Is it safe to run with no thermostat? [Merged 8-7] No, no, no, no.

[GstRacer]

ya i was wondering if it's good or bad to run no thermostat i know it will run cold witch is good but is there a thing as too clod i also have a blitz 1.3 radiator cap

 

[60-1talon]

i just wanted to know if driving the car without the thermostat is safe

 

[project_tsi]

No. staring it up and running for a few minutes is ok, but
NEVER RUN AN ENGINE FOR A LONG TIME, OR DRIVE A CAR 1965 AND NEWER WITHOUT A THERMOSTAT. Period. Don't make me get Defiant on your ass about this one.

 

[urcnjoe]

I'm running without one now, but only until tomorrow when I have to pull my head and do a head gasket. Gonna be a fun weekend for me. Not a good idea if your car is operating properly. Why would you want to do this anyway???

 

[Defiant]

And please search this topic. Use "removed thermostat".

 

[Rice Over Wheat]

I just changed out my thermostat in effort to complete the overhaul of my cooling system and see lower temps here in hot ass Florida. I swapped out my 180*F thermostat and discovered it was stuck open, so my car was always being fed coolant. I guess this is why my car would take a good 10 minutes of driving to fully warm up to 185* or so. So I swapped in a brand new 180*F thermostat and a new o-ring. Just idling, my car warmed up in about 3 minutes to 190*...and kept rising! It hit 206* and I turned my SPAL fans on full in dsmlink. I hit 210*F just idling in my garage...at this point I decided to shut my car down because I'm going to put my stuck thermostat back in, at least I was running around 185-195 then.

This is with 40% coolant, 60% water, 2 bottles of water wetter, koyo rad, and powerful SPAL fans, and my manifold, o2, and dp DEI heat wrapped.

Since my thermostat has been stuck open and feeding coolant all the time for the last 6 months and my temps stay in a healthy 180 - 200 range this way, why not just pull the thermostat period and run without it? Again, this is Florida, not Maine. As long as I allow my car to warm up to operating temp before being hard on the throttle, I don't see the downside?

 

[fourreGsixty3]

It is normal for T-stat's to become fully open( they creep open, and don't just go from closed to open) 20* past what they open at (in our case 180*) I dont see your temp's as being abnormal since you are just sitting there in a garage...will driving the rush of air will help cool the rad. fluid. Its whe you start seeing temps in the 218*F+ tha you should worry. But to awnser your question I do't see any ill effect's other then wasting more gas at idle, and taking more time to warm to operating temp.

 

[Rice Over Wheat]

Good, that's what I figured. I just don't like every running hotter than 206* because of getting timing pulled plus I just like running cool, preferably in the 180s. Just hot enough for the ecu to adjust trims.

 

[fourreGsixty3]

I hear ya. If I lived in FL, I would opt for a cooler temp. then 200* just to be safe. Like I said before I don't see any problem with using the T-stat thats stuck open...its probably stuck open cause of the low gycol content( its used to lubricate the cooling system moving part's).

 

[jking29]

Running with no thermostat will cause problems also. You need some restriction to slow down the flow of coolant so that there is time for thermal transfer. It is the reason why Moroso sells restrictors for race cars. They are nothing more than a large thin washer with different size holes to adjust the flow rate. You can do the same thing by using a Dremel to trim the spring and poppet valve assembly from the stock thermostat.

 

[Rice Over Wheat]

Slowing the coolant flow for heat transfer, that makes sense. I'm going to have to decide on putting the stuck thermostat back in or drilling some holes in the "washer" thing. This new thermostat is definately not working out and makes my car overheat.

 

[prostreetdsmx1]

damn you all and your great advice. . I've been scowering the board for like 45 minutes looking for questions to answer and all the good ones are taken.

 

[GVR4592]

Slowing down the flow of coolant isn't going to drop temps by increasing heat transfer. If the coolant is in the block or head for a longer period of time it's going to get hotter not colder. This is why coolant temps increase a few degrees when you turn off your engine, the coolant is actually heatsoaking, just like an intercooler does. The only possible positive effect of slowing down the coolant flow, is eliminating water pump cavitation. If your water pump has an open impeller design it's more prone to cavitation, and that can cause temps to run high.

If your engine reaches operating temperature without a thermostat, I don't see any reason to run one during the summer. Just stay off the throttle when the engine is cold.

 

[RedTurboEclipse]

I have heard of cars in hot and humid places not run a thermostat. Mostly overseas. Mind you this isn't in a performance perspective.

Our family vehicle's thermostat was fugked and always overheating, instead of replacing it, we just removed it, now vehicle runs cool all the time. The temp gauge hardly ever goes to half mark. I havn't seen any problems with it. It does take long to warm up at night/cold.

