I have the Hypertech fan switch that turns the fans on at 200 and off at 185 for my 1987 coupe. I have not installed it yet. I was wondering if it was necessary to change out the thermostat to a lower value (Ithink the stocker is 195) to use this effectively, or if I can leave the stock one in there. Any recommendations? If I really need a new stat- which one do you recommend and where would you suggest I buy it? I am going to use the tech tip on controlling both fans with this switch so the front one doesn't have to work alone to cool this beast. Thanks for any insights!
Brad

 

change your thermostat to a 180.if you have a local speed shop they should have a nice balanced flow one for under $10...stay away from the cheapos at the local parts store.

 

In the summer and under 35 mph, your coolant will go to 200-220F, BUT when you get underway it will not fall to 185 and your Hypertech will keep both fans running for the rest of your driving. This will shorten the life of your fans and it will not contribute to engine cooling above 35 mph. A 180 stat in the summer will be wide open after the engine coolant goes above 180 because your 87 radiator is sized to maintain 195 when you are above 35 mph and ambient is not above 90F (in my experience with my 87). A 180 stat can only control the coolant temp to 180 if the radiator has the heat ridding capacity and your 87's radiator does not.

 

jfb, your knowledge is usually excellent, but the above post I must disagree with.

A thermostat is not wide open at the stated temp of the thernmostat. A 180 thermostat should remain closed and not even start to open until the coolant temp reaches 180F (plus or minus a couple of degrees due to manufacturing tolerances). A thermostat should be wide open at its stated temp plus 20F. So a 180 thermo should be wide open at 180F + 20F or 200F (plus or minus a couple of degrees). For reference see section 6B in your Helms Factory Shop Manual where it describes how to test for a properly working thermostat. You can also talk to the STANT technical people as I have. (OEM supplier for Corvette thermostats.)

According to the official 84~91 GM Dealer Parts Guide, the 86-89 C4s all used the same part number for the radiator #52453612. That being the case, I can tell you from actual experience with my 88, which should have the same stock radiator as the 87s, that if your 87 system is clean and workng correctly, a 180 thermo should not cause the fans to be on all the time at 35mph. I usually see 180~185 at 35~50 mph on days with ambient temps 90F and below. I've had a MAD aux fan switch that turns on my aux fan at 205 and off at 195 in my 88 for 5+ years and the aux fan is still not worn out. Other than when the A/C fan switch has kicked on the main fan, my main fan has ony come on one time in the past 6 years due to heat causing the coolant temp to reach 226F (GM Factory main fan start temp). The 86~89 radiator in conjunction with a 180 thermo can easily keep you near 180F if clean, unobstructed internally and externally, and the antifreeze/water coolant mix is correct.

 

88Z51, You need to take a reading comprehension course. I said, "....when the coolant goes above 180..."
Also, when the engine temp gets to 200 and his fans come on, the engine temp will have to go to 185 for the fans to go off and even above 35 mph, in the summer time the coolant temp will not go below 185 with stock radiator and water pump!!! So once the fans come on, they will stay on until the engine is shut off and it cools to below 185 F.
I'm not going to search the posts, but many CF members with 180 stats have posted that their coolant temps in summer temps stays well above 180 F!!!

 

Thanks for the replies and info. Hmmm.. I may just rethink this. Anyone else have any comments?

 

i have to say that my 85 with stock waterpump and radiator does stay below 180.my fans both kick on at 195 and off at 180 and i have no trouble staying in that temp range.you could try the 180 stat and see how your car handles it,it is not hard to change it and you can always put the 195 back.you only have to drain down the cooling system below the level of the stat,i just used a siphon to drain enough out.stats are cheap and your labor is free,its worth a shot.i can sit in traffic and see the fans kick on and off so i know my system handles it fine,i never hit 220 anymore any time.try it and see is just my opinion.

 

jfb, What you actually posted was "A 180 stat in the summer will be wide open after the engine coolant goes above 180..." I didn't get the highest grade in my college thermodynamics classes, but I do know that a coolant temp of 185 is above 180 and unless it is defective, his 180 thermostat WILL NOT be wide open at that temp. A coolant temp of 190 or 195 is above 180 and unless it is defective, the 180 thermostst WILL NOT be wide open. Perhaps you meant in the 200+ range above 180, but that is not what you posted.

What you say might be true. If his system isn't working at top efficiency you are probably right. However, if it is clean inside and out and working properly it should be able to get temps below 185 on many a summer day. Depends on how hot the day is. In general, vettenut85 and I both have personal experience that is different from yours.

I am sure that you are quite right about this. That doesn't mean that all of their systems are clean inside and out and operating optimally.

I have a stock 88 with a clean, properly working, all stock cooling system, except as already noted for the aux fan switch which turns on the aux fan at 205 and off at 195, and the slightly higher ratio of water to antifreeze (60/40 mix of Prestone green). At sustained speeds above 35mph in the summer I usually see 182 plus or minus 3 degrees with both fans off. Before I thoroughly cleaned my radiator and replaced my worn out radiator cap, I would have agreed with your viewpoint. Now I know different. The C4 cooling system is pretty efficient when working at its optimum . I don't claim to see 182~185 at 35mph on a 105 degree summer day, but on a 90 degree day at 35mph my 88 which uses the same radiator and cooling system components as he 87, is usually under 185. Your mileage may vary.

 

1987C4, I have to say that if your cooling system isn't in good shape you should listen to jfb on this. If you use a Hypertech 200/185 fan switch and you haven't got a clean well operating cooling system, you will probably see the fans on way too much with a stock 195 or even a 180 thermostat. The key is to get the cooling system in optimal condition. Pull and clean the radiator inside and out. Really wash the fins clean on the outside and use a new pressure cap.

For a street car, my personal opinion is that any switch that keeps the fans on until you get below 185 is doing too much fan work. I'd consider one that stops at 190 or 195.

 

87 C4, I'm using a temp switch that both my fans comes on at 200 and off at 185, a 180 degree thermo, clean area between radiator and condensor-for the past 2 years, vette runs up to 202 in traffic with ambient temps around 85-that's hot in Seattle, on the highway I stay around 185-I'm happy and my oil temps are pretty much in line with coolant temps.