Wheelman

Could somebody give me the benefits of doing this?? Its beginning to get hotter down here in Houston and I want to get my temps down a bit for the warmer season. Car just doesn't pull as good when its running at 225...

jackdaroofer

:cheers: Drilling a small hole in the deck of the thermostat allows a small amount of coolant (large hole[s}, large amounts) to pass through system with thermo closed. Generally this is done as a cure for air getting trapped in the system.

The holes can reduce the temps, if they are hovering around or slightly above the thermo preset. Say in a 180 thermo, hole(s) can the effect to say 175 deg

But at 225 degree, thermo is wide open and holes will have on impact. I would suggest switching to a 180, drill one 13/16 ths hole and try that. You might also want to pull the radiator and clean it and the area in front of it and flush your system

:seeya

:steering:

CFI-EFI

That looks like MY sort of typo. I think Jack means, one, only, three sixteenths inch hole. I agree. Too many or too large holes only serve to bypass the stat, increasing warm up time.

RACE ON!!!

dwestsr

I drilled 4 1/16 holes equally spaced around the flange of the thermostat. With a 180 Tstat, My temps in winter are 175. In summer, it doesn't matter because when the tstat opens , It no longer controls upper temp. Best thing about the holes is the purging of air in the cooling system. In summer , the tstat is not the limiting factor in cooling. :cheers:

jackdaroofer

:smash: :rolleyes: :bb

Sam Lam

I drill qty 2 holes 1/16 inch in diameter in the flange of the thermostat. I cannot detect if these affect the function of the t'stat. It sure does help purge air from the system and the "packing of coolant" is not required.

84whitevette

Do you guys mean it helps to purge air when servicing the cooling system? Or just with daily use? I'm curious.

Sam Lam

I use the "two holes" in the thermostat only when servicing the coolant system. Otherwise, I cannot detect any change in the everyday use of the system. When you fill up the coolant system, the holes allow air to escape and the system will fill with water....not air!
SAM

Topless87

On your 89, like my 87 the only way to get temps down in the summer is to get the fan to turn on sooner. Either reprogram the ECM or get a bypass. Ecklers has them for about $40 i think. This gets the main fan going about 20 degrees sooner. Oh, and a 180 t-stat. I wouldn't go lower than that.

I had one $%)(@W of a time getting my coolant level light to stay off, after a year of thinking I had a leak somewhere, I drilled 2 small holes in my t-stat. within a few miles and topping off the overflow tank, never had the coolant level light come on again.

86PACER

I drilled 4 holes in mine. This reduced my temperature spikes and kept my temperatures more stable. I run a TPIS 170degree thermostat, low temp fan switch, 70/30 coolant/water mixture. My temps stay betwen 180 and 200 degrees in traffic. :D

BIG JIM 54

Well,

I agree with the 4, 1/16" holes drilled in the thermo body (the part that doesn't move). But switching to a 180F thermo from a 190F, doesn't make any difference at all. The shop who built my engine installed a 160F and I installed a 200F fan switch. That will make a difference.

Since then though, I've removed the thermostat completely. But in South CA, it rarely drips into the 40's even during the peak of winter. You may not want to remove your thermo if you live in colder climates. I can't imagine putting my 'vette in storage for months on end and not drive it like a friend of mine living in Illinios does. He may not have quite enough sense to move to a better climate but at least he's got enough gray matter to install a heated garage. Haha.

BIG JIM

LT4BUD

I tried this last year on a 160 stat. Based on my experience I would say don't do it.

First it really delays getting to operating temperature, especially if it is cool outside, less than about 70 degrees.

Second in temps below about 60 degrees my car never got to operating temperature. The result of this was slightly blackened oil for the first time ever, I assume from the car running too rich.

Finally, I really saw no significant improvement in max temperatures during hot weather!!

If you are running too hot look at other solutions.