 

[Rice Over Wheat]

Ok, sounds good. Pull the thermostat it is then. I knew I was in the neighborhood of thermostat theory. For a moment there I was getting whiplash from indecision!

I'll update on how it turns out.

 

[jking29]

Running a restrictor WILL help control heat better. The restrictor increases pressure inside the engine which helps steam pockets from forming around the cylinders and especially around the exhaust valves. It also slows flow through the radiator slightly, which increases thermal transfer. I used to run a small block chevy with 13:1 compression and was getting pre-ignition due to hot spots. I was running with no thermostat figuring the more flow the better. However, another racer friend suggested I try a restrictor. With no other changes my pre-ignition problems completely disappeared and I picked up a solid 1-1/2 tenths.

 

[bojanglesracing]

I though intercooler got heatsoaking from flowing air faster the it can cool.

 

[Rice Over Wheat]

Running a restrictor WILL help control heat better. The restrictor increases pressure inside the engine which helps steam pockets from forming around the cylinders and especially around the exhaust valves. It also slows flow through the radiator slightly, which increases thermal transfer. I used to run a small block chevy with 13:1 compression and was getting pre-ignition due to hot spots. I was running with no thermostat figuring the more flow the better. However, another racer friend suggested I try a restrictor. With no other changes my pre-ignition problems completely disappeared and I picked up a solid 1-1/2 tenths.

In that case I'm pretty surprised by that. What you described is exactly how water wetter works by decreasing the tension surface of water.

http://en.wikipedia.org/wiki/Surfactant

Also, I understand what you are talking about regarding flow, but I believe the radiator cap is what determines pressure.

I though intercooler got heatsoaking from flowing air faster the it can cool.

No, because an intercooler functions by displacing heat from the metal surface area to the surrounding air. The air must be moving to aid in carrying that excess heat away from the intercooler, so the faster the air flow through the fins the better. But at the same token, it can only cool the air within to ambient temperature. This is also why a radiator is more efficient with proper airflow.

 

[jking29]

In that case I'm pretty surprised by that. What you described is exactly how water wetter works by decreasing the tension surface of water.

http://en.wikipedia.org/wiki/Surfactant

Also, I understand what you are talking about regarding flow, but I believe the radiator cap is what determines pressure.

It does not increase pressure in the entire system. It increases pressure in the engine behind the restrictor. The added pressure within the block and head is what helps stop steam pockets from forming. And yes, water wetter does help to do the same thing, just using a different principle to do it.

 

[Rice Over Wheat]

Well I removed the thermostat and here are my results...

It took 15 minutes to warm up to 160*F while cruising. Mind you, this is with my fans on through dsmlink, so obviously leaving them off it would warm up faster. It's about 86*F outside. After this the car stayed between 174*F and 182*F, with my fans on.

Once I get my dakota digital fan controller wired up and set my fans to turn on at 170*F this is going to work extremely well. Warm up in about 5 minutes and constant temp between 180-190 in the summer.

I'm pretty happy without the thermostat and I'll see how it runs like this over the next few months.

 

[nightspeed87]

I just changed out my thermostat in effort to complete the overhaul of my cooling system and see lower temps here in hot ass Florida. I swapped out my 180*F thermostat and discovered it was stuck open, so my car was always being fed coolant. I guess this is why my car would take a good 10 minutes of driving to fully warm up to 185* or so. So I swapped in a brand new 180*F thermostat and a new o-ring. Just idling, my car warmed up in about 3 minutes to 190*...and kept rising! It hit 206* and I turned my SPAL fans on full in dsmlink. I hit 210*F just idling in my garage...at this point I decided to shut my car down because I'm going to put my stuck thermostat back in, at least I was running around 185-195 then.

This is with 40% coolant, 60% water, 2 bottles of water wetter, koyo rad, and powerful SPAL fans, and my manifold, o2, and dp DEI heat wrapped.

Since my thermostat has been stuck open and feeding coolant all the time for the last 6 months and my temps stay in a healthy 180 - 200 range this way, why not just pull the thermostat period and run without it? Again, this is Florida, not Maine. As long as I allow my car to warm up to operating temp before being hard on the throttle, I don't see the downside?

I live in Fl too, and I have a stock 190 thermo and dont over heat.
Why dont you leave your 180 thermostat in there as is, but wire your cooling fans to always be on soon as the ignition hits... At least thats what I did, and I dont have any fancy spal fans nor koyo radiator and when I hooked up my after market temp gauge it never got hotter than 205 at hot idle after hard driving,( and thats with a small n/t radiator)
so I disconnected it and didnt worry about it. Eventually I will get a koyo though, By the way I only have one fan, the a/c fan is history, but before I ditched a/c by wiring the cooling fan up this way the a/c fan automattically came on with it full blast at all times when ign was on. Helped a lot, and drove the car over a yr with it like that w/ no issues. I ran a wire from the blue and red wire ( dont mark my words on that ill have to check for sure if your really interested ) straight to the ign fuse in the interior fuse box, so when the keys on ign the fans are already on and it works good. Just make sure you have the car running or you can kill your battery fast by the drain the fans put on it.
Another thing that helped lower the temps when driving is cutting out the little planks on the top of the front bumper between the head lights ( they look like nostrils on both sides of the emblem ) This wont apply to your 2g but works for lowering temps with 1g eclipses and talons as more air is getting to the radi especially if you have a fmic.

