Thermostats without bypass valves

[HenryJ]

Split topic-HJ

Does that Stant thermostat have a bypass valve?

Does it look like this? If it lacks the bypass valve, I'd pass. You will be bypassing coolant that should be benefiting the cooling rather than continuing to bypass when the thermostat opens.

[crew cab sonoma]

Does that Stant thermostat have a bypass valve?

Does it look like this? If it lacks the bypass valve, I'd pass. You will be bypassing coolant that should be benefiting the cooling rather than continuing to bypass when the thermostat opens.

HJ, give the thermostats W/O a bypass a chance.
last summer, i had quite a few days at or very near 100 deg. temps,
a partially clogged OEM radiator, and a 170 stat without the bypass valve on it.
and cooling fans operating at low speed only.
truck managed to maintain 180-190 deg.
operating temps, even after extended driving in stop-n-go traffic....

[LonestarZ]

Keep in mind I live in Texas... so it gets hot, some would say damn hot! I had a 180* stant on my '97 ZR2 and it worked great. Of course the PCM has changed and I am looking at running a extra capacity radiator.. so there are some different factors.. I don't know. I guess I will find out when I get all this installed.

Right now I am waiting on some additional shocks. While I bought some replacements for the front my right rear decided it was done and has started leaking. So hopefully I will get those changed out this week.

Thanks for the discussion guys.

[HenryJ]

... If it lacks the bypass valve, I'd pass. You will be bypassing coolant that should be benefiting the cooling rather than continuing to bypass when the thermostat opens.

...give the thermostats W/O a bypass a chance. last summer, i had quite a few days at or very near 100 deg. temps,
a partially clogged OEM radiator, and a 170 stat without the bypass valve on it.
and cooling fans operating at low speed only.
truck managed to maintain 180-190 deg.
operating temps, even after extended driving in stop-n-go traffic....

Wait until you see extended periods of temp in excess of 100.

I am not even going to try going without. It just doesn't make sense to have the water pump bypassing coolant. Reducing the efficiency of the waterpump is counter productive.

Will it work without? Heck yes. The big block Chevy has a hose to bypass coolant to the manifold, as do some Fords and Dodges. Can they stay cool? Sure.
Want to keep them cooler when you hotrod one? Yep. Add a bypass block or restrictor
My HenryJ runs a Flowcooler aluminum pump with a blocked bypass.

If it made sense to eliminate the bypass valve, I would. Everything I have done to my truck has been to enhance the cooling efficiency. Why would I take a short cut and save $10 to run a cheap stat without a bypass valve?
It just seems like cutting corners. The correct style stat is available. Why not use it?
Heck I spent $100 to upgrade the radiator and more than that to make other changes.

Sorry to hop up on a soap box, but it is just like spending $50,000 to build a nice streetrod and then put steel wheels and hubcaps on it.

Now you could tap and install a restrictor or plug in the bypass passage. This could be a problem for this engine though. cavitation was a problem for this engine. It is unclear if it is the rpm, reverse rotation, Dexcool or all of the above that contribute to the problem, but the problem does exist. The bypass allows the flow to continue while the thermostat is closed. This reduces the likelihood of cavitation and pump damage. So it does need to be there and still working to enhance the lifespan of the waterpump. Cooling might benefit from plugging it, but at the expense of the pumps life.

Now, you could argue the fact that the coolant needs to spend enough time in the radiator to transfer the heat. A faster flow can inhibit this transaction. That may be true, however the stat offers the restriction needed to offer the time needed. The higher flow is beneficial and even more important when the radiator contains a large pool of coolant, and the efficiency of the radiator is good enough to handle increased flows. The stock radiator may not be efficient enough, or contain a large enough reservoir to take advantage of a good flow. Adding a larger radiator this may be of more importance.

The nice thing about the stat with the bypass valve is that as the stat opens the bypass is closed. It is variable. A nice idea.

