• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Thermostat Bypass Blocker?

bowtiebutler956

bowtiebutler956

Active Member
Messages
581
Reaction score
207
Location
Harlingen, Texas
I have a question for the experts. I'm currently running a 180 high flow (Robert Shaw type) single t-stat in my 6.5, but it doesn't have the bypass blocker on it. What sort of problems can this cause. I'm in the process of updating my cooling fan, and radiator, and I want to have all my bases covered. My truck is a 93 6.5, and already has the late model high flow water pump. Here is the build thread. http://www.thetruckstop.us/forum/showthread.php?42774-Poor-Boy-Special-6-5-Refresh
I did a fair amount of searching here before I asked the question, but didn't really find an answer. I did read that there are 2 different length bypass blockers, and that the GM 180 is very hard to find. SSDiesel appears to have an aftermarket 180 with bypass blocker, but I don't really trust them.
Any help is appreciated. Thanks

Matt
 
Burning oil said:
I only run a 195* whats the advantage behind running a 180?
Click to expand...

Nothing, 195 is better all around. To the op, without a stat with a blocker you will never get full flow through the radiator. It will be like the dual stat housing, but with less area to allow flow to the radiator since you only have 1 instead of 2 stats. And they have found that even the dual stat housing needs a restrictor to get enough flow through the radiator.~
 
Burning oil said:
I only run a 195* whats the advantage behind running a 180?
Click to expand...
I live as far south as you can get here in the States, and our summers are hot. These 6.5's seem to be quite well know for damage, and cracks due to heat. I know the engine is more efficient at higher temps, but I would rather lower its operating temp by having a 180 t-stat, and an early engaging fan clutch, along with the rest of the cooling system being good enough to maintain the lower temps. Its just added piece of mind for me. Thanks

THEFERMANATOR said:
Nothing, 195 is better all around. To the op, without a stat with a blocker you will never get full flow through the radiator. It will be like the dual stat housing, but with less area to allow flow to the radiator since you only have 1 instead of 2 stats. And they have found that even the dual stat housing needs a restrictor to get enough flow through the radiator.~
Click to expand...

Thanks, thats exactly what I was looking for! I appreciate it.

Matt
 
The 180* won't keep it from overheating any better than a 195* would. The 180 just opens sooner. If you have a cooling issue that causes the engine to get hot a Tstat won't help. Thats why I only use 195*s.
On my 96 going from 180 to a 195 got an almost unbelievable 2-3 mpg improvement too.
That my experience anyway you got do whats best for you.
 
Burning oil said:
The 180* won't keep it from overheating any better than a 195* would. The 180 just opens sooner. If you have a cooling issue that causes the engine to get hot a Tstat won't help. Thats why I only use 195*s.
On my 96 going from 180 to a 195 got an almost unbelievable 2-3 mpg improvement too.
That my experience anyway you got do whats best for you.
Click to expand...

I hear what your saying Leroy, and I realize a 180 won't keep it from overheating any better than a 195 if there is a problem that is making it overheat. It seems the back cylinder have a tendency to run warmer do to coolant circulation issues, even if your gauge doesn't show it to be running hot. I'm running the 97-98 higher flow water pump which is supposed to be better, but from what I understand still isn't a cure for the problem. The way I see it, even if my back cylinders are running warmer that the rest of the engine with the 180 stat, they're still running cooler than they would with the 195. Or at least thats the way it works in my mind. :rolleyes5:

Say Leroy, is the OE stat a 190 or 195? I thought it was a 190.

Matt
 
Pretty sure factory is 195. Running cooler is NOT helping you in ANY way. MANY have tried it, and the 195 ALWAYS wins.
 
Well... on the 180 vs 195 issue:

I had 180 stat in my Hummer when I bought it, it ran 185. I replaced it with a 195 AC Delco it runs about 200. The extra 15 degrees is about 2 minutes of climbing temps going up freeway hills in the valley. I could go from Vegas to Boulder City uninterrupted. Now, in temps over 100 degrees I have to pull over and wait a few minutes to let the ECT come down off 220 on those same hills. If it is over 110 outside and I get off work currently about 4pm, I have to wait 15 minutes or so at the top of the hill before heading home. And yes I slow down to 50-55 mph in the 65 mph zone pissing everyone off. The 180 Robert Shaw will unfortunately not fit my Hummer or 1 would be in it now. The AC Delco 180 for it was discontinued.

You guys in the pickup only think you have an air flow over the stack problem until you deal with the crap design of the angled cooling stack worse than Corvettes. Not playing down the stack problem of a gmt400, but you have a issue, I have a problem.

