overheating problem with engine swap
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Intermediate
Joined: Nov 2014
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overheating problem with engine swap
So I have a 1979 L48 I just swapped in a brand new 383 stroker every thing on the engine and the engine cooling is new OEM radiator fan shroud fan and fan clutch the water pump is new everything on the motor for the exception of the alternator is new ..
So I fill the radiator run it then check it fill her up again drive it for about forty miles then the temp skyrockets from 180 to 280 in a heart beat I watch it rise so I take the car home let it cool check it again the tank is half empty so I figured there was an air pocket I fill it up again this time trying to burp the system to get all the air out I even ran it while filling so the water was moving through the system.....ran it again this time it made it about 80 miles on the freeway doing 60mph no roughness just easy cruising the temp was steady at 180 then wam instantly 280 I had to pukk off the freeway and repeat the refill and burp at a gas station
Can anyone help here my father suggested it could be that my transmission is keeping the rpms high which is overheating the motor..I'm not so sure I'm using the original th350 with original torque converter.... Also another theory is that the original size radiator (double core) isn't big enough for the motor
Any suggestions would be great
So I fill the radiator run it then check it fill her up again drive it for about forty miles then the temp skyrockets from 180 to 280 in a heart beat I watch it rise so I take the car home let it cool check it again the tank is half empty so I figured there was an air pocket I fill it up again this time trying to burp the system to get all the air out I even ran it while filling so the water was moving through the system.....ran it again this time it made it about 80 miles on the freeway doing 60mph no roughness just easy cruising the temp was steady at 180 then wam instantly 280 I had to pukk off the freeway and repeat the refill and burp at a gas station
Can anyone help here my father suggested it could be that my transmission is keeping the rpms high which is overheating the motor..I'm not so sure I'm using the original th350 with original torque converter.... Also another theory is that the original size radiator (double core) isn't big enough for the motor
Any suggestions would be great
Melting Slicks
Joined: Jul 2006
Posts: 2,291
Likes: 492
From: Salmon Arm, BC
-The first thing i would try is a new thermostat. If it works fine for some time then all of a sudden doesn't something could be wrong with it. Test the new one in a pot of water prior to installation as well.
-Just confirm that the lower air dam is installed ( it forces air up into the radiator area)
- Another thing that can cause this is a lower radiator hose collapse, this essentially blocks flow of water to the engine. If the rad is restricted at all this could happen ( I'm not sure if you put in a new rad or not.)
-
-Just confirm that the lower air dam is installed ( it forces air up into the radiator area)
- Another thing that can cause this is a lower radiator hose collapse, this essentially blocks flow of water to the engine. If the rad is restricted at all this could happen ( I'm not sure if you put in a new rad or not.)
-
Melting Slicks
Joined: Jul 2006
Posts: 2,291
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From: Salmon Arm, BC
Thread Starter
Intermediate
Joined: Nov 2014
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ok so at the start of the trip with new motor and everything else under the hood the thermostat was new and tested....I stopped once due to overheat due to what was thought over rpm with the transmission maintaining 70mph after about 40 miles...so I cooled the engine got back on the road after another 40 miles it over heated again found out due to an air pocket so I cooled the engine refilled the radiator it aver headed again so I stopped at a friends house and replaced the thermostat with a heavy duty one from orielys and a new radiator cap filled the radiator up again this time burping the system trying to get the air out this time it lasted about 70 miles before overheating (keep in mind it maintains 180 degrees then in the span of a minute after 40-70 miles overheats) so I made it home after burping an c refilling the radiator at ever gas station between LA and san diego and I have no Idea what the problem could be
Melting Slicks
Joined: Jul 2006
Posts: 2,291
Likes: 492
From: Salmon Arm, BC
I'm thinking it's the lower rad hose collapsing, which cuts off the cooling supply, causing the instant overheat.
Time to tiewrap your video camera to something in the engine compartment pointing at the lower rad hose ( rig up a 12V light if you have to) and go for a drive.....that might shed some light on whats going on.
Take some water with you this time.....
Time to tiewrap your video camera to something in the engine compartment pointing at the lower rad hose ( rig up a 12V light if you have to) and go for a drive.....that might shed some light on whats going on.
Take some water with you this time.....
Thread Starter
Intermediate
Joined: Nov 2014
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I'm thinking it's the lower rad hose collapsing, which cuts off the cooling supply, causing the instant overheat.
Time to tiewrap your video camera to something in the engine compartment pointing at the lower rad hose ( rig up a 12V light if you have to) and go for a drive.....that might shed some light on whats going on.
Take some water with you this time.....
