The most common mistake a buyer can make is not checking the build sticker. This is how you know if you are actually purchasing a true GN or a regal turbo clone.
If the car is indeed a manufactured Grand National the RPO line will start with option WE2.
Other than that first part here are my usual checks: (it gets a little lengthy)
BODY – Stock paint is a lacquer type and the ‘87 cars had a thin clear coat over the color which could fog using certain waxes. Any paint that looks “too good” for it’s age is suspect, since these cars had characteristically poor paint jobs from the factory. There was, in fact, an unofficial recall on late 80’s GM paint jobs. On 2dr coupes, look for cracks or waves by the top of the pillars which separate the front doors from the rear windows. These are caused by the body flexing from Buick torque! Rust is prevalent on the bottom of the passenger doors, in the bumpers, and under the rubber of the gas tank straps.
ECM – If you have access to a scan tool such as TurboLink™ , check for stored error codes. EPROM changes are very common in these cars, so ask the owner if the original is available. You will check for stored error codes again after your test drive. Jumper across the diagnostic pins and the following should activate- low speed fan, SES light, IAC motor, wastegate solenoid. The ECM itself is located behind the kick panel on the passenger side foot well. Abnormal wear, fit, or missing clips in this area can reveal frequent EPROM changes.
IGNITION – Examine the spark plug wires, since they tend to break down quickly from heat. Aftermarket wires aren’t always better. The coil pack and ignition module are also subject to thermal decay, and most people prefer genuine AC Delco replacements for these and most electrical components.
TURBO – The stock turbo is a Garrett AiResearch unit. Access the turbocharger inlet (compressor) side by removing the air intake (MAF) hose. Spin the compressor wheel shaft- it should move VERY easily. Examine it for any visible “play” and check the fins to see if they are damaged, shaved at the ends, or can touch the bell housing. Either is bad news.
Remove the intercooler hose from the turbo outlet (intake tube on non-intercooled models), and check for wet or caked oil in the outlet tube area and the intercooler. Buick placed a metal tube from the passenger valve cover to the turbo inlet, however many people cap the inlet and put a breather on the valve cover. If this “bypass” modification has been done, there should be no oil in the turbo outlet tube (unless it’s leaking from the turbo bearings!). If not, it is likely this area will be wet, because oil is inadvertently drawn in through the metal tube.
If you can, measure the wastegate actuator rod length. You must remove the rod end from the wastegate lever by releasing the c-clip. Be careful, since the clip tends to spring off suddenly. The stock rod is fixed in length at 5 1/4". Any shorter indicates the turbo is likely set for higher boost than stock.
Due to the excessive heat of the turbocharger, synthetic oil and/or frequent changes (<3000 miles) are recommended for these cars. Ask for documentation of this and all other service!
INTERCOOLER – The 84/85 series TR’s were not factory-equipped with intercoolers, but the 86/87’s were. The stock location is between the radiator and the crank pulley. The stock connecting hoses were thin black hoses with stainless bands to hold them on. Most aftermarket replacements are blue or black, much thicker, and may have a stainless weave on the retainer rings. Look for a tag on top of the intercooler marked “Garrett” with a serial number. Common aftermarket upgrades include extending the stock intercooler or replacing it with a larger unit behind the front grille. Any aftermarket or home brew intercooler should be examined for workmanship.
EXHAUST – Stock design is 2 1/4" with one “crossflow” (one-piece with 2 pipes in/out) muffler and slant-cut tailpipe ends exiting the sides. The stock tailpipes never exited the back under the rear bumper. Check the driver’s side header for cracks, especially between cylinders 5 and 3.
TRANS – The stock transmission is the 4-speed Turbo Hydramatic 2004R. Check the TV valve adjustment at the engine throttle body- the throttle plate should be able to travel a full 90 degrees. If not, the shifts may be artificially firmed up by over tightening the TV adjustment. A healthy transmission with stock shift points allowed a firm (but not harsh) shift pattern. Any “slack” feel between shifts could indicate a problem. Remember this on your test drive.
REAR END – Check the travel of rear axle by examining the pinion snubber, a short rubber stopper above the differential. The stock snubber is about 1 inch long and should show very little evidence of contact. Aftermarket snubbers, however, can be a few inches long and are expected to contact the differential housing. Since the rear end gets the brunt of the torque, check carefully for cracks and broken welds. While you’re down here, also look for little rubbery fragments embedded under the bumper and wheel wells. They come from the local race track.
All TR’s came with 3.42:1 gearing stock. Positraction was available but not standard. For more info on codes, check the rear end code page. In spite of the RPO Codes, beware of foul play here- it’s possible for people to swap the GN rear end components for lessers. The 8 1/2" limited-slip differential is the most desirable
OIL – check oil level. When you wipe the dipstick, there shouldn’t be a metallic tint to the oil on the rag!! Stock oil filter is the AC Delco PF-47, however the taller PF-52 is acceptable and has greater area of filtration. Any other filter may lack the anti-drain back feature of these two AC Delco models.
FLUID LEAKS – Check under the car for leaks of any kind. Most TR’s leak some oil from the rear main seal area, which will show up as wetness on the flywheel cover. Leaks are also common around the oil filler tube on the driver’s side valve cover. This leak can run down the back of the engine and mimic a rear main leak. Note all existing leaks and dry them off well with a rag. After the test drive, you will re-examine them to get an idea of how bad they are leaking.
BRAKES – the 86/87 TR’s use the much-maligned Powermaster brake setup. Check for a gray switch on top of the master cylinder to make sure the brake recall was performed. The stock (and very dangerous) pressure switch was all black. The large round ball on the system is the accumulator. If there is a yellow warning tag on it, it was likely replaced at some time- this is common. See the technical article at for more information on Powermaster testing.
TIRES – Stock size for the Turbo Regal’s are 215/65/15 on 15 X 7 rims. Larger or smaller may affect gearing, rub on turns etc… Remember this on your drive test.
I realize that might have been a little more information than you were looking for, but these are great cars and I would hate for you to be looking at a dud.
Goodluck, and let us know how it goes!!