In most situations, I agree that the 195 is way better, and definitely can get better mpg if your climate wont keep the temps up. If you are in a dry, hot climate it is a different story. It is not just the Hummer problem, that just exasperates it. In the fleets here there are a few things we did to brand new trucks like ripping out the junk heater hose quick connect on the crossover (or intake manifolds if gas). ALL the 6.5 trucks had the 195 stats thrown in the trash before it went into service or it was guaranteed to eat a head gasket or head before the end of summer. A company truck does not get the temp gauge looked at they just go, and when it blows up they get paid to sit on the side of the road. Every truck that went in to service ran a 180. 3 of the 4 GM dealerships swapped them at time of sale for fleet customers free of charge. We just asked for the free part and did it while we prepped the truck ourselves.

If you live in a climate where you can run the 195 definitely do it. But if you are looking at the temp gauge on every hill in town, I say try the 180 and test the difference for yourself. Easy swap and like what $20-$30? I'd GLADLY pay $100 to get a new low pro, high flow 180 AC Delco stat for my Hummer.

No fuel savings for me going to 195, but then again that's not too surprising with the brick that I drive. I have a friend in town w/ a 98 burb 6.5- he uses 180 June-September, then 195 rest of the year and gets 1.5 mpg better from it.
 
Has anybody done a pictorial of a bypass?

Matt, if you *really* want to run cool, drop in the 160F thermostats :hihi: My shop did that to me last winter and it made for a chilly ride in the mornings ;)

When I shopped for thermostats earlier this year, 195's were difficult to find and finally found two on eBay. 190's were much easier to find.

Interesting thing about the 195* thermostats is that the only time I am seeing ~190 ECT is when ambient is 95F+ with the A/C On. When ambient is lower than 90F, ECT is running ~175F which has me a little stumped. Maybe one of the new T-stats alredy failed open? :dunno:
 
The 180 F is all I run.

The 180 starts to open at 180 and is fully open by about 190.

The entire idea is to get the coolant flowing through the radiator as soon as possible.

These engines run hot anyway and other than the emissions, the engine is better off to be run a tad cooler.

If the fan clutches were set to lock up when the engine temp is about 200-205, life would be good, but generally they will not really start locking until the gauge reads 230, and this is too hot.

GM deliberately recalibrated the clutches to a higher engagement because customers were bitching about the roar.

A stupid mistake, but that's how it is.

Getting the DMAX fan/clutch on the engine will help a bunch.

Having the stat with the bypass blocker plate is the only way to fly.

Getting the fan working when it should is the secret.

Also, the radiators on these trucks are very close to marginal at best, especially in hot weather.
I have watched my temp gauge climb to 230 F on a hard pull and the fan not engage until I let off the throttle and allow the engine RPM to slow down, then the fan roars and the temps plummet back to 180 F

Just a bad deal all the way around.


At one time I tried a direct connected fan, and the beast never ran hot, never.

The noise was terrible though.

One much overlooked issue with these trucks is the condition of the radiator.
The radiator may look clean, but deep in the core the tubes start getting a coating of crud inside, that although it is thin, it insulates the surface of the water tubes, and really compromises the ability of the radiator to reject heat.

When you add up all the little issues with the entire cooling system, its no wonder there are heating troubles.


I had a 1993 club cab 2500 4x4 with a 6.5 and it never had heating issues, even in hot weather, but it was new, and I traded it for a dually truck when it had 35000 miles on it.

In review

The 180 stat just gives an already weak system a little less load to worry about.

If your radiator has more than about 75k miles on it, it's suspect, and if it has 200k or more, it's used up.


Visteon makes an OEM replacement for these rigs that has an aluminum brazed core that is just like what the truck came with new.

Several replacements being sold have an epoxied core, meaning the tubes are set to the head plates with epoxy. Read this as JUNK

Also be sure to keep the bumper nostrils open and the factory baffles intact.

The nostrils and baffles make a huge difference in the airflow through the cooling stack, mainly at road speed.


Missy
 
In the single t-stat system the "bypass blocker" is the second valve thingy on the bottom of the thermostat that stops hot water from being sucked back into the water pump from the crossover. If your single t-stat system doesn't have it you have the wrong thermostat.

When dealing with the delays to get the obsolete spring thermal fan clutch locked in you are best in high load or high outside temp situations to start with a lower peak temperature. I'll explain (and a review for others.) Because without the fan running all your engine and radiator is is a big heat sink.