:seeya


[Modified by LT4BUD, 7:53 AM 3/22/2004]

Swede

Hello friends !!
I have drilled 2 holes in my std thermostat, they are 4,5mm or about 0,177" and my engine is working around 170-180 deg/F all the time, no matter how hard Im driving. The backside is that it will take a lot longer time to warm her up, almoust twice the time.
Regards Magnus. :seeya

Chatman

I personally don't have a problem with the Corvette, but I use the small drilled hole for safety sake in all cars. All that is needed is one hole on the top side and any small size is fine (1/16th=1/8th). It serves the purpose of preventing an air lock when refilling the system. But even with one small hole, you will notice a minor delay in the engine reaching operating temperature. However, preventing an air pocket is worth it.

FYI. There is nothing new here. The thermostats for my old Jaguar XJ12 (Wexstat) came with holes and a directional "ball" to seal the hole. Also, my daughter's LeBaron has a special problem with air pockets and the small hole approach makes a huge difference there.

Basically, there is no reason to not add one small hole to let air through and a small stream of coolant flowing through is no big deal to a system with temperature controlled fans.

Steve

Mike_88Z51

I had a similar problem with my 88. Always ran about 225 ~ 235+ on hot days. As already mentioned, if you are getting above 200 degrees the 160 thermostat is no better than the 180 for cooling and adversely affects warm up to proper operating temp for closed loop operation.

If you don't know thw age of your tstat, it might help some to replace it with a new 180. The old one may not be opening completely. I also use the 1/8 inch hole in the tstat base to aid in venting air from the back side of the system. Works great.

Set aside a weekend morning to drain and pull the radiator. Your first time it will take about 1-1/2 hours to pull it from an 89 if like me you are really slow and stop to clean. After that it shouldn't take more that 30 minutes to pull the rad. Not that hard at all. Tools needed are a couple of screwdrivers and a 1/4 inch rachet, some extentions, and metric sockets. Use some Simple Green or Dawn in solution and with a SOFT brush, CAREFULLY scrub the fins on both sides with the solution. Repeat scrub CAREFULLY, the fins are fragile. Rinse completely with a garden hose. Using a small flat bladed tool or screwdriver I straightened every possible fin that I could (this took the most time). Reinstall radiator and add new coolant mixture. I spent 4-1/2 hours total on mine getting it completely clean and every fin straight. I immediatly saw my max temp drop from 235+ to 220 in traffic on 100 degree days. Fifteen degrees may not seem like much, but 220 is the max ever under the worst conditions. Generally it stayed in the 180~200 range day or night.

I then replaced my secondary fan switch (factory is on at 225) with one from Mid America which turns the seconday fan on at 205 and off at 195. Cost is about $20 and it is a simple unscrew the old/screw in the new task. The highest temp I have ever seen since the cleaning and switch change is 217 sitting in line at a drive thru on a really hot day. Problem completely solved.

lite blue

The TPIS hints book recommends drilling the holes because they also plug the small bypass hole in the water pump, on the flange where it meets the block. This supposedly forces all the water through the radiator. I did both of these last time I put on a new water pump....seems to work well. :thumbs:

Mr6spd

You win the prize for the correct answer to the question!

Plug the bypass holes in either the pump or the block (which requires holes in the t-stat for proper reciculation). This will result in a higher coolant flow rate through the block and engine, and result in easily measurable max temperature decreases. BTW, the old tale of slower coolant circulation resulting in better cooling is pure bs.

BIG JIM 54

Yeah, I agree totally.

I don't even run a thermo and if I ever hit 200F, it's because I've waited in the drive-thru line a little longer than normal. I run 165F at night on the freeway. Colder means more HP.

The purpose of drilling the holes in the thermo is not to reduce running temps in itself but to prevent air being trapped behind the thermo and an air bubble in the cooling system will keep the "add coolant" light on (if so equipped) when the radiator and coolant recovery bottle is seemly full. And THAT will make the temps climb big time. But that's only if you don't bleed the system.

BIG JIM

89Corvette6spdFX3

Don't forget to do the Throttle body bypass! That will help a little.