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 REPEAT RADIAL-4 FAILURES ON 1994-95 SUBURBAN   By Paul Weissler - Back to Index Page

Delphi’s Radial-4s may not be modern high-tech, and they’re not known for ultra-quiet operation. But after early teething pains, they proved to be reasonably durable.

Though they haven’t been in OE production for years, many vehicles on the road have them, so brand-new replacements are still being manufactured.

And some Radial-4s have been failing on 1994-95 Chevy/GMC Suburban with rear air, and more than one replacement per vehicle. It isn’t the compressor. The problem is that the compressor is being hit with liquid refrigerant, which when it’s pumped out, is taking oil with it. The root cause is a defective rear expansion valve.

Symptom: the compressor will get very noisy under low-cooling loads as a result. However, there are lots of other possible causes, so here again, is one example of why you need an accurate refrigerant charge in the system (we have another, later on).

There’s a straightforward way to check the rear TXV on these models, with a pyrometer on the suction line, (accessible behind the right rear wheel). Push back the rubber protective sleeve and clamp or tape the pyrometer probe to the suction line. Run the engine at idle, system in recirc, rear blower off and front blower on low-medium speed. After 15-20 minutes the pyrometer should read 32-34 degrees F., which indicates the expansion valve is working properly. If the temperature reading is 46 degrees F. or higher, the expansion valve is stuck open and allowing refrigerant flood back. Yes, we know this is time consuming, but did you just want to guess?

The fix: the better choice in an OE rear expansion valve has a straight capillary (Parker Hannifin Part No.52459601), and if it’s what you get, check the attachment (should be with two claws) and when you install, wrap with insulation and tape.

However, you may be offered a superseding part, one with a coiled end, for which a specific clamp is provided. However, the aftermarket grapevine says the accuracy of the sensing may not be nearly as good. Even unwinding it carefully may not provide an installation with as good and reliable sensing over the long term, according to those familiar with the parts. In addition, the clamp provided with the coiled-type would be unsuitable.

For the moment, back to the subject of refrigerant charge accuracy. If you don’t have an accurate charge in the system, those pyrometer temperature readings are meaningless. However, we’ve got a variation on this problem that really is something else: a total of six (count ‘emsix) compressors on a ’95 Suburban. It raises additional issues, including that rear TXV.

When the Suburban Radial-4 in one case repeat-failed, the shop didn’t check service bulletins. It thought all it needed was to solvent-flush the system and then install a (new) replacement. However, debris had blown back into the suction line and of course, it hit the new compressor and caused still another failure.

Compressors Nos. 3, then 4 and 5 were installed, apparently more with a sense of desperation than a willingness to step back and think. A look at the suction manifold following the 5th failure showed that no screen had been installed, and a look into the suction port of one of the failed compressors showed a chunk of debris wedged in.

Backing up a bit: with No. 4 had finally came a new rear TXV, one that had the same superheat rating but with the coiled capillary tube, and it was installed, but it wasn’t the answer.

Flushing also wasn’t doing the job on this front-and rear air system, and after the fifth compressor failed, hard thinking and looking turned up a debris-loaded screen on the rear TXV.

At this point, highly-experienced outside advice insisted on more than solvent-flushing and rear TXV screen replacement.

Although the coiled-capillary rear TXV may not have been the sole cause of another repeat failure, there was suspicion at least it had contributed. Installing the OE type with the straight capillary would likely produce an installation that senses more accurately.

The orifice tube (which had metal debris) was replaced, a suction side screen also was installed and an in-line filter was put in the liquid line. And yes, an OE rear TXV with the straight capillary was located and installed. Finally, the funerals were over. No. 6 lives! The 1994-95 Suburban are not a high-volume line of SUVs, but if you encounter the problem and need that type of OE TXV with the straight capillary for those Suburban, Global Air of Hollywood, FL (954-922-0053) says it carries a supply.



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