I sure need some advice!

This morning I finished putting my 36 truck's newly rebuilt radiator back in place, complete with a 14" 6volt electric fan which fits neatly in front of the radiator, just below the shell cross-brace. I added a thermo switch to run the fan when the coolant temp reaches 185 degrees. I also installed a 160 degree thermostat--there was no thermostat in it when I bought the truck. I got it all together, filled it with coolant, and ran it for 20 minutes in the garage--all was well with no leaks. I took it for a 5-mile drive, and the normally-overheating system behaved itself very well--staying just above 180 degrees.

A couple of hours ago I took it for a 2nd run, and on the way home the temp gauge hit the stop past 212. I made it home, but dicovered I had lost all the coolant. I let 'er cool down, and then added hot water to the radiator--which then began to pour out of the rear center of the engine. I thought I'd blown the rear freeze plug, but removed the floorboards and the plug is fine--the coolant is running out somewhere between the clutch housing and the engine below the plug, with no evidence of it coming from anywhere above the clutch housing. Oh, this is an original 207 engine.

Any guesses about where my leak is originating? I'm no engine mechanic, and I don't know where to look. Thanks for any help!

Wally

There should bejust one 1 1/2" plug at the rear of the block. Can't think of ant other possible places that low down. Could be the head gasket and the coolant is running down the back of the block or the temperature sending unit opening. I would refill it at watch where its coming from. The 1936 is a one year only as far as block cooling is concerned and I don't have a good picture ro refer to.

Gene,

No leak from the temp sender, or from above the 1 1/2" rear freeze plug. It could be the head gasket, although the engine was running and sounding normal (but damn hot!) when I shut it off. The coolant runs out very quickly from whereever it's leaking.
Any point in opening the pushrod cover? There does seem to be some seepage around the edges, but it could be oil due to the overheated engine.

I'll get my lovely assistant to pour some water in the radiator while I watch from below.

Wally:
If the water is not leaking from the rear freeze plug or temperature sending unit it has to be a head gasket or a cracked block. I doubt it would be a cracked block. I assume you shut the drain petcock on the side when you replaced the coolant. Removing the valve cover would not tell you anything. Gene's advice of locating the leak is the best way to diagnosis the culprit.
Richard

Richard, Yes, I did have everything shut tight when I took it for its 2nd ride of the day.

I just removed the cover plates from the bottom of the clutch housing, and had my wife pour about a quart of water into the radiator while I watched from below--about 15 seconds later water began to pour out of the clutch housing. This sort of negates the head gasket theory. I can not see water coming from anywhere on the sides or the top of the block--just where it appears inside the clutch housing.

I wasn't suggesting taking off the valve cover, but rather the right side cover.

Wally: I know it is a long shot, but could the head gasket be leaking on the back side, where it is hard to see, and running down the back side in to the bell housing? I should of read your posting more carefully! I see you said: pushrod cover and not valve cover. I don't think that would tell you much either unless you find a big crack there, which I hope is not the case. I will pull out my literature and see if it will jog my memory on where the water could be coming from.
Richard

Hi,

I am not certain about your engine, however a lot of engines have a freeze plug (expansion plug) located on the back of the engine. In some cases the bell housing covers 1/2 of the plug. This plug, if removed, would allow a great deal of water to escape in a very short time.

Does your bell housing have an inspection plate on the top? If so this would allow inspection before pulling engine or transmission.

Ray,
Thanks for your reply, but...

1. The rear freeze plug is intact and not leaking (I almost wish it was!)

2. I have opened the bell housing top inspection plate, and it reveals only that the clutch mechanism got a little wet from coolant leaking into the housing, but it seems to be dried out now.

I'm thinking I saw a post recently about some kind of plug in the pushrod recess--would that be to the coolant gallery?

Wally

I found the earlier post, but it probably does not apply as I don't think coolant is running into my oil sump. Here it is:

"I am not sure if this applies to your motor or not but some manufacturers put freeze (welch) plugs behind the pushrod cover, if 1 of these has rotted through it would dump cooling contents into the sump. I would be dropping the sump and pushrod cover for closer inspection.
Someone also made a valid comment on the possibility of head gasket deteriation as well. Basically water in the sump is not good for any engine and the cause needs to be rectified."

If there is water leaking into the oil the oil will turn a muddy white (if engine has been run) and the oil level will be overfull. Water leaking behind the side cover could be the fitting for the rocker arm oil line, head gasket or block crack. The oil line fitting could also leak on the left side of the block (leak water).

