. If it is 6o% to 70% you will be good to about -60F. Here's a link to an image: Temperature chart
The picture is not the best but it is clearly coming form the heater, the wire is dry.

Thank for the temp chart, I was just going to use 50/50. Wont need anything more.
 
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