TH400 Modulator Valve

[lusktommy]

if it was water from like a head gasket blow it wouldnt just do it on start up it would continue to do and you would eventually start getting a miss due to a plug getting water in it, and she would continue to blow steam out the exhaust. so process of elimination says tranny fluid getting sucked into the intake from the vacuum line....anyone not agree?

 

[foamypirate]

if it was water from like a head gasket blow it wouldnt just do it on start up it would continue to do and you would eventually start getting a miss due to a plug getting water in it, and she would continue to blow steam out the exhaust. so process of elimination says tranny fluid getting sucked into the intake from the vacuum line....anyone not agree?

I would disagree, sometimes a mild headgasket leak will be slow enough that you only have a stumble and a cloud on initial startup, as it burns off coolant that collected overnight or while it was parked, and then runs fine afterward until it's shutdown again. I've seen a few cars with this type of failure.

 

[lusktommy]

I would disagree, sometimes a mild headgasket leak will be slow enough that you only have a stumble and a cloud on initial startup, as it burns off coolant that collected overnight or while it was parked, and then runs fine afterward until it's shutdown again. I've seen a few cars with this type of failure.

true you could always rent a radiator pressure tester kit from you local part store and see if you are getting compression in the radiator, but that is if the modular doesnt fix the smoking problem.

 

[DoubleDingo]

When I asked about the smoke I also asked about the modulator only allowing a little ATF through. Was told it would keep sucking ATF if the modulator diaphragm was bad.

I replaced the modulator and it shifts like it's supposed to. The truck actually seems to run better with the new modulator valve on it. Definitely like the new shift points.

I do appreciate the input guys. Fortunately, the truck isn't showing any signs of head gasket problems and isn't leaking any fluids. I think I got lucky on this $1,000 truck.

The truck did sit for long periods because the guy didn't like it and only used it for dump runs ever now and then. It does only smoke upon start-up and then quits a few seconds later. I need someone to start it while I stand at the tailpipe so I can evaluate the color and smell of the smoke. And it does start immediately. Turn the key and instantly the truck starts. Even though it started like that from the beginning, I have ran some Motor Purr through the fuel system to help clean the carb. As soon as I get two locking gas caps and fill both tanks, I plan to take it on a good road trip to blow things out.

Next on the list of to-do's is a carb kit and do at least three drain/refill of ATF and then the filter change. The truck doesn't stumble, miss, or show any signs of a blown head gasket. It just smokes a little and then runs strong and smooth. Antifreeze doesn't have oil in it, and the oil doesn't have antifreeze in it. The truck just needs a few minor tweaks and replacements of old original parts and this truck will be good to go.

 

[HotRodPC]

I'd say the valve seals likely hardened up a bit since it sat for some time. With use, they just might resoften eventually, but even if so, they'll probably be short lived. If that's all it is though, knowing the truck sat and that's the reason the seals maybe stiff, and not wore out, then I'd just rock with it and expect that little puff of smoke for the first start up of the day. Doesn't sound as if it's enough to foul plugs or have to add oil between oil changes depending on how often you change it, so I wouldn't worry about it, and I'd rock it !!! Does sound like a good deal for $1000 for sure.

 

[lusktommy]

When I asked about the smoke I also asked about the modulator only allowing a little ATF through. Was told it would keep sucking ATF if the modulator diaphragm was bad.

I replaced the modulator and it shifts like it's supposed to. The truck actually seems to run better with the new modulator valve on it. Definitely like the new shift points.

I do appreciate the input guys. Fortunately, the truck isn't showing any signs of head gasket problems and isn't leaking any fluids. I think I got lucky on this $1,000 truck.

The truck did sit for long periods because the guy didn't like it and only used it for dump runs ever now and then. It does only smoke upon start-up and then quits a few seconds later. I need someone to start it while I stand at the tailpipe so I can evaluate the color and smell of the smoke. And it does start immediately. Turn the key and instantly the truck starts. Even though it started like that from the beginning, I have ran some Motor Purr through the fuel system to help clean the carb. As soon as I get two locking gas caps and fill both tanks, I plan to take it on a good road trip to blow things out.

Next on the list of to-do's is a carb kit and do at least three drain/refill of ATF and then the filter change. The truck doesn't stumble, miss, or show any signs of a blown head gasket. It just smokes a little and then runs strong and smooth. Antifreeze doesn't have oil in it, and the oil doesn't have antifreeze in it. The truck just needs a few minor tweaks and replacements of old original parts and this truck will be good to go.

good to hear!! congrats on getting a great deal on a square