C4 Trans blows fluid out dipstick

[Matt760]

Basically my problem is this: After running my truck for a little while and shutting it off the trans fluid overflows out the dipstick. Have any of you encountered this on a race vehicle before? I think when you have 2 trans coolers mounted up high above the dipstick then when shut off they unload themselves and spew out over the dipstick and land on the headers causing a fire! Happens almost every time I shut off the truck and only started doing this after I added the second cooler. I have dual filters plumbed correctly and they act as one way valves so the fluid is just going back into the trans normally not back-flowing. I thought of maybe sealing the dipstick and add a reservoir with fill cap up higher, you know those big aluminum reservoir canisters with -an fittings all over them, one of those. Anyone ever expierence this before? Its pretty sketchy shuting off the truck and running over to blow out a fire everytime. How do the class 7 open and 8 trucks do it? I know alot of them have the coolers just like mine... any input is appreciated, thanks Matt Torian 1481

[Matt760]

picture for refrence

[Josh_K]

I am no expert on autos but your idea that the cooler is bleeding off and fill the trans is plausible.

On my 8 truck that doesnt happen but if you turned the cooler so the fitting are on the top I think it would stop the bleeding. If this fixes it then you know what the problem is. If it doesnt then its not.

Josh

[Dave_G]

Put a check valve in the line.

[hoeker]

this shouldn't be a problem if everything is plumbed right. sounds like you have conventional oil filters between the trans and coolers. these will prevent back flow and if you're filling the cooler from the bottom like you should be it won't run out the top. i would check to make sure your vent flows freely, this sounds like the problem to me.

on a side note, i have successfully run engine oil filters on my trans, but change the filter often. i eliminated them at the request of my trans shop and now run an oberg just to keep the big chunks out of the coolers if i junk the trans.

[ntsqd]

C-4's seem to have a history of this sort of thing in Early Broncos.

If the coolers are mounted with one port above the other make sure that the return is out of the top. If the ports are horizontal make sure that they are on top and not on the bottom.

GM sells a dipstick that has a toggle handle. Flipping it over locks the dipstick into the tube by expanding the rubber seal. They are remarkably inexpensive. I would alter one to read correctly and use it.

If after all of that the problem still persists make a catch can with a filtered vent on top. Braze or weld a bung onto the side of the dipstick tube and plumb the vent up to the catch can. You want the can to be above the bung on the tube with no low spots in the hose so that the fluid will drain back into the trans. Note that some tubes have a little vent hole near the top, this will need plugging if you opt for a catch can.

[Matt760]

Thanks for all the responses, alot of worthy fixes, Im going to look into the lockig GM dipstick. I need to check my vent, Its somewhere on the top of the housing so space is pretty tight against the cab, I might not even have one up there or it may be plugged up. And the lines are plumbed how you guys requested, the fluid enters the dual filters (ph8's), then to the bottom of the first cooler, out the top and into the next cooler at the bottom, out the top and then back to the trans. The catch can idea is a good one also. Ill do that if everything else fails. thanks again

[hoeker]

the bronco graveyard stocks a c-4 dipstick with the locking lever. no hassle getting the correct fluid level if you buy it this way.