The valve sure seems like the best of both worlds. I wish I did have one on the HenryJ. It might free up a few horses before the stat opens.

I guess if it works for you, great. If the time comes that you need that little extra, think about spending the money on a stat with a valve.

[LonestarZ]

Your going to love this.. all this discussion is moot. I decided to look up the part number on the Tstat that I originally bought for my 2000 ZR2 to see if it is compatible. Turns out that Tstat is only compatible with a S10 from 20 years ago!!! WTF!

The only performance Tstat that Stant offers is a 190* (Part # 45119) which I still will probably pick up. At least with the Tstat running at this temp it should not trip any SES lights.

[crew cab sonoma]

had the "right" thermostat with the bypass valve on it...
i cut it off....

the end result is that it works great without it
even one 98 deg. day, i decided drive the Ext. Cab up a local mountain. spent about 8-9 minutes to get to the top, still didnt get over 195 deg.
this was with elec. cooling fans running at low speed, and with a stock radiator that was probably at least 1/3 clogged, possibly more...

with my new bigger radiatoractually, i`d love to try it in even hotter weather... i fully expect it maintain 170 this summer...

i know many reputatble big name guys claim increased cooling "efficiency" by restricting, or even blocking bypass circulation. but if you open up bypass flow, and still dont run hotter, where is the increased "efficiency" at???

i`ve seen plenty of first hand experience that indicates incresed bypass recirculation (at least up to a point), does NOT hinder cooling system "efficiency" , which would be indicated by an increse in operating temperature...

to the contrary, increased bypass circulation can often have several advantages.
more even block-to-head temperatures.

possible reductions in "hot spots" in the cyl. heads.... sometimes EVEN if the overall operating temp is slightly higher...

and potential reductions in waterpump drag, from reduced pressure differential across the pump...

reduced potential for pump "cavitation", and even reduced chances for belt slippage in some cases...

as far as i`m concerned, increased cooling "efficiency" isnt quite as simple as it first seems to be....

naturally, excessive recirculation can lead to overheating, but many would be surprised just how much it really takes to cause this...

i dont really think your analagy about $50,000 hotrods using hubcaps necessarily applies to this.... even on a hotrod, why spend more money than you have to, only to get the same result???

not using a bypass style thermostat is about more than just saving a few bucks. at least to me it is...

i have a spare 4.3 intake manifold, that i`ve been porting on. and
based on 3 summers of driving without a bypass valve on two different trucks, i am seriously considering cutting the bypass "pad" out of bottom of the thermostat area, and welding on a threaded fitting on the front of the manifold, so i can experiment with even larger bypass flow...

i have done it with other vehicles in the past, with good results...
in the end, "to each, his own", i guess. just think about it, is all i challenge you to do....

[HenryJ]

... if you open up bypass flow, and still dont run hotter, where is the increased "efficiency" at???

i`ve seen plenty of first hand experience that indicates incresed bypass recirculation (at least up to a point), does NOT hinder cooling system "efficiency" , which would be indicated by an increse in operating temperature...

That is not really a persuasive argument. Time to operating temperature needs to be calculated. A fast warm-up is as essential as maintaining the temperature. It works because , "I don't get hot", is not a good argument. Mine doesn't get hot either and I have the valve.

...increased bypass circulation can often have several advantages.
more even block-to-head temperatures.

possible reductions in "hot spots" in the cyl. heads.... sometimes EVEN if the overall operating temp is slightly higher...

and potential reductions in waterpump drag, from reduced pressure differential across the pump...

reduced potential for pump "cavitation", and even reduced chances for belt slippage in some cases...

No argument here. I have a functioning bypass. As the thermostat opens the flow is routed to the radiator. When the thermostat is fully open the bypass is closed and all the water pumps flow goes to the radiator to exchange the heat.

...excessive recirculation can lead to overheating, but many would be surprised just how much it really takes to cause this...