I dont know of any engine that has the head gasket below the bellhousing, there may be a freeze plug behind the flywheel as well as above the bellhousing that has had gunk acting as a sealing agent until the system has been flushed out. There was a discussion earlier that stated that engines about that model had cooling further down the block that would make the extra freeze plug a possibility.
Someone with 1 of theses engines or gearbox removed would be able to confirm or deny my theory. If this is the case I would be replacing all freeze plugs that have not been replaced in the recent past.
Tony

Wally,
Is the water that runs out fairly clean or does it look like chocolate milk? I'd start with a check of the engine oil level. It sounds like the sump is full and fluid is running out the rear main....not a good scenario as that's probably a cracked head or block.

Secondly do a compression test to see if you have a low cylinder or two. The precise psi is not important, rather try to see if one or two cylinders don't hold much pressure relative to the others.

Removing the engine side pan won't reveal much. A cracked block would be internal and probably not visible from the side.

Best of luck with the issue...and keep us posted on your findings.

Removing the side cover would reveal if the block rocker arm line fitting is leaking coolant....this "feature" was new for 1936. Leakage at this point is not totaly uncommon.

Thanks ChevGene, Coachhill, Richard & TonyW for chiming in on this...here are my "morning findings":

The oil color and clarity are normal, and the oil level is halfway between full and add on the dipstick.

The water we added to try to locate the leak comes out clear, and as near as I can tell it runs off the rear edge of the sump mounting ledge, which is visible from below with the covers off the clutch housing.

A 3rd leaking freeze plug would be a good solution--given the other unsavory options--but I can't see behind the bellhousing. Does anyone know about a 3rd plug on a '36 engine?

I won't be able to investigate further until next Wednesday because the "W" word (work!) will have me tied up today thru Tuesday, but I appreciate your continued thoughts and comments. Keep 'em coming!

Wally

Wally:
I have been thru everything I have, including pictures of my 36 block, but nothing shows the rear of the engine and I just can't recall anything other than one freeze plug at the rear. I hate to say it, but I think you are going to have to pull the engine to determine and fix the problem. Maybe someone has an easier solution.
Richard

Still hoping for someone to tell me if there's a 2nd freeze plug behind the bell housing on the 207. Thanks.

Wally

Coincidently, i have my 207 at Rick's Machine Shop in Santee, CA. for rebuilding (619) 562 - 8010. I called to ask him if there is a second freeze plug and he confirmed there is a one above the bell housing and another below (within). My block casting number is 836010-3. The date code is D-21-6. I don't have a photo to share but I may be able to get one when I visit the shop in the near future.

After hooking the generator field wire to the light switch , I don't think the charge rate changes when I turn on the lights ! It is charging , the same as if the field terminal was grounded to the case. Where have I gone wrong ? Thanks I know the answer, if I could just think of it !

How did we get from the topic of "Sudden Coolant Loss" to the topic of a light switch all in the same thread?

Anyway, does the light switch in question have a resistance unit to increase the output of the generator? According to the parts book the resistance unit is not supposed to be connected on the 1934 1/2 ton truck.

With the resistance unit type of light switch, when the lights are turned on the unit will full field the generator, which is the same as the fields being grounded to the generator case.

Dear 33_Chevy_Truck,

Terrific, thanks for the answer--it has to be the freeze plug I can't see that blew out! My engine number is 836010-5 with a date code of E-13-6. I'll follow up with a photo once I get the engine pulled.

Wally

Wouldn't it be easier to drop the transmission and bell housing and leave the engine in place?

winowally, check your sbc email. i sent you a photo of my 207 with the bellhousing off.

Mike,

Thanks for the PM and photo of your 207 at the machine shop. I'm inserting a link to it for anyone who'd like to see the entire rear end of a 207--with both freeze plug openings showing.

http://i292.photobucket.com/albums/mm24/winowally/207EngineBlock.jpg

I'm sure when I get my engine and bellhousing apart that lower freeze plug will be missing or out of position, causing my sudden coolant dissapearance! Hope I can help you out one day.

Wally

Gene,

I'm kind of at odds with that. There are some things I'd like to do to the engine out of the truck--like power wash the rust out when replacing the freeze plugs, replacing the mounts, and painting it (with FS Chevy gray, of course!). I'm not looking forward to taking the radiator and shell off again after just re-installing it with fresh chrome plating on the grille.

On the other hand, just dropping the trans and clutch does involve loosening the spring saddles and sliding the rear axle backwards after splitting the u-joint(at least that's what the trans shop had to do when I had it and the clutch rebuilt last year).

I'd appreciate any suggestions, as I've never had to do this before.

Wally

On a 1/2 ton truck with a 3 speed it is not necessary to slide the rear end back or fool with the U bolts.
Just split the U joint ball and unbolt the U joint, split the U joint and drop the torque tube. Unbolt the transmission and remove. A few other things necessary but this is the main part.
Do you have a shop Manual. The removal is described in there.