Coolant Leak

wstuckey1

Original poster
Member
Apr 11, 2018
457
Fenton MI
I have coolant leaking relatively badly from my EXT. I know it's related to the rear heater core because I had coolant dripping from the back right corner, but that leak has kind of gone away and now its leaking under the front passenger door, and in the cab. I don't know how it's getting in the cab but I noticed after my dune trip when the sand that was on the carpet absorbed a bunch of coolant. I pulled the passenger rubber floor mat and the carpet was soaking wet with coolant. It's somewhat spread around the first two rows of seating but the worst spot in the cab is the passenger footwell. I need to get this fixed soon so if anyone can tell me how to block off the flow of coolant in the engine bay before it goes past the firewall I would be super happy. I don't know if it's possible to remove the rear heat but keep the A/C, but that would be ideal for me. I saw someone on another thread mention it but he didn't know if it was possible either.
 

TollKeeper

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Member
Dec 3, 2011
8,047
Brighton, CO
It is possible. On the front side of your firewall, the 2 coolant lines will have a T before they go into the firewall, if you pull the lines off before that T on both lines, and feed them into each other, you will have taken out the rear and front heater cores.

One of those lines might have a coolant diverter valve instead of the T's. You want to take the feed line, and return lines off, and combine them.

This is what you can combine them with (I think its a 3/8 inch hose, cant remember for sure)
https://www.zoro.com/zoro-select-ho...3LPDuYe3yDwcaR1chPLOJZsEeysNY4-caAn3REALw_wcB
 
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wstuckey1

Original poster
Member
Apr 11, 2018
457
Fenton MI

TollKeeper

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Member
Dec 3, 2011
8,047
Brighton, CO
Correct.
 

wstuckey1

Original poster
Member
Apr 11, 2018
457
Fenton MI
I want to keep the front heat. I don't care about the rear heat. Easily 90 percent of my driving is just me in the truck, but I live in Michigan, can't do without heat in the front.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
This thread should help:

If you want to bypass that whole valve and rear heater core, you'll have to make the hose routing like the shorties, like the image from this post on the old site:

You might be able to cobble the existing hoses to work.
 
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TollKeeper

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Dec 3, 2011
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Brighton, CO
If your floor is soaked, I would think that the front heater core is also toast. Am I wrong in this?
 
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Blckshdw

Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
If your floor is soaked, I would think that the front heater core is also toast. Am I wrong in this?

I was thinking this too. Or at least one of those connections at the firewall, is leaking. The actual rear core, is in the cargo area.
 
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Reprise

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Jul 22, 2015
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Prolly been leaking coolant for awhile out of that front core. I'd be surprised if temp gauge didn't register it (I see you have the I6, so the reading is 'relative')

I have some info saved that Paul Bell gave yrs ago on the TBSS parts needed to block off the rear core at the firewall end, but I don't think it'll help you since it's really for V8s (PM me if you want it anyway)

If your wetness doesn't go past front of the second row, it's prolly frt core only. The rear one is behind 2nd row, psgr side. But do the rear removal too, once the blockoff has been effected.
 
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wstuckey1

Original poster
Member
Apr 11, 2018
457
Fenton MI
Prolly been leaking coolant for awhile out of that front core. I'd be surprised if temp gauge didn't register it (I see you have the I6, so the reading is 'relative')

I have some info saved that Paul Bell gave yrs ago on the TBSS parts needed to block off the rear core at the firewall end, but I don't think it'll help you since it's really for V8s (PM me if you want it anyway)

If your wetness doesn't go past front of the second row, it's prolly frt core only. The rear one is behind 2nd row, psgr side. But do the rear removal too, once the blockoff has been effected.
I'm thinking now that it's both cores.
 
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wstuckey1

Original poster
Member
Apr 11, 2018
457
Fenton MI
Update, I pulled the dash to replace the front heater core. Looks like it was perfectly fine. No obvious leaks or any coolant on the plastic around it. Right now the only other way I can see coolant getting in the cab is from the rear heater core so removal of that will hopefully start next week.
 
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JerryIrons

Member
Dec 20, 2011
434
I have an EXT, live near buffalo NY and capped off my lines going to the rear and have plenty of heat, just an FYI. Make sure you check the lines where they pass through clips, that's where mine went bad.
 

C-ya

Member
Aug 24, 2012
1,098
@wstuckey1 , I farmed my front heater core out when it was leaking. I could smell coolant and the passenger floorboard was wet. Surprising that that wasn't your issue.

My current problem is the rear A/C lines are leaking at the back. My solution was to buy a set of gauges and top my freon off until it dies. Prolly two more year if I can keep from rusting out from under me. They make a set of hoses to run along side the original ones, but for the price, my solution is cheaper. I like my front and rear heat and A/C!
 
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Reprise

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Since this thread is still ongoing, here's the info Paul Bell posted waaay back when. Maybe it'll be helpful. I also have two screencaps he posted of the area in the engine bay, if you want to see those.

Sorry - no part numbers below, but if you can find the relevant TBSS sections in the GM online catalogs...

(Paul's text below...)

It looks like the online catalogs call for a V8 vehicle to be an extended body with the rear heater so I've concluded that as the TBSS was a V8 with a short body, it can't have a rear heater so those are the hoses for me. It's a plug & play setup and has heat protection on the rear hoses, an ear to bolt to the valve cover and the nipple for the head bleeders.




89474
 
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