75 eldorado coolant leak under engine

[Doug Spingelt]

the Cadillac lost all of its coolant the other day on the freeway and I assumed it was the lower radiator hose based on the speed at which it drained.  I replaced that, which was definately needed, but turned out not to be the issue.  when I pour water in the system to test, it litterally runs out the botom on the motor, seemingly above the front "trans-axle/transfer case" under the motor.  I cannot tell where this is comming from, even with the car on blocks and watching it run out. 

Can someone tell me what is there that can burst with the cooling system? 

As a short history. I have new radiator and hoses.  I also know I have a leaky freeze plug, but in the back of the motor and have been waiting to repair with the exhaust manifolds, which wil not seem to come off.  could this be that plug?  it seems not to be in the right place for the leak though. 

Thanks for your help!  I will probably tow it to a shop tonight as I am stumped and don't have much ability to work under the car. 

[Otto Skorzeny]

Hard to say without looking at it but if it's pouring out as soon as you fill it - and not just when the engine is running - it's likely coming from a water pump and/or water pump gasket. Hopefully you don't have a cracked block.

Did the car do anything else besides lose all it's coolant? How did you discover that the coolant had leaked out?

[Walter Youshock]

Sounds like the water pump bearing seal is gone and the coolant is just pouring out the weep hole.

[Doug Spingelt]

I don't know what the weep hole is.  I assume that is around the water pump gasket?  Isn't the water pump on the front of the engine?  my concern is that it seems further back, but wouldn't suprize me if it were the water pump.  Is that something I reasonably adept person could do themselves?  I recently replaced the fuel pump.

there were no other symptoms, and in fact the engine runs fine still if I start it.  On the hyway, I smelled it first and then was driving and noticed a small stream of water behind me so pulled off freeway, I open the radiator valve and it of course sprayed everywhere.  the engine temp light had not come on yet.  I added a gallon of coolant I keep for emergencies in the trunk and drove about another half mile and then the temp light and buzzer came on and I parked it and had it towed home.  the thermostat is new, so I felt that it was a relaibale measure of overheating. 

I could probably put in a new water pump tonight possibly.  It feels like I would see that leaking from there though, and not mid- engine where I see the water drain, even without pressure.  It must be a gaping hole to run through so fast.  It took about 30 seconds for the water to hit the street from filling the radiator.  It is confusing. 

Thanks as always. 

[Otto Skorzeny]

I can't answer specifically for your car since I've never worked on a fwd Eldo but water pumps are not the most difficult item to replace on a car.

The weep hole is located on the bottom side of the pump shaft housing. When the bearing in the pump wears out, it allows water past the shaft and out the weep hole.

When the water pump failed on a Dodge pickup I owned, water poured out almost as fast as you could put it in.

Remove the belt to the water pump pulley and grasp the pulley with your hands. If the bearing is shot, there will likely be a lot of play when you lift up on the pulley. There shouldn't be any play.

Try this to see where the water is coming from:

Disconnect the top radiator hose at the radiator and leave it connected to the engine.
Slowly add water to the open hose end with a garden hose and try to see where the water first appears.
It may be coming out and running along the block or something making it appear that it's coming from the back of the engine.
Putting the car on ramps will help a lot if you can't see the leak from above.

[Doug Spingelt]

I think i will do that tonight.  the water pump is only $60.00 and I think there is one at the local NAPA store by my work.  I might just replace it as a safety measure anyway.  It would be great if that resolved the issue.

[bcroe]

From your description I'd think its the rear freeze plug; the water pump would be rather obvious and not in such volume.  You certainly will need to pull the motor to fix that & also to fix the manifolds, I'm doing something like that here.     Bruce Roe  CLC # 14630

[Doug Spingelt]

I am slowly comming to that conclusion as well.  I spoke with the NAPA guy here who is pretty knowlegable and is getting to know me and he said the water pump would be notable with the naked eye and that it wouldn't drain out so fast.  Anyway, I think this is a job for a shop.  I was really hoping to drive it this weekend! 

[TJ Hopland]

There are 3 freeze plugs on each side of the block plus a few on the heads and in the back but I dont remember the details on those.  If one is leaking they all could be.  The ones on the drivers side are covered by the transmission and final drive.    This is the best pic I seem to have and I dont have an engine near by at the moment.

