Questions Regarding Recent '96 Riviera (Supercharged) Purchase

[RedneckRAM]

Hello!

I recently purchased a '96 Riviera supercharged as a college commuter. It has 109,000 miles and was on non-op for the last two years. Previously, the owner's father had driven it and taken great care of it until he passed around a decade ago, and the son had put around 8k miles on it since his father's passing.

I've been chasing down a few issues and gremlins with the car since my purchase a few days ago, and catching up on maintenance since it sat for so long. My college commute is a fairly strenuous mountain highway, so I'd like to be proactive on the car's potential weak points. That said, I have a few questions I've come across and haven't been able to find too much information on:

• Is the supercharged 3800 from this year at less risk from the intake manifold gasket leak issue?
• Should I change the intake manifold gaskets just in case?
• Anything potential issues I should keep an eye out for with this engine?
• I've noticed a little smoke coming off the exhaust manifold, it neither smells of coolant nor oil. Any possible causes of this?
• Should I change the coolant from the old DexCool to yellow or similar non-DexCool coolant?
• Would it be worth changing the transmission fluid and filter?
• Can I safely run it on 87 octane gasoline, or should it run on premium?
• In regards to the interior, is the radio a standard double-din or an odd size? Anyone replaced theirs with a modern one? If so, any advice on how to do this?
• The cruise control is acting weird, it was working, then it quit and won't turn on again.
• The A/C and heater controls went wonky while driving around, and the A/C switched on the left side to heater, while staying cold on the right. I ran it up and down cold to hot a few times, and it seems to be working alright now. Was this caused by the blend door malfunctioning or just a freak electrical gremlin issue?
• There's a security light on the dash that stays on for about 10 minutes. Is there a reason for this?

Any wisdom would be greatly appreciated. I did quite a bit of research prior to purchasing it, but there's a surprising lack of repair information on these cars. Thanks in advance.

 

[LARRY70GS]

Riviera Performance

Riviera discussion board/forum. The member-shared knowledge base for the Riviera by Buick.

rivperformance.editboard.com

The above site is specific to the 95-99 Buick Riviera. It will be your best resource by far for these cars.

The supercharged 3800 is less at risk for failure of the lower intake manifold gasket (LIM). That is because the LIM is aluminum, not plastic. Still the stock gasket design is not good. The redesigned gasket using metal instead of plastic is much better.

More Information for FEL-PRO MS98014T

The 3800 engine is a really great engine. Other than the LIM gasket, they are pretty bullet proof. If you can change the gasket, I would.

If there is smoke coming off the engine it is either coolant or oil. My guess is the valve cover gasket(s). Pretty common for them to leak. I had a 98 Riviera that leaked oil a bit, it never smoked though. My engine also leaked a bit of coolant externally at one corner of the LIM, and I never changed the gasket, sold the car with 212 K on it in 2023.

I would change out the Dexcool to the universal type Anti Freeze commonly sold today. Make sure to flush the system completely. Not a big deal as the new stuff will mix with any coolant, but it is good practice.

Look at the ATF. If it is dark, I would change it. Even if it looks good, I would change it to get a baseline for future maintenance. The pan gasket is excellent and reusable. My 98's transmission was original and shifted great at 212K, I changed the fluid every 20K from 86K when I bought it.

The supercharged engine needs 91 octane minimum. If you drive it like a little old lady and stay out of boost, it might tolerate 87 octane, but I wouldn't. If the engine detonates under boost, you'll damage the pistons, and possibly the rod bearings. I would not take the chance.

Plenty of info about aftermarkeet radio selection here,

Audio & Electronics

Riviera discussion board/forum. The member-shared knowledge base for the Riviera by Buick.

rivperformance.editboard.com

The cruise control module is a common failure. It's on the firewall, follow the throttle cable back to locate it. Not sure about availability. Also check the fuse, and the brake light switch.

The climate control doors are operated by electronic actuators. They have plastic gears that can can crack, which seizes the actuator up. They are available on RA, and/or, you can take them apart and repair the gears.

1996 BUICK RIVIERA 3.8L V6 Supercharged Heater Air Door Actuator | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.

www.rockauto.com

Write-Up: HVAC Assembly

Thought Id put this out there just in case anyone else is having problems with their HVAC. The first picture is of the drivers side of the HVAC Module Assembl

rivperformance.editboard.com

The security light indicates a problem with the anti theft Pass Key system, and can prevent the engine from cranking to start.. It may have been bypassed by the PO.

security light - Write-Up: No Start + 3 min delay / Disabling PASS-Key II Security

security light My car has been sitting for two years, (1995 3800 super charged (sorry) I just recentely had an overhaul on the engine and some work done on t

rivperformance.editboard.com

 

[RedneckRAM]

This is all fantastic, thank you so much for the reply.
I'll definitely look into a LIM gasket change ASAP. I think I found a leak, as there's a small puddle between the injectors and the supercharger. It's also developed a gas smell sometimes, which I've been trying to look into as well.
I'm definitely going to have to prioritize this project, as it's a bit more than I was anticipating truth be told. It's such a comfortable and nice car, though. I've been genuinely impressed by the overall quality of it. Again though, thanks for the information. I just joined the Riviera forum you sent as well.

 

[LARRY70GS]

This is all fantastic, thank you so much for the reply.
I'll definitely look into a LIM gasket change ASAP. I think I found a leak, as there's a small puddle between the injectors and the supercharger. It's also developed a gas smell sometimes, which I've been trying to look into as well.
I'm definitely going to have to prioritize this project, as it's a bit more than I was anticipating truth be told. It's such a comfortable and nice car, though. I've been genuinely impressed by the overall quality of it. Again though, thanks for the information. I just joined the Riviera forum you sent as well.

You're Welcome.

If you remove the trunk liner, you will see an access panel for the fuel pump. You might want to look at that. The gas tank is plastic, and there are metal tangs that hold the fuel pump down with a locking ring. Those tangs can rot and the fuel pump to tank seal can be affected. That would result in a fuel smell. Hopefully that is not your problem. I would also check the fuel lines in the engine compartment near the brake booster. Make sure they are not leaking.