Help! 79 L82 Cooling Issue

[Johnw222]

I am really lost at this point as well as several others around me in finding the fix for my 79 L82. My top radiator hose continues to build so much pressure that it adventually blows of! Now let me tell you what I have replaced or went over. I am on my third radiator (2 New ones), I have replaced the thermostat 3 times drilled a small hole in one, ran without a thermostat, replaced the water pump, replaced the hoses upper and lower and transmission cooling lines, replaced the cap 3 times to include a pressure relief cap, replaced the hosing to the overfill bottle, replaced the overfill bottle cap ran without the overfill cap. At first the top hose was completely compressing shut and literally sucking it off of the radiator. Now the pressure builds so much that it blows off. I tried to fill the top hose with antifreeze and/or water to rid of any air pockets in the block, I flushed the system with and without the water pump on. The temp is not exceeding 185 either on my dash instrumentation nor a measured temp from the radiator fluid.

I am exhausted. Please help if you can.

John

 

[73shark]

Welcome to the CAC.

I thought about this and couldn't think of anything that you haven't already tried. I'm guessing that the bottom hose doesn't have any problems.

Someone here will probably be able to give you some suggestions.

 

[GerryLP]

John,

Let's back up a little bit.

First, I am curious how the engine operated and drove a month before you started experiencing these problems

Second, how was the engine operating and driving at the time that you drove it before you noticed the problem. It can be as far two or 3 times before the problem was noticed

for both, tell us about any weird happenings with Vette around both time periods above

GerryLP :cool

 

[Rodney Gold]

Are you sure your heads / head gaskets are ok cos that would be a prime suspect if your cooling system was pressurising so badly it blows hoses off...
You might have an issue there without seeing a water/oil mix.

 

[bill81vette]

Are you sure your heads / head gaskets are ok cos that would be a prime suspect if your cooling system was pressurising so badly it blows hoses off...
You might have an issue there without seeing a water/oil mix.

this sound like the most plausible,especially with the pressure build up in the Radiator,
check your oil,what does it look like???
you took the t-stat out and it still builds pressure?????

and welcome to CAC!!!!!!

 

[KANE]

I agree with the other posts. I too think you have pressure getting past the cylinder heads and into the coolant system.

 

[6880 Mike]

Bad hose clamp?

 

[gmjunkie]

My top radiator hose continues to build so much pressure that it adventually blows of! Now let me tell you what I have replaced or went over. I am on my third radiator (2 New ones), I have replaced the thermostat 3 times drilled a small hole in one, ran without a thermostat, replaced the water pump,

Please allow me to ask a Stupid question,Have you the right Water Pump on the old girl??? Yes there is a Rt hand and Lt hand Water pump!!
Serpentine and some Marine applications pump the opposite direction!!
It's happened to me before,Right Box,Wrong Pump!!
They'll "Damn Sure" get hot and blow hoses off!!

 

[GerryLP]

Are you sure your heads / head gaskets are ok cos that would be a prime suspect if your cooling system was pressurising so badly it blows hoses off...
You might have an issue there without seeing a water/oil mix.

Rodney,

I considered the posiblity as well, and so your post shows we're having similar thinking on this problem, but I have never seen no water/oil mixing somewhere. It if its happening, then there should be signs somewhere...:confused

John, given what you mentioned about the several changes in parts and fluid, I doubt that the engine has been run long enough to show signs of oil in the cooling mixture. Instead, it would perhaps be more fruitful to search for water in the oil system as Billy suggested (and Rodney implied ).

Junky, insteresting on the pump issue. I never thought about it, and some thing new learned. Then I again, I have not messed with LS1's or LT1's for that matter, so when I do, I'll remember that. I have been tempted to put a reverse flow system in the L81, but nah, I like my L81 the way it is. :L Thanks for the tip!

GerryLP:cool

 

[Johnw222]

It was operating fine I did not test it with any enduring driving, we did have the hottest summer ever her in South Texas, it all started with my original radiator blowing out.

 

[Johnw222]

Also the original water pump did it as well that is why I replaced it. I have throughly looked at the head issue. There are no traces whatsoever of any fluid in the oil nor vice versa. The flow through the radiator with the cap off is clean with no air bubbles. The clamps have been replaced several times as I have over-tightened them, thus stripping them.

When I was flushing the block I noticed that there was a greater flow coming out of the right side vs that of the left, I was thinking this might be a possible blockage, but like I said when running cool the fluid is moving with ease through the radiator (viewing with the cap off)

 

[n8dogg]

john
I hate to tell you this but pull the heads and have them checked. I have had this problem with a sbc before. spent weeks trying to chase it down. it came down to a head gasket that would let compression out into the cooling system but not let the water back in. See if you have any heat coming out of the heater core when it is running if not you will have to pull the heads on it.

 

[gmjunkie]

Rodney,

Junky, insteresting on the pump issue. I never thought about it, and some thing new learned. Then I again, I have not messed with LS1's or LT1's for that matter, so when I do, I'll remember that. I have been tempted to put a reverse flow system in the L81, but nah, I like my L81 the way it is. :L Thanks for the tip!

GerryLP:cool

Oh,they have had Lt handed water pumps way back in the Late 60's! Some boats have Twin SB or BB Chevy engines,1 runs Clockwise,1 runs Counter Clockwise! Counter acts the Prop Yaw and makes it easier to hold the going striate on coarse!

Different Ground Cam,WP,Oil Pump,Distributer Gear and Starter,Then a SB or BB Chevy will run in reverse!!
On some of the real old boats (60's to early 80's)they look the identical same on the outside,Just the Impeller in the pump are different!

 

[Johnw222]

john
I hate to tell you this but pull the heads and have them checked. I have had this problem with a sbc before. spent weeks trying to chase it down. it came down to a head gasket that would let compression out into the cooling system but not let the water back in. See if you have any heat coming out of the heater core when it is running if not you will have to pull the heads on it.

Thanks alot guys I will have the heads pulled this week it looks. I will keep you all abreast of the findings to possibly help others out.

John

 

[Rodney Gold]

You get a kit at most parts houses that you put on instead your rad cap and it changes colour if there are combustion gasses , use that before removing the heads..sometimes called a sniffer..take it to a garage that can perform this test if you cant..
If you do remove the heads ,have the heads pressure tested , you dont always see bubbles at idle or oily patches , but what can happen is that when the engine is under load the heads can lift or a crack can open just enough and pressurise the system. no bubbles at idle speeds will not mean that this is not happening.

 

[Johnw222]

You get a kit at most parts houses that you put on instead your rad cap and it changes colour if there are combustion gasses , use that before removing the heads..sometimes called a sniffer..take it to a garage that can perform this test if you cant..
If you do remove the heads ,have the heads pressure tested , you dont always see bubbles at idle or oily patches , but what can happen is that when the engine is under load the heads can lift or a crack can open just enough and pressurise the system. no bubbles at idle speeds will not mean that this is not happening.

Thanks again for the info I will try that in the coming day or so.