 

[Rice Over Wheat]

I don't need to rewire my fans, dsmlink can set them always on. Also, like I said I have a fan controller about to go in to give me full degree control over my fans.

I also didn't have any cooling issues when I had my BT28 setup, stock rad, stock fans, the licp routed under the crossmember and nowhere near the downpipe. The evo3 and T28 are virtually the same size, just the evo3 flows a bit more. Upon installing my 50 trim, tial 38 recirced to o2 housing, and licp right next to my dp, I started having much higher temps.

Also, these aren't overheating problems per se, I just like to keep temps as close to 180* as possible where fuel trims are adjusted in the ecu, and as far below 206* where timing gets pulled. Running no thermostat seems give me just that range where I like it.

And btw, I have a 165A alternator, there are no charging issues.

 

[RedTurboEclipse]

So timing gets pulled above 206*? IF the only downfall is waiting a bit longer for the car to be fully warmed up, there really isn't any other problem removing the thermostat on ou cars?

 

[Rice Over Wheat]

Normal operating temps are 200 to 206F. It annoys me how the factory ecu settings are so conservative for initiating the fans on high, as well as how timing gets pulled so close to Mitsubishi's factory recommended operating temps. From dsmlink forums, here are important coolant temps:

Enter ECU Learn Mode :: 170F (180F for 2G)
Coolant Fan ON :: 200F
Pull 1 degree timing :: 206F
Pull 2 degree timing :: 224F
Enter Open Loop Mode :: 228F
Default Coolant CEL :: 235F
A/C Override :: 240F

It just takes so much time to go digging into the code to make sure the values are correct that I, for one, am reluctant to do it. For example, it has taken me 40 minutes to confirm all the following values...and I've got 82 other "updated threads" to wade through this morning. Granted, some of that time was spent coding up a little conversion tool so I didn't have to keep converting raw to "displayable" values from the code. But you get the idea.

The ECU will not update long term fuel trim values (called "learn mode" in the first post of this thread) under at least the following conditions:

2G: coolant < 179F, intake >= 133F, baro < 22.9 inHg, baro > 31.6 inHg
1G: coolant < 190F, intake >= 123F, baro < 22.9 inHg, baro > 31.6 inHg

The ECU will force open loop mode under a zillion different conditions, including the following.

2G: coolant < 51F, coolant > 228F
1G: coolant < 87F

Dave has already covered fan operation on 2Gs. I'll quote here again for completeness. At speeds less than about 45 mph with the A/C off, the radiator fan will be switched on low at 210 and off at 203. Under all conditions the radiator and A/C fans will be switched on high together at 224 and off at 217.

Fan operation on 1Gs, of course, is not ECU controlled.

The 2G code includes a manual (as opposed to table based) reduction in ignition advance that does not appear to be present in 1G code. This pulls a total of one degree of timing at 206F or a total of two degrees at 224F (they are not cummulative).

Intake temperature will also cause a reduction in ignition advance. The tables are laid out like so, with interpolation occuring between the points.

2G intake air temp ignition advance adjustment:

185F = -3°
132F = -2°
100F = -1°
73F = 0
48F = 0
20F = -1°
-23F = -2°

1G intake air temp ignition advance adjustment:

185F = -3°
132F = -1°
100F = 0
73F = 0
48F = 0
20F = -1°
-23F = -2°

Whew. OK, hopefully that's enough for now.

Thomas Dorris

 

[Defiant]

A thermostat is not for cooling an engine. The radiator cools the coolant. A thermostat warms the engine, and keeps it warm. It also restricts flow, not only to prevent impeller blade cavitation, but also to keep turbulence from high-flow to allow steam pockets to form in such areas as the exhaust guides.
As you've been shown, running without a restriction is bad. And you've shown yourself what a lack of thermostat does- it makes an engine take forever to warm up, and you'd find in driving that it won't hold its intended operating temperature.

Restrictors in place of thermostats is only one of the many race mods that just don't translate to the street. You can't run hard enough long enough, consistently enough to make it work.

 

[Rice Over Wheat]

What is water pump cavitation? The good thing regarding regulating operating temps is that my digital fan controller will handle that. What I saw while driving was with fans always on. I'm going to set my fans to come on at 190 and off at 180.