Should I replace my OEM thermostat?

So, I can stay with my Un-Drilled 180* Stat and not worry about the cold winters and thermal shock.?

Rickw wrote:

So, I can stay with my Un-Drilled 180* Stat and not worry about the cold winters and thermal shock.?

Can't say as to the shock with your fancy-ass stat...

But I would say that you can drill 1 or 2 1/16" holes and not worry about the cold winter warmup.

Recently I've noticed my 5+ year-old 180º thermostat unit ($5 AutoZone) has become stuck open. There were no serious warning signs of this, in fact during the summer and fall months I didn't notice it at all, as coolant temps were in the normal 175-180º range. As the weather turned colder, I can see the engine warms up only to about 160ºF and stays there. Before, the normally functioning unit would warm up to 185º, then fall slightly as it opened, about 5 mins into the warm-up cycle.

So now I'm in the market for a new 180º unit. Since t-stat prices max out at about $20, and most around $10, I thought I'd do some research and install the best I can find. Hopefully you guys can help steer me in the right direction. Honestly, I am perfectly happy with how the older unit performed, but as with any part replaced on the car, I want to make it an upgrade if possible. I'm noticing the balanced t-stat designs seem to indicate better performance, and haven't found any quality issues.

Here are a few models I've found that fit the Riviera:

• AC DELCO 12T4D OE (Alt 180º) 12-month/12,000-Mile Limited Warranty $6.01 (Amazon)


• STANT 431-13008 180º Stainless Steel, ELAC heat motor $2.95 (Summit)


• STANT 431-13358 180º Stainless Steel, ELAC heat motor $4.95 (Summit)


• STANT 431-13848 Regular Stainless Steel 180º (1 23/32" x 13/16" x 25/32") $4.95 (Summit)


• STANT 431-35848 Stainless steel 180º $5.39 (Amazon)


• STANT 431-45848 Premium, V-notch, 180º Superstat (1 23/32" x 29/32" x 29/32") $5.95 (Summit)


• GATES 33428 Regular 180º Reverse Poppet (1 23/32" x 13/16" x 25/32") $7.24 (Amazon)


• GATES 33428S Premium 180º (1 23/32" x 29/32" x 29/32") $5.19 (Amazon)


Something gives me the idea Gates and Stant are the same?

• SUMMIT Racing SUM-360180 Stainless Steel/Copper/Brass, 180º, High-Flow $7.95 (Summit)


• HYPERTECH 1018 Power Stat, 180º High-Flow, Stainless Steel $4.95 (Summit)


• HYPERTECH 1019 Power Stat, 180º High-Flow, Stainless Steel $9.95 (Summit)


• MOTORAD 239-180 Copper case 180º, Offset design, air relief $11.25 (Amazon)


• Motorad 7239-180 Failsafe (locks open) $15.47 (Amazon)


• JET Performance 10115 Powertech 180º High-Flow Stainless Steel $10.46 (Summit)


• JET Performance 10170 Powertech 180º High-Flow Stainless Steel $12.71 (Summit)


• WILSON Manifolds 557180 MotoRad Failsafe, High Flow 180º $15.75 (Summit)


• MR. GASKET 4364 Copper/Brass 180º Performance High-flow $13.95 (Summit)


• MILODON 16401 High-Flow 180º, Stainless Steel, "Balanced Sleeve" Design $13.95 (Summit)


• EMP/STEWART 301 (modified RobertShaw) "Balanced Sleeve" 180º Drilled, High-Flow, Copper/Steel $14.88 (Summit)


• EMP/STEWART 308 (modified RobertShaw) "Balanced Sleeve" 180º High-Flow, Copper/Steel $14.88 (Summit)


• FLOWKOOLER/ROBERTSHAW 330-180, 51211.51 BALANCED, High-Flow 180º, Copper/Brass $12.99 (Quadratech)


Assuming Milodon, EMP/Stwart, & Flowkooler/RobertShaw are all basically the same unit.