Time to tiewrap your video camera to something in the engine compartment pointing at the lower rad hose ( rig up a 12V light if you have to) and go for a drive.....that might shed some light on whats going on.
Take some water with you this time.....
Melting Slicks
Joined: Feb 2006
Posts: 3,105
Likes: 96
From: Sunrise FL
Timing retarded?...distributor mech advance working?? initial set right? Vacuum advance hooked up???
You are correct to keep rad full, keep checking
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Melting Slicks
Joined: Oct 2012
Posts: 2,156
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From: Dunedin NZ.
Sounds serious, you have a "kettle" for an engine. I assume the water is being blown out of the radiator overflow? Do you have a catch tank/overflow tank? Is this being filled up when the overheating takes place? The dash temp gauge is not always accurate, I suspect that the temp is higher than the indicated 180 deg and then it boils shown by the gauge jumping to 280 deg. Check timing as Mikem suggested,also bottom hose as sstocker mentioned, but could also be a head gasket leaking when the engine is hot pressurising the coolant system forcing out the water. i had an engine once (not GM) that consistently ran hot, turned out the crank had a slight bend in it:-(
Thread Starter
Intermediate
Joined: Nov 2014
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So I checked the oil and as an option I cutoff the vacume advance for the distributer it was connected .....I unconnected it to play with timing but it had no affect so I reconnected it as far as the other stuff I'm a beginning mechanic lol so I'm still a little ignorant to things
Burning Brakes
Joined: Aug 2011
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Most important question is where does the water keep going? is it puking out the overflow tube IE a bad head gasket? And by water I presume you mean a 50 50 mix of water and anti freeze? Even pressurized water will evaporate.
Instructor
Joined: Dec 2011
Posts: 189
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From: Virginia
[quote] I had up to six gallons of water in the vette with me lol [quote]
I assume when you say that you are adding 'water' that you are also adding some type of anti-freeze mixture.
The AIM has a note on how the radiator was filled at the factory:
Disconnect the upper radiator hose from the thermostat housing. Hold the upper radiator inlet hose vertical and install additional coolant thru the upper radiator hose until overflow occurs at the intake manifold of the thermostat housing. Then connect the upper hose to thermostat housing.
Hopefully that should eliminate any air pockets in the cooling system.
I assume when you say that you are adding 'water' that you are also adding some type of anti-freeze mixture.
The AIM has a note on how the radiator was filled at the factory:
Disconnect the upper radiator hose from the thermostat housing. Hold the upper radiator inlet hose vertical and install additional coolant thru the upper radiator hose until overflow occurs at the intake manifold of the thermostat housing. Then connect the upper hose to thermostat housing.
Hopefully that should eliminate any air pockets in the cooling system.
Drifting
Joined: Jun 2012
Posts: 1,990
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From: Port St. Lucie Fl
If it were the head gasket wouldn't it be smoking from the intake stroke sucking in coolant? Air pockets wouldn't take 80 miles to make the car over heat, check passenger side floor board for wet carpet. Leaking heater core or hoses could cause it to drain out and run out of coolant over a long drive.
Melting Slicks
Joined: Jul 2006
Posts: 2,291
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From: Salmon Arm, BC
Don't worry about mixing with the antifreeze yet, fix your problem, then drain some water out and add the antifreeze later. You need antifreeze to prevent the block from rusting, and to provide lubrication to the waterpump....as well as the obvious preventing freeze ups.
Were assuming the water isn't ending up in the oilpan.......right
Were assuming the water isn't ending up in the oilpan.......right
Last edited by OMF; May 11, 2015 at 06:52 PM.
Racer
Joined: Mar 2013
Posts: 298
Likes: 2
From: Orange Park Florida
You may need to reject the carb for a 383. It maybe leaning out and that would cause overheating. Also the cam your using may make less vacuum and cause less vacuum advance and that can cause overheating. You may have both Sanrio going at that same time. This happened to me.
Thread Starter
Intermediate
Joined: Nov 2014
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ok to answer everyone's questions the engine is a re-manfactured 383 stroker long block from raptorengines.com the old water pump was replaced with a new one on installation of the motor the problem had be diagnosed as a blown head gasket the exhaust is white and smells sweet which is a big indicator as well as the overheating as to where the coolant is going i assume when it over heats its pushed out through the coolant overflow while boiling ive seen it happen once so thats the current assumption also i believe the blown gasket might be due to a lack of following builder instructions the say after the first start up im to retorque the head bolts which we never did also there may be some timing and tuning issues to work out as well but thats update i need to get a torque wrench and see if tightening the the head bolts could alleviate this issue