When you mash the throttle to the floor and keep it there say to pull a grade that goes for miles you start the timer and start heating things up.
The thermostat is likely not full open so first delay is waiting for it to open up. ECT is climbing quickly mind you.
The next short delay is waiting for the radiator to heat up and a bit of a cold shock as the cold coolant gets up to temperature. (The bypass and heater core plumbing soften the shock.)

Then the ECT is simply going to climb until the fan kicks in:
The thermal coil spring has to get hot enough to move the valve in the clutch.
The fluid movement in the clutch will lock it in. It can take up to 2 min to kick a clutch out. The time to kick in is less.

Finally after all the above delays you have the fan kicked in to keep the ECT the peak temp or in some conditions bring it back down.

Starting with a lower temp thermostat means the peak temperature of the system is lower before the fan gets with the program.

Even with a low temp Kennedy Diesel fan clutch I would hit 210 on slight grades I didn't go WOT on. Going WOT kept the peak temps lower for some reason. Absolutely I used a 180 t-stat with a blocker. (Water wetter, HO pump, single 180, new or rodded radiator, new condenser with no bent fins, Kennedy Diesel fan clutch, 21" Dmax fan / 20" 9 blade steel fan.)

Don't get me started on what a cold engine does to AC performance when the "engine radiator" heat sink keeps the fan from coming on when the condenser is overheating. No room for an electric fan to assist...

I get interesting results running a heater core flow block valve for colder AC. The peak temp climbs more then goes back down during warm up. I am running a 190ish t-stat now and, no, haven't seen any MPG gains unloaded. Fans runs anyway for AC and high outside temps...

I would be curious as to why the HUMMER has more issues with the "screech - roar" solid lock up fan clutch? What ECT does the fan clutch lock in?
 
Fan clutches are low tech hassles on all engines.. Has anyone ever grafted on an electric lockup fan clutch from a big rig? Then you could just run a 200° temp switch.
 
Its seems to me the 180 is a band aid. It helps to mask another problem. With that said though if the 180 works for you....gotta do whats best for your sistuation.

Im going to what some might call extreme by relocating the oil coolers to remove that heat load off the radiator ( I guess its a form of band aid too?) http://www.thetruckstop.us/forum/showthread.php?43105-Engine-and-trans-oil-cooler-relocated

Will, I was just talking with a customer a few days ago with a Hummer. He was saying he would like to relocate his oil coolers too. Seems to me it could only help. My problem is having it here to do the mock up on. If I do get it for a few days I'll let you know.

WW and Missy, just thinking out loud. What if you could artificialy heat the fan spring engaugment "thingy" and use it like a resistor. Apply a modulated current to it that would be controlled by the temp switch? It could be a passive system, but install a switch to activate the fan anytime you wish.
I know simpler said than done (maybe:33:)
 
Scottm, I was typing my last when you posted. I was kind of saying the same thing but it would be nice if a kit could just be added to existing hardware.
 
scottm said:
Fan clutches are low tech hassles on all engines.. Has anyone ever grafted on an electric lockup fan clutch from a big rig?
Click to expand...

IIRC, Missy did.

Back to the question on blocking the port . . . Anybody have pictures to make it easier on somebody like myself???
 
At one time I thought about an electric fan clutch, but never got it past the thinking stage very far.

If the thermal clutch will come on at a low enough temp, then the system will work fine.

I want that fan to roar if the temp of the engine reaches 200 F

I am told that the Hayden Severe Duty units are calibrated lower than the factory units that they replace

Anyone using one.

My clutch on Dahooooley is likely the one it left the factory with, and at 188k it's probably used up.
 
I swapped an engine about a year ago for a friend. I could not get the ECU to do a timing set. It refused. Till I realized some nucklehead had put 160 deg stats in it (dual). Dropped in two 195s' and Bobs your uncle. Even with 180s the ECU thinks the engine is never warming up and does not get into the normal operation part of the fuel map. You cant fool the computer. Diddling with stat temps is very old school in these electronic days and nothing good can come from it in any setup close to stock. A holdover from the early days of EPA mandated pollution controls that were crappy.
 
L98TPI said:
I swapped an engine about a year ago for a friend. I could not get the ECU to do a timing set. It refused. Till I realized some nucklehead had put 160 deg stats in it (dual). Dropped in two 195s' and Bobs your uncle. Even with 180s the ECU thinks the engine is never warming up and does not get into the normal operation part of the fuel map. You cant fool the computer. Diddling with stat temps is very old school in these electronic days and nothing good can come from it in any setup close to stock. A holdover from the early days of EPA mandated pollution controls that were crappy.
Click to expand...
I don't have to worry about any of that, as my 6.5 is fully mechanical, and has no type of emission equipment. :)

Matt
 
You must log in or register to reply here.
Back
Top