700r4 Overheating

[AusTx68]

So when I installed this tranny I did not have the tv cable properly set. I didn't realize this until 100 miles later. I then went back and corrected it. Since then it has been running fine (maybe 75 miles). Then all of a sudden it starting overheating. At first I thought it was my motor. Later I realized the fluid temp was so high that it was overheating the water in my radiator. I was on the road when it happened. If I threw it into neutral and brought up the rpms it would cool down. When I hit the road again it would heat up in less than 5 miles. If I sit and idle the temp stayed normal. I'm confused as to why this started happening when it was running fine after I set it. I guess it could have been overheating but only now is getting high enough for me to realize it.

[SSedan64]

Is the TCC/TorqueConverterClutch lockup connected? If not this can cause overheating in 4th-O/D.
TV Cable not set correctly? Too loose?
Material from slipping clutches can plug Filter and Trans cooler & cause overheating.
You can compare the flow at Radiator of the Cooler feed line "upper" to the Cooler return line "lower" to check for blockage. A Funnel with a long hose attached to dipstick tube is needed to prevent low fluid condition. Check with Trans warm, idling @1000rpm no longer than 45-60 seconds running time as return line goes to Trans lube circuit.

[clinebarger]

I agree with SSedan64. But a 700R4 will usually vent fliud when overheated, Is it venting fluid? How do you know your trans is overheating, Are you verifying this with a gauge?

Its a good idea to run a auxiliary transmission cooler along with the radiator mounted cooler in any performance application.

[AusTx68]

Originally Posted by SSedan64

Is the TCC/TorqueConverterClutch lockup connected? If not this can cause overheating in 4th-O/D.
TV Cable not set correctly? Too loose?
Material from slipping clutches can plug Filter and Trans cooler & cause overheating.
You can compare the flow at Radiator of the Cooler feed line "upper" to the Cooler return line "lower" to check for blockage. A Funnel with a long hose attached to dipstick tube is needed to prevent low fluid condition. Check with Trans warm, idling @1000rpm no longer than 45-60 seconds running time as return line goes to Trans lube circuit.

Lockup is fine. I have a B&M lockup kit and it works great.

Originally Posted by clinebarger

I agree with SSedan64. But a 700R4 will usually vent fliud when overheated, Is it venting fluid? How do you know your trans is overheating, Are you verifying this with a gauge?

Its a good idea to run a auxiliary transmission cooler along with the radiator mounted cooler in any performance application.

So where does it vent fluid cuz I damn sure have a leak. Also I'm running a frame mounted cooler.

I can tell it's overheating because he hot fluid going thru the radiator is causing the engine to overheat. I only happens when driving in 3r or 4th gear for about 5 miles. Then my temp will climb rapidly. If I throw it into neutral and rev the motor will slowly go down. At first I thought it was my motor which didn't make sense because all the components are new (coolant, thermostat, pump, aluminum radiator). To be certain I swapped out thermostat and flushed the radiator. Same problem.

Today I pulled the tranny for planned maintenance. I've been running a 3000 stall (long story) but today I put in a B&M 2000 stall converter. That should help keep temps down. I was just about done when I broke the speedometer driven gear housing. Tomorrow I'll install a new one along with a new filter then take her out for a road test.

[tonypaul]

I have never heard of a trans overheating a motor. If the fluid has reached those kind of temps your clutches would be fried. I really think you have something else going on.

[Richard H.]

You do know that rad cooler is nothing more than a tube maybe 3/8 " going from hole to hole. Doubt that is going to over heat the radiator.

[AusTx68]

I once read it can occur which is why I suspected it was happening. If I allow my engine to idle it will not overheat. If I rev to 2500 rpms and hold it while parked, it will not overheat. If I hit the road with a warm engine and cold transmission it takes longer to overheat. But after the first occurance it happens again within 5 miles of driving.

If it's not the tranny then I have no clue. All the engine components check out good. I have no heater core, no leaks and coolant level is good. At one point I wondered if my lower hose is colapsing. When I had the coolant flushed it collapsed quite a bit. Shouldn't there be a spring inside to prevent that from happening? That hose is the only thing I did not replace during my build!

[cableguy0]

IF the transmission was getting hot enough to cause the engine to overheat that truck would have stopped moving a long time ago. The clutches would be cooked and the fluid would be dark black and smell burnt. Im gonna bet its actually the engine overheating.

[AusTx68]

This is frustrating..I used to have trouble keeping it above 160 degress while cruising! I can't recreate the problem while parked. I have less than 300 miles on this motor and all components are new.

I will starting focusing on the engine as the cause and recheck everything. Just to be sure I will route the tranny lines away from the radiator and run it only thru the cooler and see what happens.

I think I'll replace that lower hose as well. It could be colapsing when the engine is at speed.

[AusTx68]

The more I google the collapsing lower hose the more I think that may be the problem. There is supposed to be a spring in the lower hose to keep in from collapsing. That old lower hose I'm using doesn't have one. I will not mess with the tranny lines and just replace the lower hose. Hopefully that's the problem.

[Captainfab]

If you're running one of those frame mounted coolers, that likely isn't doing you any good. A trans cooler needs air flow to transfer the heat. This is why you typically see them in front of the radiator, or else with an electric fan on the cooler.

[AusTx68]

I mounted it on the front of the forward cross member just below the radiator. I know this is not as good as having an idependent fan or being on the radaitor but it should help some when moving. It's setup in series with the radiator.

