Hey guys,

I got a 1999 Pontiac Grand Prix GTP and upgraded to a 1-3/8" radiator. The radiator listed in this post will bolt directly in a Grand Prix with a couple slight modifications that anyone can do. The install is straight forward and easy, one of the those most simple mods you can do and one of those most benifical too, especially for you intercooled guys.

Here's what I got...

I went to my local O'Reillys Auto Parts store and got me a new aluminum Proliance Radiator PN: 432387. If for some reason they cannot access this PN (they should have no problems) the radiator is for a 1998 Chevy Monte Carlo, 3.8 Liter V6 N/A, and there will be 3 choices for the radiators... a 5/8", 1", and a 1-3/8" HD listed on the computer. If its not in stock it'll most likely be at the local HUB, you should get it the same day most likely. Before buying the radiator, take you tape measure and double check the core size! The first one they got for me was 1", but the sticker had the correct PN on it. They got another one and it was correct, double check this before purchasing! The radiator cost me $186.99 and w/ tax that came out to $202.65. It comes with a LIFETIME Warranty which is worth its weight in gold IMO. If something fails on it, a replacement is a few hours from me at all times. This is important to some people, especailly those with daily drivers.

I just did a write up on how to install/modify it to fit here: http://www.grandprixforums.net/f73/c...rade-3697.html (Cheap 1-3/8" Radiator upgrade for your 97-03 Grand Prix [*])

Don't go with stock when you can get a nice upgrade for the same price and only need to do very minimal and painless modifications.

Hope you guys enjoy this upgrade!

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Shawn W. Larsen

Good find, the community thanks you

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2002 GT...Wizardair, ZZP 2.5 o/r dp, Special Eddition two-tone leather interior added, HUD added, 12" Brake Upgrade, ZZP strut tower bars, gmpp sway bars,-6an braided SS fuel hoses , Hptuned, Top Swap in, just waiting for harmonic-balancer
Car Pics Here: http://s266.photobucket.com/albums/ii280/Dough523/

Actully thank Rook (i think thats his SN?). He told me about it, i'm now telling everyone else about it + did a write up

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Shawn W. Larsen

This is an awesome upgrade, but I do have a question. The part number you list shows as only 1" thick...is the information wrong, or maybe you have the number off?

Proliance Online Catalog

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2000 NavyBlueMetallic GTP Coupe 14.007 @98.5 - New time coming soon!
HPTuners / Intercooler / 1.8 SLP Rockers / 3.1" / 180° / TB Shield / FWI / PLOG / Jimmy-C Downpipe / U-Bend Delete / Taurus Fan / Alt. rewire / FP rewire / F-Body Brakes / Buick Strut Braces / SLP Tips / 20% Tint

I double checked everything, the number above is correct and according to OReillys the PN above is for the 1-3/8". I donno which is wrong. I know for a fact mine is a 1-3/8" (measured it) and it has that PN on it. I donno, somebody is wrong... OReillys or Proliance...

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Shawn W. Larsen

But you did measure the fins specifically at 1-3/8"?

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2000 NavyBlueMetallic GTP Coupe 14.007 @98.5 - New time coming soon!
HPTuners / Intercooler / 1.8 SLP Rockers / 3.1" / 180° / TB Shield / FWI / PLOG / Jimmy-C Downpipe / U-Bend Delete / Taurus Fan / Alt. rewire / FP rewire / F-Body Brakes / Buick Strut Braces / SLP Tips / 20% Tint

Yes the core is 1-3/8", not measuring the side tanks, i'm measureing the core itself (what you're suppse to measure). My stock GTP rad was 1", my new radiator is 1-3/8" with PN 432387 on it. Measured everything about 3 times before doing anything.

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Shawn W. Larsen

Just called OReillys. I had them look up a 1998 Monte Carlo, 3.8L... They of course had 3 radiators listed, here is what they had for part numbers for that car...


5/8" Radiator = 432426
1" Radiator = 432427
1-3/8" Radiator = 432387 <------------(The Radiator you want.)


Since something ain't right somewhere, heres what I recommend. Go to your OReillys store, look up radiators for a 1998 Monte Carlo 3.8L, they will have 3 choices of radiators and they should ask you what size do you need. Ask for the 1-3/8". Whenever they get it to you, before buying it or taking it home, measure it. Take a tape measure with you and mesaure the core itself to ensure you get the correct core for your application. If your core measures 1-3/8", you're good to go.

Good Luck...

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Shawn W. Larsen

Awesome, thanks for the footwork on this Shawn!

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2000 NavyBlueMetallic GTP Coupe 14.007 @98.5 - New time coming soon!
HPTuners / Intercooler / 1.8 SLP Rockers / 3.1" / 180° / TB Shield / FWI / PLOG / Jimmy-C Downpipe / U-Bend Delete / Taurus Fan / Alt. rewire / FP rewire / F-Body Brakes / Buick Strut Braces / SLP Tips / 20% Tint

Rockauto has 432387 listed for $147.79. Throw in the 5% discount and it is down to $140.40, and the shipping to me zip code was $12.45.

PartsAmerica has it for $145, which means you can probably get it at your local Advance Auto Parts / Checker Auto Parts / Schuck's Auto Supply / Kragen Auto Parts / or Murray's Discount Auto Parts stores.

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2000 NavyBlueMetallic GTP Coupe 14.007 @98.5 - New time coming soon!
HPTuners / Intercooler / 1.8 SLP Rockers / 3.1" / 180° / TB Shield / FWI / PLOG / Jimmy-C Downpipe / U-Bend Delete / Taurus Fan / Alt. rewire / FP rewire / F-Body Brakes / Buick Strut Braces / SLP Tips / 20% Tint