Hot Rods Coolant leak from convertor drain

One of my hotrods is a model A coupe with a warmed up Chev 350. Lately it has started leaking coolant from the torque convertor drain hole. I can't figure it out and I wonder how serious this is. Will it heal up itself or is there something at the back of the engine that started to leak ? I tried the search forums but couldn't find anything. Any ideas

 

Freeze plug in the back of the engine block or intake at the back.

 

Any kind of leak rarely fix themself. Take a common paper towel and wipe the back edge of intake manifold to block and see if the towel comes back wet. If not, you're going to need to see the back of your block. On the other hand, maybe try some stop leak of some kind. I preferer a correct repair not mechanic in a can.

 

Thanks for the replies. I don't see how the coolant could get from the back of the intake down inside the torque convertor cavity. It is dripping from the inside of the cavity. The freeze plug in the back of the engine sounds more likely but I don't relish the fix.

 

one time I had that leak on my truck, at the drag strip. I borrowed a floor jack and pulled the trans back far enough to run a sheet metal screw through the hole in the freeze plug, put it back together, and won a trophy racing.

sheesh that was a long time ago!

 

Will the trans come down without interference of the frame?

 

Yes, but it is a heavy awkward thing. However, I think I know what I have to do. I wonder if it will last through this summer. I would rather drive it than fix it right now.

 

Summer isn’t exactly a good time to lose coolant.

 

Been there, done that not fun. At least in my case it was on a mid 70's two wheel drive Chevy truck that left it's green mark where ever it stopped.
This show and tell photo wasn't mine though.

 

Thanks for the picture. That makes it pretty clear where I have to look. I don't mind doing the job except for removing the transmission with a floor jack.

 

If you have brass plugs these most likely will get you thru summer. But if they are steel fix it correctly. https://www.summitracing.com/parts/...S8d8MYrsBrG2YephSAKhunjyPF74WFKCbaa2ZPHtZkpRE

 

There's an old saying "Choose your battles wisely" that could be amended to "choose your downtime wisely". Although it's not a pleasant (or quick) job, it's much better to do it at your choice of time, with time allotted to run for parts, con a strong friend into helping, being close to your own bathroom, etc.
Good luck!

 

I'd pull engine and transmission together then separate and repair.

 

My best advice here is, Do your homework and find the exact problem. Don't tear things apart with wishful thinking. Intake leaking and flowing down the back of the block seeping between the Block and Trans case does happen. It's a gravity thing and like electricity water flows the path of least resistance. I for sure would not pull a Motor and Trans out without knowing it had to be done.

 

Recently encountered a car that was maintained by a mechanic in a can. o/t car that had a leaky water pump and a small crack in the reservoir, girl only drove it a quarter mile every day so it never really got hot until she drove it 20 miles or so on a trip into town. her boyfriends fix? dump universal coolant into it and a bunch of stop leak. it plugged the rad solid. new water pump, new reservoir, 6 hours of flushing and a new rad fixed it... hopefully.

stop leak sucks.

 

Put em all in. Jim I also did the screw trick in a 383 mopar head. lol Lippy

 

Fortunately I have another classic ( my avatar) to drive so there is no rush into this thing. I will leave it up on blocks while I take Pist-n-Broke's advice and determine exactly where it is coming from first. I recently rebuilt the motor after a cam failure destroyed all the bearings . My machinist boiled out the block and reinstalled new frost plugs,etc. He is a very reliable guy but it is possible that one of the plugs has started to leak after a couple of seasons. Naturally it would have to be the one that is the most difficult to get to. I will try the paper towel trick to see if it is coming from somewhere else first.

 

Find someone with a Stant radiator cap tester, it has an adapter that fits on the radiator in place of the radiator cap, a few pumps of air and you'll find where the coolant is leaking from.

 

Is the trans cooler in the radiator?

 

Radiator trans coolers only leak trans fluid into the radiator. Not the other way around. The coolant would look like strawberry Nestle Quick then.

 

or dark brown sludge, either happens.

 

When you shut the engine down, the pressure in the radiator becomes greater than the pressure in the transcooler, and coolant can be forced into the cooler and back to the transmission. It happens often. Coolant in the transmission fluid is very hard on clutch plates.

 

Coolant pressure test will show where it's coming from of its not an obvious leak.

 

If the coolant leaks out of the convertor , wouldn't it also leak transmission fluid ?

 

My thoughts are that for it to be from the back of the intake/cyl. head area the coolant would have to go between the tight block/trans joint rather than run down the outside. Although it could run down the trans case and catch the lip of the dust cover. Most likely one of the freeze plugs. Drop the dust cover, get a flash light and maybe a mirror and take a look. Like mentioned above, a pressure tester will help.

 

Good idea on the pressure tester. Went out to the shop today and it hasn't leaked for 2 days. It has been just sitting though. I think the pressure tester idea is the way to go. The transmission cooler is separate from the cooling system so it is not involved. I tried the paper towel wipe at the back of the block and it came up clean. I will drop the torque convertor cover and see if there is enough space to look up through the gap between the convertor and the block. Then I will use a pressure tester if I can get one or start the motor and build up the pressure to see what happens. We are talking one or two drips a day though so there will not be a real river running to show the spot.

 

I believe he means the little hole in the cover.

 

Confirm with a pressure tester , as you stated take the converter inspection cover off and confirm the leak .
You could also put dye in the coolant and check with a black light .


If you have a decent tranny shop or a shop that does work on older cars , might be worth taking it there to get the job done .

if the trans comes out relatively easy it should only be a 4-6 hour job .probably less ( when I got into the trade 80’s rwd North America cars where about 30 minutes to pull the tranny )

might be worth spending the money then all those hours on your back wrestling a tranny , I hate big heavy jobs on my driveway under jack stands , usually takes twice to three times as long as doing the same job on a hoist .

 

Yup been there done that

 

I just got a block out of the shop, we’ll, month or so ago. I asked them to put in new cam bearings and brass core plugs. When I’d picked it up a quick glance the side plugs were brass. When I put it on the stand, the rear ones are steel/etc. WTF.
Anyways, back to the discussion.