[vasquezmrysvll]

iv had the lower hose collapse on my 85 iroc, threw TONS of parts at it.... someone told me about the "lower hose " problem, revved the engine from under the hood while watching the hose....sure enough it closed at about 2500rpm.

[tonypaul]

Very well could be the lower hose... Just think about whats happening here... At normal speeds your truck will over heat, if you increase the engine revs- thus increasing the water flow speed through the radiator it cools down. Some things I would double check-

No air pockets. Once the truck overheats once a air pocket can stay there. Jack your truck up from the front as high as you can and fill the radiator slowly. take off the upper hose at the water neck and remove the thermostat and wait for it to fill. Look for bubbles at the top of the intake where the thermostat goes. Once its full squeeze the bottom hose and watch for bubbles.

Correct pulley sizes- too small of waterpump pulley or larger crank shaft relationship can cause over heating.

Thermostat- even though it may be new, it can be faulty. put it in a small pan of water on the stove and turn the heat on, watch to see it open, turn off the heat and watch it close.... Make sure its opening all the way!!

If that dont work drop it off at my house with the title and keys and I will take it!!!!!

[tonypaul]

Joesph you get the truck fixed???

[AusTx68]

Nope. Still running hot. I think there must be an air pocket behind the thermostat. I have an electric fan that senses temperature with a thermal rod that's pushed thru the radiator near the top hose. When the engine runs hot I noticed the electric fan is not running. It's set to kick on at 180 degrees. That tells me the thermostat is not opening. The gauge is reading 220 and the fan is off. If I quickly rev the motor it starts to come down and the fan kicks on. I know the gauge is correct because as the temp spikes coolant start spewing out from under the radiator cap. It's definitely overheating. Tomorrow I will drain the system, replace the lower hose, drill a small hole in the thermostat to allow air to escape, reinstall and refill the system with the front of the truck elevated. If that doesn't work I'm doing to shoot it!

[AusTx68]

Ok, so I think the problem is worse than I thought. Perhaps a blown head gasket. I've checked everything with the cooling system. Replaced thermostat, radiator cap, flushed system, elevated front of truck during refill and made sure it topped off at the thermostat and sensor openings. Started engine and waited for thermostat to open then topped off with water. Took it for a drive. Within 5 miles it started overheating and I have a white frothing foam at the cap. Let it cool then drove home. Left engine running and checked coolant level. It was down 6" into the radiator. Topped off again while running and allowed it to overflow to remove foam. Took out for a drive. Again it got hot. Drove home and check coolant level while running. Again, coolant was low in radiator and there was lots of white foam. No water in coolant and there doesn't appear to be oil in the water. Any guesses???

[stich626]

check ur timing

[AusTx68]

Originally Posted by stich626

check ur timing

Timing? Timing has not changed.

[tonypaul]

Try running it with out a thermostat, start it up and check to see if you have good water flow with the cap off. Does your tailpipes have any moisture coming out?

[tonypaul]

Will it over heat at idle or is it only when your drive it?

[AusTx68]

Originally Posted by tonypaul

Try running it with out a thermostat, start it up and check to see if you have good water flow with the cap off. Does your tailpipes have any moisture coming out?

I will try removing the thermostat and see what happens. I didn't notice any moisture at idle but it doesn't overheat when idling.

Originally Posted by tonypaul

Will it over heat at idle or is it only when your drive it?

After filling it I let it idle and watched as the thermostat opened, the fan kicked on and it idled without getting too hot. Start driving it and it doesn't take long to overheat. There is a lot of pressure in the cooling system when it does. I'm going to test the coolant with a combustion leak detector. Hopefully I can rent one from a local parts store. If not I'll have to buy one.

[cableguy0]

Pull all the plugs. If your running straight coolant one will have a green tint to it. The combustion gas tester is the best way to go. The tool itself is like 40 bucks online and comes with fluid. If its building a lot of pressure,loosing coolant,foaming and overheating Its a fairly safe bet that pulling the heads is in your future

[AusTx68]

This morning I removed the thermostat and refilled with straight water. At this point there is little no coolant. Just pure water. While running I pulled the cap and topped off the radiator. Water was clearly flowing. I let it idle until the temp hit 175 then adjusted my fan to kick in at that temp. I then hit the road. Once I got moving the temp dropped below 150. I put 20 miles on her and the temp never went above 150! Stayed around 145. I drove back home and pulled the cap. Coolant was down a little so I added more water. There was less foam this time. I let it idle to 175, the fan kicked on and the temp never got higher 175. Hit the road again but this time driving slower country roads with more stops. The motor never got hotter than 160. The fan never kicked in until I hit my driveway and let it idle. At this point I pulled the tab on the radiator cap and it released a lot of pressure and foam. Once the pressure released I pulled the cap and could see water flowing. There was lots of foam. I'm wondering if the foam is from the Preston Super Radiator cleaner I dumped in a couple days ago. I thought I flushed it all out but there may have been some left over.

At this point I feel pretty good. The motor didn't overheat and it felt strong. Now I will drain the water and refill with 50/50 water coolant and leave the thermostat off and keep and eye on it. The truck is not a daily driver and will see little to no time during the colder part of a Texas Winter. Btw, the only other thing I did was tighten my power steering pulley. I noticed it was wobbling. Not sure if that helped.

[tonypaul]

I bet all that foam might have been causing air pockets. Just flush, flush, flush.... Stick the water hose in the top radiator, take off the lower hose at the radiator, turn on water full blast- start truck and rev alittle off an on.... Let it rinse for awhile.. If you plan on going ot the track anytime soon, just run straight water, if you just plan on killing everything on the street- add the coolant!!!