Coolant leak

WarGawd

Well-Known Member
#1
Did some cursory searching before posting but didn't find anything yet. Figured I'd dash out a quick post while I carry on.

I've developed a coolant leak in the engine bay, somewhere slightly forward of and below where the lines connect to the heater core at the firewall. Curious If anybody has any good pics of the area, layout/routing diagrams, or any knowledge of common spots where rust/corrosion/stress etc cause leaks.

Thx guys :smile:
 
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WarGawd

WarGawd

Well-Known Member
#2
I'm probably gonna bring it to a DIY shop where they rent hoist space by the hour. Hoping I can find a leak that I can splice in a section of heater hose like I did with the leak on the return line from the rear heater core last year...1 ft of 5/8" heater hose and a couple hose clamps has worked good since. Any info on the line diameters up front would be useful too, just so I can guess whether I should grab say some 1/2" hose before I go there.
 

MRRSM

Lifetime VIP Supporter
#3
Here are two images of that area (with the Engine & Transmission Pulled on a Blown Motor) that will illustrate where the Work Area is... and if you look closely ...you can see that Short Pipe to Rubber Hose connecting into the Passenger side of the Engine Block... that entire section of Hose can be replaced as once piece and then you can attach the replacement Dorman Male & Female Black Plastic Connector Set where it mates up to the Heater Core Piping at the Right Firewall.

It will be necessary to salvage the Silver Heat Insulator Sleeve for re-use or obtain some Shielding Aluminum-Fibre-Glas Tape to surround-wrap those sections of Heater Hose... otherwise, the High Radiant Heat Energy from the Exhaust can destroy that New Hose Line over time. If you look up the Dorman Hose M2F Connector Kit(s) on RockAuto ... they will provide the hose dimensions of that coupling.

You will also need to also obtain a packet of Stainless Steel Screw Vernier Style Hose Clamps for this exchange. Please know that there are TWO distinct Kits for each of those individual Heater Hose lines that are NOT indentical and comprise a whole lot of sub-components to make the OEM HH re-attachment work. Hope this helps...

HEATERHOSECONNECTORS.jpg


.HEATERHOSECONNECTORS1.jpg
 
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#4
You have an XL? That means you have extra hoses and a valve for the rear heater core. Could also be the front core leaking out of the same drain as the A/C. The connectors have o-rings that could be leaking. Not sure if just the o-rings can be replaced or the whole connector has to be replaced. Lots of places for leaks.
 
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WarGawd

WarGawd

Well-Known Member
#5
Thx guys

In the hoist at DIY shop now. @Mooseman is correct...the XL has rear heater core. @MRRSM, as far as i can see it is not the short hose that leads to passenger side engine block. The other heater line runs vertically, parallel to an ac line. Just above where the line meets the frame rail, there is one of those GM quick connect couplings to transition from rubber to metal line. The condition of both the rubber and aluminum line sections in the vicinity appears to be solid...my inclination at the moment is the connector/o-rings as alluded to by @Mooseman .. I'd like ti disconnext and examine that connector...need info on how those connectors work and whether rings are replaceable etc

Thx as always guys...watching for updates on my phone
 

Reprise

Lifetime VIP Supporter
#10
Quick google search suggests 15/16" outside-diameter, with a thickness of 3/32" on the o-rings.

This was from a '95 Burb with rear heat - while not an exact match, I'll guess the HVAC hoses / connectors are the same diameter, across GMT lines of that vintage.

And the OP's latest post just now seems to confirm what I guessed, which was heat expanding the connectors, and the o-rings losing their sealing capability. If you get the connectors off, dig out the o-rings and find them brittle, that's probably (?) what has happened

(and there *is* a special tool, which kinda defeats the term 'quick disconnect', but I digress)
 

Reprise

Lifetime VIP Supporter
#12
NP. Here's the page I got it from, if you're curious. Good luck!
 