An odd ball 170º I found from a respected brand:

• MEZIERE Enterprises WN0070170 Standard Flow 170º, Copper/Stainless steel $16.25 (Summit)

I haven't got a clue as to which one is best, but I use the STANT 431-45848 Premium, V-notch, 180º Superstat

HAPPY NEW YEAR !!!

Over the years I have come to trust Stant and Robertshaw.

I installed a Stant 180* from napa (not sure which model #) when i first got my car 100,000miles ago. Still seems to be operating fine still.

Im not sure you would see any difference between any of them, especially since you didnt see much difference when yours was working vs stuck open.
However, from the pictures i would venture to guess some can flow better than other when open, though i dont know if even the worst one can underflow the WP and system at 15psi.

Good point. Maybe I'm looking into it too much. I may just get another Stant (I think that's what I have now), or I might try a few and compare results.

One thing that's odd: some of the units (including RobertShaw) that I listed from Summit show they work for GM 3.8L/231cid V-6, but NOT after 1986. Anyone know what changed after '86 that would exclude later years? I found a clue at the turbobuicks board:

"Good news, sort of. Yes, the Robert Shaw/ Mr Gasket 330-160 thermostat can be cut down to fit the 86/87 motor. Bad news. It may not work very well.

I spent this afternoon playing around, and ground down the lip on a old RS 330-180 stat to 1 3/4", to fit inside the manifold. It fits really well. (And is still very solid)

Here is the problem: The body diameter (part that moves) of the stat is 1 9/16". The ID of the inner step of the manifold bore is 1 11/16". The wall thickness of the manifold casting where the stat seats is 1/4". The stroke of the stat is 3/8"

So since there is only 1/16 clearance between the stat body (part that moves) and the housing bore, not a lot of flow will happen until the stat is almost fully open. 1/4" of 3/8" stroke upon the initial opening, is restricted by the casting thickness, so that leaves 1/8" of unrestricted flow when the stat is fully open, kinda defeats the purpose."

Link: http://www.turbobuicks.com/forums/buick-v6-turbo-tech/5383-robert-shaw-thermostat.html

So at this point, I am starting to wonder: A) if the RobertShaw would even fit, and B) would it operate correctly? Does anyone have experience using one in a modern 3800 V-6?

Where did you get the part number for the RobertShaw? They make thermostats for many applications. I'm sure they make one specifically for our 3800.

What happened in '86/'87? The end of the RWD 3.8 V6. The guys on turbobuicks.com are probably discussing the RWD 3.8. Not the Series I 3800, which was available in FWD form in the same era. (My mom's '86 Century 'vert had a 3800 with SPFI, pretty potent for a FWD car in it's day)

I found the RobertShaw part number at Summit Racing, which is specifically for 3800 V-6, but not listed for any after 1986. Using that number to Google search, I found the thread at TurboBuick.com, where they talk about modifying the lip to fit the GN motor.

It got pretty cold today (23ºF), so I decided to get one from AutoZone again. Their best unit was the Motorad Fail-Safe for $12.00, which is better than the Amazon price listed above. I think, based on how my current one is stuck open, I may have purchased the same one last time. Guy at the counter said they only sell 3 brands: Duralast, Motorad, and Valuecraft. He recommend against Valuecraft.

Planning to install tomorrow evening. I will verify if the old unit is a Fail-Safe or not.

Turns out the older t-stat unit was a Motorad, but not the Fail-Safe type. Surprisingly, the unit had not failed. Instead I found the rubber o-ring seal had broken away in two spots, allowing coolant to flow around the t-stat. The points of failure correspond to locations of assembly/weld points, where the valve support attaches to the flat disc:





Technically, the price of the repair was only $2.99 for the failed seal - I installed the new Fail-Safe t-stat since already I bought it. Will keep the other as back-up.