[TJ Hopland]

While the motor is out would be a good time for a new timing chain / set and a good look at everything else.  If there is no signs of issues you may not have to pull the heads which will save a few bucks.  The intakes tend to get weepy so I would put a new gasket there.  Pulling the oil pan would be good even if its not leaking.  Its likely full of plastic bits from the timing gear and valve guide seals.  The valve guide seals may be a good reason to pull the heads since its easier to replace them with the heads off the block. 

I had a 425 with a leak that turned out to be the EFE vacuum temp switch.  Its sort of hidden by the distributor.  Also I dont think it could leak as bad as you are describing but who knows its worth a look.  Heres a pic I made for someone else that shows those coolant ports.

[76eldo]

The car has to be diagnosed by seeing where the leak is coming from in person.  It could be anything. 

Brian

[bcroe]

I took a look at a block.  There are no freeze plugs in the front or back of the block, just a cam cover.  There are 3 plugs on each side.  BUT there is a plug in the back of one head, and a heater hose connected to the other head.  If its the heater hose, you'll be back on the road in no time.  Bruce Roe  CLC # 14630

[Ted in Olympia WA]

Just about every Cadillac engine I pull has a leaking freeze plug.  There are only really two places for water to leak; the freeze plug or water pump.

The passenger side plugs can be replace if you take out the starter.  The best way to take them out is to pound them into the block,  Then you can turn them and grab onto them with a pair of visegrips and pull them through the hole.  The best way to replace them with the engine in the car is to get the expandable rubber ones (1 3/4 inch), put a little sealer around them and tighten up the center bolt.

I was going to tell you that it would be impossible to replace the driver's side but after looking at an engine on the shop floor it might be possible.  You sill most like have to disconnect the transmission lines and be able to stand on you head but it might work.  At the very least you should be able to tell if it is leaking or not.  You would need to use the rubber ones here.

The water pump would be leaking on the very bottom through a small hole.  They make them so they do this if the bearing and seal wears out.  The water pump takes labor but it is not that hard the replace.  I think it takes four different size wrenches and the smallest ones you have to be careful not to over tighten.

Everyone will hate me for this but I have fixed freeze plug leaks with heavy duty stop leak and I do not think it is a bad thing.

If anyones ever pulls a engine or puts in a used engine I would always replace all six plugs with brass one before you put them back in.

Good luck.

TED

[Glen]

I vote for a freeze plug. 

The ones on the driver’s side are hard to install but I was able to do it using a pry bar pushing on a socket that was pressing the plug in.  After 10 years of daily driving it is still there.  Getting about time to check them again. 

Glen

[Doug Spingelt]

Thanks a million for the advice!  I got frusterated and took it to the shop.  indeed it was the suspected freeze plug.  they replaces three of them.  the others looked finr still.  they replaced the first two on the drivers side and then the one behind the starter on the passenger side.  The system was preassure tested with 15 lbs of preassure for an hour with no leaks.  that made me happy.  the shop suggested I install a 10 lb preassure radiator cap for good meassure.  (I have q 15 lb one now)  he thought 15 lbs was a bit high for an old motor like this one. 

they were able to do this without removing or fixing the exhaust manifold... unfortunately as I would like that fixed.  oh well.  they are puting a bid together,.

["Cadillac Kid" Greg Surfas 15364]

Doug,
The pressure rating of the cap corresponds to the pressure in the system.  This in turn corresponds to the temperature at which the fluid in the cooling system will boil.
15 pounds relates to a boiling temperature of 250 degrees F (water only). 10 pounds drops it back below 240 degrees.  I don't know about the rest of you guys, but these engines run hot, and 230 degrees running is not uncommon.
What will happen with the lower pressure cap is that when the car heat soaks (stopped after running and warm) the temperature climbs above the running temperature, and if the pressure in the system is too low it will boil over.
I have a hard time imagining a knowledgeable mechanic that would say the older cars should run a lower pressure.
Greg

[Otto Skorzeny]

I've never owned a car that had such a low pressure cap recommendation. The '56 is supposed to be 12 - 15 pounds.

Read your shop manual and install the cap with the correct pressure as called for by GM.

[76eldo]

I agree.

Anything that leaks at 15 PSI needs to be fixed anyway.

By the way, you did the right thing in taking it to a shop and letting them properly diagnose it and pressure test it.

This message board is fantastic, but for something like diagnosing a leak "coming from the engine" it's useless to just guess.

Brian

[Doug Spingelt]

Thanks, and it is leaking again now while sitting in the driveway.  I'll take it back to them next week.  might be a poorly installed freeseplug?  I'll get under it this weekend and see if there is anything to see.  fun.