Major coolant loss

[cj7jeep81]

First, yes this is a problem with my jeep, but I'm running a 305 out of my '78 chevy in it, so it kinda applies.
I was driving home yesterday, and got about a mile from my house when I saw the temperature rising. Got stopped and popped the hood with the engine running to check to see if I could see anything. No steam coming out and no obvious leaks. After it cooled down, I popped the radiator cap and could not see any coolant, so its very low. I had checked the coolant a week or two ago, and it was right at the top.

When driving, the engine was running perfectly, no power loss or anything. Also didn't notice any white smoke coming out the exhaust. I looked this morning and couldn't feel any leaks from the hoses or anything. I'm going to try replacing the thermostat tonight, but doubt it will help much.

Here's some background. Rebuilt the engine a few years ago, and haven't had any problems. Swapped the engine into my Jeep about 4,000 or 5,000 miles ago. At that time put in a brand new aluminum radiator, new heater core, and new hoses all around. Only issue I know is I don't have an over-flow catch can, and just have a hose hooked up to the overflow that just hangs down out of the way.

I'm going to drain the oil tonight and check to see if there's coolant in it (just changed the oil last weekend, and it was clear then). I'm also going to refill the radiator tonight, and start it up and check for leaks/smoke.

Any ideas on what it could be? I'm hoping its not a blown head gasket, but thought it was really odd that it happened all of a sudden like that. Never had any over heating prior to last night, and coolant level was always full.

 

[resurrected_jimmy]

losing that much coolant you don't really need to change the oil,just pull the dip stick and have a look. If its going into the oil pan you will be able to tell

 

[guz71]

305 heads are kind of known to warp, so i was thinking blown head gasket but you said it never got that hot. Just cause there isnt any coolant in the oil or burning out the exhaust, doesnt mean that the gasket isnt blown or there isnt a leak. Sounds like its loosing water fast, so if its loosing it that and its getting into the oil you should be able to tell by just pulling the dipstick and see if its milky. Could be leaking out the water pump?

 

[4X4HIGH]

Check your passenger side floor board for coolant, could be a leaking heater core.

 

[cj7jeep81]

i'll check aroudn the water pump tonight. anywhere in particular i should look?

shouldn't be the heater core, as its less than a year old, but no, no leaking on the floor board.

 

[Rednekjimmy86]

Yeah, I just had the same problem with my 305 almost identical. I thought for sure I had blown a head gasket, when I took the motor apart the head gasket seal was good but the head was cracked. More then likely it's the heads.

 

[cj7jeep81]

i hope its not the heads. i had them gone over and re-worked a bit (valve job, porting/polishing) when I rebuilt the engine, but who knows. if that's the case, i think I'll just get a crate motor 350. I don't want to use junkyard parts, and I can't justify spending $500-$600 on heads when I can get a crate motor for $1500.

Yeah, I just had the same problem with my 305 almost identical. I thought for sure I had blown a head gasket, when I took the motor apart the head gasket seal was good but the head was cracked. More then likely it's the heads.

 

[blazeonchevy]

When a radiator is full doesnt the fluid go into the overflow when the engine is shut off hot? So if there was just a hose there the coolant would leak out until it got low enough. (too low). Correct me if im wrong. Just a theory..

 

[cj7jeep81]

i had thought about that, but i've had it set up like this for quite a while now (probably going on a year), and i just checked the fluid level a week or two ago and it was full. i haven't had to add any fluid since i first put it all together back then. i would think if this was the problem, it would have gradually done so, not all in a week or so between checking and last night.

When a radiator is full doesnt the fluid go into the overflow when the engine is shut off hot? So if there was just a hose there the coolant would leak out until it got low enough. (too low). Correct me if im wrong. Just a theory..