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WarGawd

WarGawd

Well-Known Member
#14
It does offer some insight yes :smile:

I had another question or two for you guys as well -

I think the connector that's leaking is the supply line to the rear core. The leak itself has been variable since it started, sometimes minimal and sometimes more significant. On reflection, it seems like there may be some correlation with whether or not rear heat is on (it rarely is, but sometimes I bump that switch on the console and turn on the rear fan without noticing).

In post #4 above Mooseman refers to a valve for the rear heater core. How is the valve actuated? Is coolant flow intended to be positively shut off to the rear core when the valve is closed, or is it just "mostly off"? Where is the valve situated? Is it possible to manually close the valve or block the supply side flow of the coolant to the rear core as a temporary stop-gap measure?

I'll be searching for this info as well, will post if I find it before someone else spends time typing for me.

Thx again as always :smile:
 

MRRSM

Lifetime VIP Supporter
#15
The variability in how much or how little it leaks Fluid might depend upon whether or not you are observing the issue from a "Cold Start" when the Aluminum Piping and or Plastic Couplers have had the chance to contract with the Cooler Temperature... or later on after they expand dramatically as the Engine Block Heats up and the thermal signature into and out of The Heater Core to optimizes the transfer of the abundant thermal energy of combustion manages to soak into the Coolant Column.

I suppose the idea is that the Two "O" Rings ordinarily nested in between the clamped connections are supposed to compensate for this difference. But as we all know... Plastic components... no matter how robustly molded and tightly 'specked'... can become 'work hardened' from vibration and radiant energy attacking them from the inside as well as from the engine compartment heat.

As such, just like all Metals... they will become Fatigued and Crack over time. As for the "O"Rings inside... even with Two of them in place to do 'Double Duty' while sealing up the two locations... as the Heater Hoses move around and Gyrate Dynamically from Engine Vibrations and the normal motions of driving around... they will invariably wear out internally and flatten out. Eventually, they lose enough of their "Plumpness" to allow fluids under High Heat Expansion and Internal Pressure to defeat them as well.

GM would like to think they've created something here that is Pure Genius because of all this excessive 'over-engineering' instead of simply using Barbed Nozzles made out of Solid Brass and employ Spring Steel Clamps that may be a PITA to get on and off... but will NEVER fail until the Rubber Hosing literally rots away. The object of this game here is ensure they eventually achieve enough "planned obsolescence" in order to get your SUV/Truck up on their Dealership 'Lift" ...while their GM Service Manager tries to "Lift" your Wallet.
 
#17
Sorry I'm late to the party. Was my wife's b'day :smile:

That would be #23. IIRC, it's vacuum and electrically actuated. That's why EXT/XL are the only ones that use that vacuum port on the front of the intake.

I never used a special tool to remove those. Squeeze the two tabs and pull is all I ever did. Might have used pliers.

My EXT's rear heat never worked despite replacing the rear core due to failed actuators and really not missing it. Maybe yours starts leaking when the rear heat is activated and flows coolant to the rear. Maybe you could just bypass it or figure a way to plug the two lines that go to the rear, unless you want to keep it.
 
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WarGawd

WarGawd

Well-Known Member
#18
Thanx for that...very helpful. Which model year is this representative of? As I understand it, in later years GM added a fluid flow booster pump for the rear heater core, which doesn't seem to be depicted here. But if the HCV is indeed located right on the firewall by the heater core and that bottom nipple is the feed for the rear, it looks to be just connected with one of those spring steel hose clamps... might not be horribly difficult to pop it off and cap the nipple & plug the open end of the rear heater supply line till say March or April when its warm enough to work on and I've had a chance to source the connector or o-rings.

Happy BD to your wife Moose. Thanx for the extra feedback...you have the right general idea...cap and plug for now but repair when warmer so I can preserve that function if possible.

Off to bed, work early - thx again folks
 
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WarGawd

WarGawd

Well-Known Member
#20
Thx @mrwitty_1 - mine is listed in my profile, 05 Envoy XL SLT... but it was built IIRC Oct '04 and as far as I can see the plumbing on mine is in agreement with the diagram.