Exactly! Why move closer to that point. I want to go the other direction.

...i dont really think your analagy about $50,000 hotrods using hubcaps necessarily applies to this.... even on a hotrod, why spend more money than you have to, only to get the same result???

There are places to save money and things that you should not try to save a dime. My only point here is that there are better ways to save. I am not saying that the Hotrod needs custom built billet wheels, but for heavens sake don't try to save a buck. Put some nice wheels on it. Relating this to the current discussion, I just don't see saving $10 to install a thermostat that is not designed for the application and doing so COULD adversely affect the function of the cooling system.

...not using a bypass style thermostat is about more than just saving a few bucks. at least to me it is...

Sorry I still don't see any benefits. The only time there is a difference is when the thermostat is fully open and that is when you need the maximum heat transfer from the radiator. Why would you want to recirculate the coolant by eliminating the bypass valve?

i have a spare 4.3 intake manifold, that i`ve been porting on. and
based on 3 summers of driving without a bypass valve on two different trucks, i am seriously considering cutting the bypass "pad" out of bottom of the thermostat area, and welding on a threaded fitting on the front of the manifold, so i can experiment with even larger bypass flow...

That would be interesting. Add something where you can easily adjust the flow. I still think the valve on the thermostat is doing all that for you and why would you want to do it manually?

just think about it, is all i challenge you to do....

I have more than I really want to. Thank you. This is a good discussion and really is worthwhile.

I am sincere when I say thank you. There is meant to be no sarcasm. This is a good topic. I am glad it works for you, but I think this widget doesn't need fixing. I do wish there were more choices for the temperature range on the thermostat, but the three that are available will have to do for now.

[crew cab sonoma]

That is not really a persuasive argument. Time to operating temperature needs to be calculated. A fast warm-up is as essential as maintaining the temperature. It works because , "I don't get hot", is not a good argument. Mine doesn't get hot either and I have the valve.

why would time to operating temp change? during sub-operating temps, the bypass is open, either way. the coolant is recirculated internally through the engine. warmup time is unchanged.

now if the thermostat had "bypass" holes drilled into the thermostat housing, that would slow warmup time. but thats not what i`m talking about here.... i know thats what some do when they block the internal bypass flow, drill holes in the themostat to compensate for lost recirc. flow, but i am OPENING up rcirculation flow, not closing it off...

No argument here. I have a functioning bypass. As the thermostat opens the flow is routed to the radiator. When the thermostat is fully open the bypass is closed and all the water pumps flow goes to the radiator to exchange the heat.

well, not all of it. some still bypasses through the heater core. and the the thermostat will "close off" any ammount of flow needed to maintain operating temp., which can lead to some restriction of flow to the radiator. what i`m doing, is allow this flow to recrculate through the engine, instead of "deadheading" behind the thermostat...

Exactly! Why move closer to that point. I want to go the other direction.

i`m not so sure i really have moved closer to that point. at least to a significant degree... i still think the pros of my mod outweigh the cons...
my slightly above normal operating temps on the Ext. Cab were due to a plugged radiator, not not the opened bypass. the Crew had seen similar summer temps and conditions with the opened bypass, and managed to maintain 170 deg. without problems...
with the new radiator in the Ext. Cab, i forsee no problems with it this summer...

Sorry I still don't see any benefits. The only time there is a difference is when the thermostat is fully open and that is when you need the maximum heat transfer from the radiator. Why would you want to recirculate the coolant by eliminating the bypass valve?