 

[vortec]

i hope its not the heads. i had them gone over and re-worked a bit (valve job, porting/polishing) when I rebuilt the engine, but who knows. if that's the case, i think I'll just get a crate motor 350. I don't want to use junkyard parts, and I can't justify spending $500-$600 on heads when I can get a crate motor for $1500.

i'd check the freeze plugs and coolant temp sensor. i've had both leak on engines and at first, it wasn't even leaving the normal crusty trail. plugs are cheap, but a hassle to install without pulling the engine.

if it is the heads, too bad you don't live in texas. i have some 305 HO heads taking up space. . i'm not trying to sell stuff in the garage. that would be naughty of me. just saying...

 

[cj7jeep81]

yeah, and shipping would probably be crazy expensive. plus, this is my daily driver, so while building it I've been avoiding used parts as much as possible (learned my lesson in the past). I'll fill it up with water tonight and let it run and look around for leaks/white smoke. I'll also check the oil.

too bad you don't live in texas. i have some 305 HO heads taking up space.

anyway, some suggestions: freeze plugs and coolant temp sensor. i've had both leak on engines. plugs are cheap, but a hassle to install without pulling the engine.

 

[vortec]

yeah, at 50lbs apiece, it would cost more to ship than i'd ask for the parts. they'd work fine, but i feel the same way about used parts. only new stuff for my dd. sort of ironic, considering the fact that i do much more dangerous stuff with the blazer, and being stranded on the side of a highway is not the same as being upside down in a ravine or something.

 

[cj7jeep81]

yeah, i'm sure they're fine, but you never know what's going to happen. and especially with the time involved in swapping them out, may as well do it once.

guess if it is the heads, it gives me more incentive to get one of my other trucks running. got a '79 k20 that i'm removing a 10" lift from, and almost have it done, but then need to figure out why it doesn't want to start. or, i could scrounge up a new engine and transmission for my '78 stepside, but don't really want to do that right now either.

yeah, at 50lbs apiece, it would cost more to ship than i'd ask for the parts. they'd work fine, but i feel the same way about used parts. only new stuff for my dd. sort of ironic, considering the fact that i do much more dangerous stuff with the blazer, and being stranded on the side of a highway is not the same as being upside down in a ravine or something.

 

[cj7jeep81]

a quick update. found out a few things. first, the thermostat was bad so i replaced it, and found a slight leak at the lower radiator hose. tightened them both up, but still having problems. also found out that it had been 2 weeks since I had checked the coolant level, so my guess is it was slowly leaking over two weeks, and the bad thermostat didn't help.

found a couple of other leaks as well. one leak is on the front outside corner of the passenger cylinder head. it only leaks when the engine is warmed up, but leaks at a decent pace (a drip every few seconds). I've checked the oil, and haven't seen any coolant in there. also no white smoke (once warmed up) out the exhaust or coolant smell at the exhaust. I'm going to pull the valve covers and check torque on all the cylinder head bolts, so maybe I'll get lucky and that will fix it without pulling the heads.

also noticed a drip dead center on the block, right behind the harmonic balancer. I looked but couldn't see where it was coming from, but if I look from underneath I can just see a fairly steady drip dead center there. Granted, I was just crouching in the front looking under it, and tonight I'll climb underneath and see if I can tell where its coming from. Any ideas on where this second leak is coming from?

 

[Thunder]

Your water pump is probabally going bad. When the seal goes it leaks out of a little hole on the WP housing. This hole is directly avove the harmonic balancer and leaks down the center of the engine as you described.
Re torque your heads and replace the water pump.
Check the intake manifopld bolts also. The leak on the head may be the intake manifold gasket leaking out of the corner and running down the head.

 

[cj7jeep81]

Your water pump is probabally going bad. When the seal goes it leaks out of a little hole on the WP housing. This hole is directly avove the harmonic balancer and leaks down the center of the engine as you described.
Re torque your heads and replace the water pump.
Check the intake manifopld bolts also. The leak on the head may be the intake manifold gasket leaking out of the corner and running down the head.

thanks for that! i'm still hoping i can fix this without tearing half the engine apart. I'll try to pull the water pump tonight (while I pull the valve covers). I should be able to see if its leaking, right (at least a discoloration or some sort of mess??), right?

i'm pretty sure the leak is between the head and the block, in the front corner. i can see the water trickeling out, and pretty sure its starting there, but I'll double check.