Potential catastrophic coolant loss due to HVAC coolant line rupture
Early 2001 Suburban 3/4 ton trucks have a serious manufacturing defect involving the frame mounted HVAC lines. I have not seen a recall on this yet, but one had better be on its way. The problem is with the set of HVAC lines that run the length of the truck on the passenger side. These lines run along the frame, past the rear wheel well, and up into the rear compartment. Just before the lines run up into the rear compartment, they pass against a frame member junction, just behind the rear axle, that acts like a saw blade, eventually cutting a neat slice in these HVAC lines. This frame member junction is not sharp (a bit less than 1/8 inch thick), but over time will rub through the lines that are mounted such that they are pressed hard against it.
It looks like GM has been trying to fix this problem since at least February 2001. There is a report that a May 2001 built truck has all kinds of spacers and rubber hold offs in this area to prevent the problem, so it looks likke GM has addressed this problem with a silent fix. There is another report that a late February 2001 build has HVAC lines that are enclosed in large diameter, split-plastic corrugated wire loom from the front all the way to the rear to the point where they turn up to go into the body. The two 2001's I looked at on the dealer's lot had not had this problem fixed, though i do not know the date of manufacture.
My luck ran out at 15,000 miles and took 2 weeks in the shop waiting for parts. The line that ruptured was the heater coolant line (another line was damaged as well), which effectively put the truck out of commission in the dealers back lot waiting for parts. As these trucks hit the streets last October (10/2000), now is about the time the failures will begin to be seen.
I do not know if coolant flows through these lines if the rear heater is turned off, but I have not used the rear heater for a quite a while (it still being hot and all) and noticed only a small leak with the severed coolant line. If coolant flows only when the rear heat is turned on, then in a few months when winter hits there may be a flood of Suburbans with coolant loss failures (no pun intended).
These replacement lines are not standard replacement parts (yet) so it took 2 weeks to get them in. Why 2 weeks? It appears that GM never thought the preconfigured 12 foot long HVAC lines would ever need to be replaced, so does not (did not?) have parts on hand for this problem. After all, its not like the lines will rupture as they rub up against a frame member junction for 15,000 miles would they? The dealer said he had recently completed this work on another Suburban and it was a 3 1/2 week wait for parts. What fun. I got no flak from the dealer on this repair, and without me even bringing the subject up they provided a free rental car for the 2 weeks my truck was out of commission.
The following photos show the area in question. After the fix, there is now a finger wide gap between the frame junction and the hoses, keeping everything out of harms way. The fix looks to be an added bend in the hoses to rout them away from the slicing ridge.
Photo 1 - Overview of the area around the rear passenger wheel well
Photo 2 - First closeup of the frame member junction
Photo 3 - Second closeup of the frame member junction