There are places to save money and things that you should not try to save a dime. My only point here is that there are better ways to save. I am not saying that the Hotrod needs custom built billet wheels, but for heavens sake don't try to save a buck. Put some nice wheels on it. Relating this to the current discussion, I just don't see saving $10 to install a thermostat that is not designed for the application and doing so COULD adversely affect the function of the cooling system.

agreed, but it hasnt adversely affected mine. and as i said there may even be benefits. after all, modding/hotrodding cars and trucks is all about altering stock specifications, and often using/installing parts that were never designed or recomended for our vehicles, that COULD adversely affect them.
chances are, your truck has quite a few more of them than mine does....

it apparent to me that the waterpump has more than enough reserve flow capacity to deliver all the flow the radiator needs to adequately cool the engine, plus the extra recirculation. if additional flow to the radiator is needed for cooling, the thermostat is obviously opening more to direct additional coolant to the radiator...

I am sincere when I say thank you. There is meant to be no sarcasm. This is a good topic. I am glad it works for you, but I think this widget doesn't need fixing. I do wish there were more choices for the temperature range on the thermostat, but the three that are available will have to do for now.

indeed. i thank you as well. this is a good debate, and hopefully informative to some here.
it is a shame the 170 isnt available from Autozone anymore.
but as far as i`m concerned at least, there is an ample variety of thermostats, in any temp. wanted, readily and inexpensivley available at any local parts store...

[quickbiker]

Which of these are the best?

One
Two
Three

[HenryJ]

Which of these are the best?

One
Two
Three

There is only one choice.

#1 does not show a bypass valve, and therefore is not an option in my book. #2 is for the four cylinder, so I have doubts as to whether it would work.

#3 JET-10171 is the best choice and the one that I am using.

[killian96ss]

Which of these are the best?

One
Two
Three

I have to agree with Brule on this one, #3 is the best choice and the only one I would recommend.

Steve

[quickbiker]

Thanks. Yea, I just realized #2 was for the L4. And what's up with #1? It sure does look nice. lol

[HenryJ]

... And what's up with #1?

Fits full and mid size trucks only.

Wrong application again , I guess.

[quickbiker]

Doesn't look like #1 is wrong app, just no bypass valve. I just wonder what makes it so pricey.

[HenryJ]

Doesn't look like #1 is wrong app...

?? Fullsize with the 4.3L don't have a bypass , I guess.
Not the correct application for our trucks is what I should have said? Ours is neither full or midsize. The S-series is listed as compact or small sized.

[quickbiker]

It says full and mid size. Dunno.

[killian96ss]

Doesn't look like #1 is wrong app, just no bypass valve. I just wonder what makes it so pricey.

Don't rely on that picture to be accurate!

I ordered a new t-stat from Summit 3 separate times for my S10 Blazer before I finally got the right one.

Summit uses that same picture for several of Hypertech's t-stats. All 3 t-stats they sent to me were completely different from one another.

The only good thing that came out of this confusion was that they let me keep the other 2 t-stats for free. I believe I have Hypertech part #'s 1018 and 1020 if anyone needs one for whatever application.

Steve

[quickbiker]

Gee, yea. I don't find that too hard to believe. They are a bit goofy at times. But I'll hand it to there responses, they want the customer to be happy and will do what it takes. That is one reason I go back to them. I did buy some shocks from them recently at great prices. Hopefully I will receive the correct thermosdat!

[quickbiker]

Mine came in, didn't even come with a gasket. Geesh.

[crew cab sonoma]

i`ve installed a 140 deg. marine thermostat in my truck, just to experiment with it...

stays right around 140 at night, but during the day (80 degrees), it slowly works up to around 155, or so...
but my fans are operating at very low speed... wired in parallel, drawing only 3.4 amps...

[killian96ss]

i`ve installed a 140 deg. marine thermostat in my truck, just to experiment with it.

You will almost certainly set the SES light because that t-stat temp is way too low for proper emissions.

Even the 160* t-stat usually sets the light.

You will also use more gas with a t-stat that low so your gas mileage will drop and you run the risk of pre-mature cat failure.

Be sure to let us know what problems you run into.

