Help please

**River Beast** · 06-11-2002, 09:59 AM

Check your fan clutch... sounds like it's not pulling the air through the radiator for cooling...also check the weep hole on the bottom of the snout of the waterpump for weepage. Your pump can be on it's way out as well....

Have you tried backflushing the system? You could have some crud built up in the water jackets in the block.

Can't help you on the 727.. I have a TH400..sorry

Don't sell it just because of this...get it fixed and be a proud FSJer!!!

**steven79** · 06-11-2002, 05:15 PM

#1 put a thermostat back in it (factory temp one) I think they were 195 degress,that will let the water sit in the rad long enough to cool off and let the clutch fan work proprly.
#2 tf727's don't have vac mods they use a cable to the carb for shift points.

**Spinner** · 06-11-2002, 07:21 PM

How are your other shift points? If 1st & 2nd still shift at the previous points then you may have an internal problem with your tranny. What about manually shifting from 2nd to 3rd? Any probs there? If all of the shift points are now at higher mph/rpm, then you can adjust the shift linkage (looks like a Chebby kick-down linkage below your throttle linkage on the carb.). Tech section has a write-up on that procedure. Very important to set this shift linkage correctly or else you get much tranny clutch wear and much excess heat produced due to an over-revved motor.

**River Beast** · 06-11-2002, 11:03 PM

OOOPS!! I thought you meant you 'changed' out the the thermostat....yeah you need one for city driving for sure...

**J20fan** · 06-12-2002, 01:40 AM

I change out to 165* thermostat for the summer months. This keeps my engine temp at an excellent level in higher ambient temperatures. I also flush the system with a cooling system flush that removes scale etc. from the block.

**Dan G** · 06-13-2002, 09:57 AM

"Very important to set this shift linkage correctly or else you get much tranny clutch wear and much excess heat produced due to an over-revved motor."

Thanks Monster Mash!! Will do!

Also, will reinstall t-stat, though I might make a slight mod to it. Recently have been reading about adding a 1/8" hole to the flange of the t-stat to allow bypass if t-stat ever gets stuck.

Any thoughts??

**1BADJP** · 06-14-2002, 11:12 AM

Are you running a trans cooler or just the one in the radiator??
Install a HD trans cooler and run it through the radiator also.
try changing your trans fluid and filter--probably cooked fluid when overheated engine.
definitly check your fan clutch
You may need to install electric fan when plow is on to help cool radiator.
200,000 miles shouldn't be a problem if engine flow is good, look at flow in radiator while engine is running to see if it is flowing at all.
Do you know anyone with a laser temp gun??? they work real well and can pinpoint alot of system problems.
I wouldn't drill any holes in housing---if Jeep wanted one they would have put one!!!
GOOD LUCK

**Dan G** · 08-28-2002, 02:10 PM

Ok, reviving my old topic here...

1. I lubricated the TV linkage and readjusted it, tranny still operating poorly, won't go into 3rd until 60 and goes back in to 2nd shortly below 60.

2. 1BADJP, not drill hole in t-stat housing, drill hole in t-stat flange to allow a bit of bypass if element gets stuck. Has anyone done this?

3. 1BADJP, been looking for a reason to buy one of those laser temp guns. HVAC engineer by trade, maybe I can write it off as a 'work tool'!?!

4. Will changing out the valve body, fluid and filter cure my problem or am I in for a complete tranny rebuild.

5. If complete tranny rebuild, what's the going rate for a rebuild with the B&M manual shift valve body (2nd means 2nd and 1st means 1st) and HD clutches??

**gsmikie** · 08-28-2002, 03:24 PM

as for the trans shift point problem on the 727 there is a spring at the back of the intake that keeps tension on the linkage if the spring is gone/broken it will make the 3rd gear shift real late also the bushing in the kick down linkage at the bellhousing that holds the linkage cross shaft crack and fall out with age as for the over heat problem i would look at the fan clutch the lazer temp guns are cool as for the b&m man shift body and kevlar clutches and viton seals it runs about $600.00 for their kit

**ibnfe** · 08-28-2002, 03:31 PM

In my experiences on trannies, usually changing out the valve body with new will usually reveal all the other pending problems in the tranny. If you change the valve body and don't rebuild the tranny, you will probably need to within a short time. My 727 made it 'til 230,000 miles before everything started going south. As far as the rebuild goes, you can get all the consumable stuff for less than $250.00, and that includes a new converter. I do all of my own maintenance, so I can't help on how much it would cost to have someone else do it. Here's what the 727 tech manual says are probable causes for your delayed upshift: throttle linkage needs adjustment, kickdown band out of adjustment/worn/broke, worn seal rings, reaction shaft support rings worn, worn front clutch, governor problem. The first two are what I would concentate on first since they are easy and will avoid the rebuild if they work. Check/adjust your throttle linkage and the front band. If those and a fluid/filter change don't fix your problem, then it is internal somewhere.

**Wesdog** · 08-28-2002, 04:28 PM

Steven79 brought up the theory that:

[#1 put a thermostat back in it (factory temp one) I think they were 195 degress, that will let the water sit in the rad long enough to cool off and let the clutch fan work properly.]

*****************************************

There was a post a while back on the LT1edit list regarding the issue of flow rate through the radiator and I thought some on this list might be interested:

----------------------

According to Newton's law of forced convection, the amount of heat transferred can be represented as this:

Q=hA(Tw-Tr)

Where:
Q is the amount of heat in calories or BTM's or whatever unit you like.
h is the heat transfer coefficient for the system
A is the area of the surface where the heat transfer takes place and (Tw-Tr) is the difference in temperature between the coolant and the radiator (or the engine), i.e. delta T.