Aaron, where did you get the new stat-seal? I bought a couple from NAPA, and they were total garbage... They weighed about half as much as the old GM seal, and the edges looked like they had kids trying to cut circles out of rubber with scissors! So I just picked up a new stat from the dealer for $8 or $10, and the seal comes with it.

I'm not 100% sure, but I believe this is the OEM seal from GM. In my past t-stat swaps, I've never seen the need to change the seal until now. The new one is a Fel-Pro, sold through AutoZone as Duralast. Seems to fit just right.

That may well be - I don't have AutoZone out here... and this IS the first time I've been disappointed by Napa.

I was surprised that I needed a new seal! In search of my 2MPG loss I decided (especially for winter) to put a new 195 stat in place of my drilled 180. (Turns out that neither injector-cleaner nor a hotter, undrilled stat made a difference on my round-trip to Clear Lake at Christmas.)

However, when I was swapping out the 180 stat, I found that the rubber seal had 'dimples' in it from, of all things, aluminum corrosion - corrosion that was only where the seal was pressed between the manifold and and outlet...

In the last year, between stat, and hose, and radiator replacements, I've surely replaced all the coolant, but I guess I need to give it some of that extra Prestone additive mixture...

Would the SLP thermostat on 3800performance.com fit the Riviera? It's not on the listing, but I wanted to make sure it was interchangeable before making the purchase. Thanks

http://www.3800performance.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=SLP-TSTATS&Category_Code=CSFS&Product_Count=1

Yes, should fit, no problem. It's probably one of the ones listed above, so there is a mark-up on it.

Alright thanks. I try to stick true to brand, so my thermostat will match my SLP headers. Haha I know its silly, but to each their own I guess.

Yes, it is silly, but it's your money. SLP sources their t-stats from Motorad. You can pay $15 + shipping, our get the same thing at Autozone for $5-10 less. FYI, AutoZone calls them Duralast - same product.

Oh I misunderstood you.. well if its the same part then yeah ill definitely go to autozone instead.

I was idling at like 210ish with my 180 tstat a few days ago in traffic. Really thinking about trying a 160 tstat out just to see how it helps in the hot hot heat we are going to have this summer.

Probably need a tune to get the fans to turn on sooner too, huh.

OK, just read some. Never mind. I dont need a 160, I need a tune.

charlieRobinson wrote:

I was idling at like 210ish with my 180 tstat a few days ago in traffic. Really thinking about trying a 160 tstat out just to see how it helps in the hot hot heat we are going to have this summer.

Probably need a tune to get the fans to turn on sooner too, huh.

OK, just read some. Never mind. I dont need a 160, I need a tune.

Even with a 180 T-stat, you're still going to reach over 200*. Yes, if you want to reap the full "benefits" of a 180 stat, you need to have to fans kick on sooner...

Scott, as soon as I get my exhaust done, I will be paying you a visit!

charlieRobinson wrote:

Scott, as soon as I get my exhaust done, I will be paying you a visit!

That's what I'm afraid of

charlieRobinson wrote:

I was idling at like 210ish with my 180 tstat a few days ago in traffic. Really thinking about trying a 160 tstat out just to see how it helps in the hot hot heat we are going to have this summer.

Probably need a tune to get the fans to turn on sooner too, huh.

OK, just read some. Never mind. I dont need a 160, I need a tune.

My Eprom chip is tuned by Sinister to turn the fans on at 180 deg.I dont know about the series 2? you can install a sensor like this one to come on at any temp without the hassle of tuning your pcm.super easy to install and wont interfere with anything I think.1 fan runs for the AC,while the other fan runs the rad according to the FSM. Jegs also sells a single fan sensor too that you can program to run at 180deg



http://www.jegs.com/i/JEGS-Performance-Products/555/52126/10002/-1?parentProductId=1557724

Thanks, Robo, but I plan on just setting the fan variable in the PCM once it's tune time. ISNT THAT RIGHT, SCOTT, MA MAN!?