Steve

[crew cab sonoma]

on a 2001-later model, a 170 stat will set the low coolant temp code.
on my 2000, it has been through a week of daily driving with the 140, and still no code set....

as for cat failure, i really dont see how that would happen.
the engine consistently goes into closed loop at 133 deg., and remains there.... despite running at a steady 140 on cool nights.
this was verified with my scan tool...

my daughter`s 1990 Dodge Spirit 3.0L has had a 160 stat in it for almost 2 years now, and has passed 2 sniffer type emissions inspections, with flying colors... the converter is the original, with 160,000+ miles on it...

as for the fuel economy... i`ll let you know after a couple of tanks...

[killian96ss]

A cold engine will usually use more gas whether your in open or closed loop.

The PCM uses input from the IAT sensor, coolant sensor, and 02 sensors to determine the correct fuel trim.

Usually if the PCM gets readings that are too cold it will try to add more gas to compensate just like it does on warm up.

More gas in the mixture = more unburned fuel in the exhaust.

Unburned fuel reduces the life and efficiency of the cat.

If you use more gas to travel the same distance then your gas mileage has just dropped.

You would probably be shocked to see that your engine is making less power with the 140* t-stat due to less thermal expansion in the combustion chamber.

All engines require a certain amount of heat in the combustion chamber to make maximum power.

There is a reason why the 140* t-stat is used for marine engines only.

I run a 160* t-stat in my SS and can also pass emissions tests easily, but my computer has been thoroughly tweaked for this to work right and make more power.

I have never seen anyone run a t-stat in a Chevy V6 or V8 under 160* and make more power or gain gas mileage.

Steve

[HenryJ]

The additional wear when running too cold is something to consider as well.

Thermostat Theories and cooling system explained



A marine engine performs a different task and has different resources available. The engines can develop huge amounts of heat since they have a virtually unlimited volume of coolant. This allows for higher compression ratios and more timing.
They operate at a high fixed rpm primarily. There is no need for a broad powerband.
Even then a 140 stat may be too low for even a marine engine. As pointed out above, there needs to be enough heat for a complete burn. Optimum efficiency may not be met at the lower temperature. Cylinder temps around 300 may be better. I don't know what coolant temperature it will take to attain maximum power.

In a drag race situation the colder stat may be a benefit. My car makes the best times if I can reach the starting line at around 160 degrees. I run a 160 stat in it. I usually hit 190 on the return road. Most of the time on the street it runs 190-200 degrees. The stat is wide open after 160 and acts as a restrictor beyond that point. Airflow is the controlling factor after that.

Keep in mind too that the stat has a range. It is not 140. It starts opening sooner and is fully open after. A 140 stat may be 130-150. I think the threshold for the earlier 4.3L engines was 153. You might get away with that cold stat during the summer months. I assure you that a warmer stat will be much more comfortable in the winter months around here

[F9K9]

I'll wager a SES light in the cooler weather. I did before I re relocated my IAT with the Jet 180*

[quickbiker]

I know it's been a long time, but I finally got around to putting the 180 deg tstat in. I'm hoping it may help with my interittent AC, as I'm at a loss to what that can be. My AC has always been intermittent, some times worse than others, and worse when it's hot. I'm hoping lowering the eng temp may help. I know I'm drawing straws now, ugh.

[F9K9]

........... I know I'm drawing straws now, ugh.

I know the feeling. I removed my precat (ended up not being plugged) and early signs are that it has helped. This was done at the same time I replaced a Flex-a-lite Variable Speed Controller for the LS1 efans so, nothing is conclusive and it is VERY early. I will not be able to attribute a solution if, I am out of the woods on this one. Trial and error, as you well know, Paul!

[quickbiker]

No lights from the 180 deg, but I did fix my A/C.

Also, is it legal to remove the pre-cat if the cat is kept? I assume that's what you are talking about? I always thought those things are called resonators.

[HenryJ]

is it legal to remove the pre-cat if the cat is kept?

Probably not legal to alter the emissions system. If a visual inspection is required it may fail. If a sniffer and lack of light will pass you, you should be fine.