Nowhere does it mention the speed of convection. Because we're talking about identical setups except for flow, all the variables will be identical except for coolant temp. ***All that matters in determining how much heat is transferred is delta T, the difference in temperature between the coolant and the radiator.***

Let's look at two scenarios:

Scenario 1: 10 GPM coolant flow
Coolant temp coming out of the engine: 180 degrees
Ambient air temp: 100 degrees
Coolant temp as it comes out of the radiator: 120 degrees
Average delta T across radiator: 50 degrees

Scenario 2: 30 GPM coolant flow. Three times the flow, so the coolant is in the radiator 1/3 as long and loses only 1/3 as much temp per gallon:
Coolant temp coming out of the engine: 180 degrees
Ambient air temp: 100 degrees
Coolant temp as it comes out of the radiator: 160 degrees
Average delta T across radiator: 70 degrees

An average 70 degree difference vs. a 50 degree difference works out to 40% better heat transfer for the 30 gpm system, even though the drop in temp across the radiator is three times less than the 10 gpm system. Since the engine is going to be producing the same amount of waste heat in both cases, the delta T's for both systems must be the same. Therefore, for the second system, the coolant values would have to be 160 coming out of the engine and 140 coming out of the radiator. I realize it won't be exactly those values, but I'm not up to differential equations right now.

So despite the fact that the temperature drop across the radiator is less in the faster flowing system, you have 40% greater heat capacity for racing and on average your coolant temps will be lower. An added bonus is that because the coolant temp inside the engine is lower, you will be less prone to pinging and the computer will run more timing.

Now, why do you have to put a restrictor in the cooling system of an older smallblock to run without a thermostat? Well, it actually has nothing to do with thermodynamics, at least not directly. You can reference the faq at www.stewartcomponents.com if you want to verify what I'm saying, but the short of it is this: The restrictor isn't there to regulate flow, it's there to regulate pressure. The radiator is on the high side of the pump on older systems, and as the pump pressure climbs with increased flow, it will eventually push the safety cap open, even though it's not boiling over, causing a gradual loss of coolant and eventual overheating when the pump starts cavitating. That's all. The LT1's system has been re-designed so the radiator is on the low side of the system and not subject to high pressure. The only reason you even need a restrictor is to hold the gasket in place for the water neck.

Sorry if I rubbed anyone the wrong way, but you've got to nip disinformation in the bud before it becomes an urban legend.

Stonebreaker
-------------------------------------

What's this mean as far as FSJ's are concerned? It appears the thermostat not only regulates the engine temp, it also helps regulate the pressure the radiator see at higher rpms. It's not there to slow down the flow through the radiator although the stock thermostat certainly is a significant restriction. I use a high flow style thermostat that is available at most speed shops and through PAW. It is available in 160, 180 and 195 temperatures. They all have a couple of small bypass holes drilled in the housing to allow a small amount of heated coolant to flow through the thermostat so it will open sooner as the engine reaches the setpoint temp. When they are fully open they allow a significantly larger volume of coolant to flow through the system to the radiator than the stock thermostat. This type thermostat is also of a higher quality and less prone to failure than the stock ones. Hope this was of value to the list.

[ August 28, 2002, 11:29 PM: Message edited by: Wesdog ]

**Al Johnson** · 08-29-2002, 01:03 AM

Wesdog, I just love it when the math confirms my gut feeling on how stuff works. Never made sense to me to slow the flow of coolant to make it cool better.
Thanks for showing us the facts!
Al

**krob725** · 08-29-2002, 01:44 AM

You don't need to drill a bypass hole because it has a bypass hose already there.

krob725

**fredws** · 08-29-2002, 03:13 AM

Scenario 1: 10 GPM coolant flow
Coolant temp coming out of the engine: 180 degrees
Ambient air temp: 100 degrees
Coolant temp as it comes out of the radiator: 120 degrees
Average delta T across radiator: 50 degrees

Scenario 2: 30 GPM coolant flow. Three times the flow, so the coolant is in the radiator 1/3 as long and loses only 1/3 as much temp per gallon:
Coolant temp coming out of the engine: 180 degrees
Ambient air temp: 100 degrees
Coolant temp as it comes out of the radiator: 160 degrees
Average delta T across radiator: 70 degrees

An average 70 degree difference vs. a 50 degree difference works out to 40% better heat transfer for the 30 gpm system, even though the drop in temp across the radiator is three times less than the 10 gpm system. Since the engine is going to be producing the same amount of waste heat in both cases, the delta T's for both systems must be the same. Therefore, for the second system, the coolant values would have to be 160 coming out of the engine and 140 coming out of the radiator. I realize it won't be exactly those values, but I'm not up to differential equations right now.

Well, hate to bust Stonebreakers bubble, but. . . .

The heat transfer given in BTU/hr would be:

Q=M*Cp*deltaT

where Q is the heat transfer in BTU/hr
M is the flowrate, in GPM
Cp is 500 for water, of course with antifreeze it will be a bit different, but won't matter here as we are just compairing the two.
and of course deltaT is the difference in the entering and leaving fluild temp.

anyway, if you plug all that in for each case:

10*500*(180-120)=300,000 BTU/hr

30*500*(180-160)=300,000 BTU/hr

No difference.

Help please

Help please

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