Found the connector 15139564 at local dealer for $17.60 so I'm not even gonna bother trying to find other solutions.

Thx for all the help guys... I'll mark this solved once I get the connector R&R'd :smile:
 
#23
I have a traiblazer ext, and had a hard to find coolant leak, at least until the hole got big enough to leak a lot more than you are used to and almost overheating the engine. It was a line that runs to the back heating system, along the frame and tucked up high. Kind of like the way the AC lines corrode near the clips. I capped off my lines, we never have people sit in the 3rd row seating and have never missed it, even near buffalo NY winters.
 
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WarGawd

WarGawd

Well-Known Member
#24
@JerryIrons yeah that was a problem for me last year. I wanted to preserve the rear heat...dealer was quoting like $1500 to replace the faulty line. After a while of living with the problem and investigating cheaper alternatives etc. I just cut out a section with my Dremel and double clamped a piece of 5/8" heater hose in its place. It's been great since and cost me all of like $20 and a couple hours of labor... at 400,000 km, I expect some wear and tear and aging will require maintenance - but I'm not ready to give up on it yet :smile:

Lower control arm support brackets on the list for 1st spring project....
 
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WarGawd

WarGawd

Well-Known Member
#25
Thx @mrwitty_1 - mine is listed in my profile, 05 Envoy XL SLT... but it was built IIRC Oct '04 and as far as I can see the plumbing on mine is in agreement with the diagram.

Found the connector 15139564 at local dealer for $17.60 so I'm not even gonna bother trying to find other solutions.

Thx for all the help guys... I'll mark this solved once I get the connector R&R'd :smile:

So I thought I should do a quick update for future readers - It turns out that Item # 3 that I tracked down to P/N 15139564 using the '03 diagram was slightly off. Somehow the callout that I looked at only had that part number.

It arrived at the dealer yesterday, and on inspection today I found that the part is actually a 90 degree elbow, not the straight connector as depicted in both diagrams. With help from the guy at the parts counter, I found that the callout diagram for my '05 XL actually crosses to two part numbers - 15139564 for the 90 -degree variant, and 15139175 for the straight variant.

So I rejected the 90 today and got the 9175 on order, which now comes from Montreal instead of a lengthy wait for shipment from the U.S. :quiverlips:
 

MRRSM

Lifetime VIP Supporter
#26
Do you have to do anything exotic in the way of a need to remove any other components to either gain access and work from the Top-Down ....or from the Bottom-Up to effect this repair? If so... more images of the B4nAFTER would be "The Cherry on The Cup Cake" :>)
 

Bill Reid

Well-Known Member
#27
FYI and FWIW,
I just did my firewall hoses on my 06 TB SWB 5.3. I had one leaking at the firewall connection and wound up doing both hoses. BTW, in my application, GM no longer offers OEM replacements (completed hose assemblies).

I used Dorman quick disconnects... and ordered them through Amazon. The common theme was 5/8" heater hose (for my application)... and bought 3ft of it from O Reilly's but needed slightly less. I bought 1/2" wide hose clamps from Home Depot and I believe the range of the clamp was 3/8 to 7/8. They work perfectly.

Here are the Dorman parts:

800-419 (3/4" pipe to 5/8" hose 90 degree fitting)
800-416 (5/8" pipe to 5/8" hose 90 degree fitting)
800-403 (5/8" pipe to 5/8" hose straight fitting)
800-404 (3/4" pipe to 5/8" hose straight fitting)

I believe Dorman also sells other sizes...

As stated earlier these connections require no special tools...

... and I just went out and looked at my 03 TB I6... same style quick disconnects. The I6's have more odd molded hose curves than the V8 but looks like they could, perhaps, still be replaced with off the shelf hose. If not there are usually quite a few molded hoses behind the parts counter that might be able to be used... just need to look.
 
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