17 replies to this topic

[bmarshall1]

In a '99, is it best to run with or without a thermostat; if yes, then what temp range?  Please support your opinion so I can learn.

 

I have heard varying opinions and reasons but it's been awhile.  If I recall I believe I have one in my '99 (195 degrees?) but an engine builder recently stated he does not run them in 99's  (but does in the 2001+ due to the vvt.

[FTodaro]

The biggest con of running a stat is if it fails it can kill the motor. Now that they changed the rule back so you put tape in front of the intake screen to the rad I just run tape to get the desired temp. It's a little more work but you can get the result your looking for.

[Michael Novak]

Run a thermostat.  Remove the flex pin and drill its opening to 1/8 or so. Automakers have been putting thermostats in for ever and they rarely fail.  180 degree

[ChrisA]

Run a thermostat.  Remove the flex pin and drill its opening to 1/8 or so. Automakers have been putting thermostats in for ever and they rarely fail.  180 degree

 

 

This is what I do, but may have drilled out slightly larger. I tried 1/4, but it was too large a hole. I still need to use some tape on cold sessions or it takes too long to get up to temp. I use the NAPA THM-535080 T-stat. It's a good piece. 

[Rick Worth]

#THM142 is a NAPA 180* thermostat that is more of a universal one with no drilling required. Had it in our Spec Miata for 3 years with no issues. 

[tylerbrown]

Run a thermostat.  Remove the flex pin and drill its opening to 1/8 or so. Automakers have been putting thermostats in for ever and they rarely fail.  180 degree

 

Had one fail getting stuck closed and if not for my aim gauge flashing at me, that motor would have been a goner! In the past when I have asked, half the people say I should, and half say do not. 

[Steve Scheifler]

For me it depends largely on the weather forecast. In the hot midwest summer when even mornings are warm I like to run just a gutted t-stat “plate”. But if it will be cool enough that we can’t achieve 180f or it takes too long to get there, then we run a 180 with either the built-in hole & rattler or a drilled equivalent. It may be a sign of our own weekness, but as a purely DIY “team” we are busy enough between sessions without adding the issue of taping the radiator or not. We’ve tried it, but I’ve lost more seat time and risked more damage from forgetting to put it on or take it off than from the unlikely failure of a quality thermostat.

[bmarshall1]

Thanks for the replies, I have been finding all sorts of answers.  They run from - you need the extra flow, slow the water down so it has time to cool, you don't want cavitation, only remove the t-stat guts to build pressure in the head and force the water out the back, the head is already restricted so the water will already go out the back, above 195 the car will pull timing etc...  Since I don't have a 'real' temp guage (just factory)( I know, it is basically a on/off hi/low type of guage) and would not be able to tape the proper amount to get the proper temp, I'll leave well enough alone until I get a digital guage.

[38bfast]

It depends on what radiator is in the car and the condition of the radiator. On cars with a new good cooling radiator we run a stat. On cars with cheap o or beat up rads we run without the stat. Tape works but its a pain and doesn't always work out well in a draft. 160 or 180 stat. On a 1.6 we try and keep them as cool as possible. 

[bmarshall1]

Thanks Ralph, it's a Davis radiator that came with the car, age unknown but inside is pretty clean.

[Mark]

No to tape. Too easy to forget that its there. Grab a bunch of stats (Rock Auto?) and look at them. There is a surprising amount of variance in the bleed holes, opening diameter, and depth/gap when open between the various brands. It makes a difference. Pick your poison . The temperature rating on a thermostat dictates minimum 'warm' engine temp. The thermostat does not control ultimate motor temperature. For us a 160 was too cold, A 180 kept the motor in the right map on the cool mornings. A healthy cooling system takes care of protecting the engine on the warmer days and hot afternoons. We do keep a gutted thermostat around for the 'when all else fails' moment but haven't needed to go there yet and it gets pretty darn toasty in SoCal. 

[bmarshall1]

Run a thermostat.  Remove the flex pin and drill its opening to 1/8 or so. Automakers have been putting thermostats in for ever and they rarely fail.  180 degree

While I agree they rarely fail, it's ironic that when I bought the car and went through the motor, the thermostat was broken into several pieces.

 

When you say 'flex pin', are you talking about the 'rattle pin'?  What is the purpose of drilling the hole larger; extra cooling?

[Steve Scheifler]

It’s primarily an air bleed. Not sure you can get meaningful flow of coolant through it.

[Dave D.]

While it is known that certain engines/systems like to run warm for power, does anyone really know at what temp things happen? Meaning at Xdeg, you switch out of warmup map, at Y temp timing gets pulled so much for each degree over.......etc

[gerglmuff2]

minnesota, 1.6L racer ... no thermostat. 

though if im going to a cold track day in april or october, i sometimes will put one in. its about a 15 minute thing, i just keep extra gaskets and a thermostat in the truck, its two bolts. 

[Steve Scheifler]

While it is known that certain engines/systems like to run warm for power, does anyone really know at what temp things happen? Meaning at Xdeg, you switch out of warmup map, at Y temp timing gets pulled so much for each degree over.......etc

Depends on where you pick up the temp. Best to experiment on a dyno, but that requires close monitoring/control of IATs or you’ll chase your ass in circles.

[SaulSpeedwell]

Run a thermostat.  Remove the flex pin and drill its opening to 1/8 or so. Automakers have been putting thermostats in for ever and they rarely fail.  180 degree

Agree with this 100% but we are Northerners, and you are fast enough (and I was once fast enough) to be in clean air much of the time.  The "gutted thermostat" was the coldest running thing I tested, and I tested engine cooling (air and water) on 1.6 and NB as much as I could, including bombing down country roads at 100mph in the Wifemobile mint low-mile Green/Tan '99 with OBD-2 logging and thermocouples and a Magnehelic duct taped to the windshield testing 8 combinations of stock inner fender liners and various taped up grill openings.

If you can stay below timing retard (204-207F as read by the ECU depending on year, IIRC, but botched Autometer installs could be 20 degrees off), I would run a thermostat every time as Novak says.  But if you are running hotter than 200F on a given weekend, rip off the "chicken wire", seal up all the air gaps around the radiator, run a "gutted" thermostat … and then re-evaluate your entire cooling system after you have retubbed the car because of a bad pass for 12th.  





 

[Tom Hampton]

It was 11th, damn it! And it was a good pass.