98 Neon DOHC Over heating - updated
#11
08-26-2008, 08:04 AM
New guy here but I have the same problem with my Mom's 98 neon Sport. (DOHC) Anyway I have a new head gasket kit but really dont wont to pull the head. The reason is when I was pulling the intake off the water port was leaking really bad. My Uncle used stop leak to fix it (if you wont to call that fixing it) and it looked to have stopped the leak. But it would still Overheat. The only thing I could see funny (or not right) was there were small bubbles in the coolant. Other than that it ran great had good power and the oil is clean.
Things replaced
water pump
Rad
and thermostat (which the same uncle cut out)
I have not pulled the head yet and would like not to What is your toughts on the matter. should I just bit the bullet and change the head gasket (cant afford new bolts) or just change the intake gasket.
Things replaced
water pump
Rad
and thermostat (which the same uncle cut out)
I have not pulled the head yet and would like not to What is your toughts on the matter. should I just bit the bullet and change the head gasket (cant afford new bolts) or just change the intake gasket.
#12
11-18-2008, 04:56 PM
Cracked?
I just repaired a 1998 Neon 2.0 with an indentical scenario as yours.
The owner of the car went through the exact same problem, and steps to find the solution.
When the engine was cold, it ran fine, and compression was good, and the leak-down test was perfect (as much as could be expected for a car with 200K miles and running really well!).
When the engine was hot, however, the problem started.
This only took 30 minutes or so to start boiling over. The cylinder head had cracked. When the aluminum was cold, it would seal up almost perfectly. When it was hot, it would swell open and allow combustion pressure and gases to pressurize and fill the cooling system.
After removing the cylinder head and having a machine shop check for cracks, it was verified, and a new head was installed. End of problem.
So when the heat picked up, it would swell open and allow the pressurized gases to leak into the cooling system. The cooling system has all but less than 20 PSI of hydraulic pressure, and the combustion pressure can easily exceed 500 PSI inside the cylinder (this is where the power is developed from combustion) and it doesn't take a genius to figure out that 500 PSI vs 20 PSI, we know where the 500 PSI is headed...
There was no antifreeze in the oil, no coolant in the exhaust, and no white smoke or excess clouds of water trailing out the tailpipe during this diagnosis time.
A check of the antifreeze with an exhaust gas content kit (available at NAPA) will indicate right away that you have a combustion gas leak. If you have a 5-gas available, use it to check, but DO NOT allow the sniffer to go into the water. The water will RUIN the sensing elements.
Just saw this while passing through and thought I might help out.
Have a good day.
The owner of the car went through the exact same problem, and steps to find the solution.
When the engine was cold, it ran fine, and compression was good, and the leak-down test was perfect (as much as could be expected for a car with 200K miles and running really well!).
When the engine was hot, however, the problem started.
This only took 30 minutes or so to start boiling over. The cylinder head had cracked. When the aluminum was cold, it would seal up almost perfectly. When it was hot, it would swell open and allow combustion pressure and gases to pressurize and fill the cooling system.
After removing the cylinder head and having a machine shop check for cracks, it was verified, and a new head was installed. End of problem.
So when the heat picked up, it would swell open and allow the pressurized gases to leak into the cooling system. The cooling system has all but less than 20 PSI of hydraulic pressure, and the combustion pressure can easily exceed 500 PSI inside the cylinder (this is where the power is developed from combustion) and it doesn't take a genius to figure out that 500 PSI vs 20 PSI, we know where the 500 PSI is headed...
There was no antifreeze in the oil, no coolant in the exhaust, and no white smoke or excess clouds of water trailing out the tailpipe during this diagnosis time.
A check of the antifreeze with an exhaust gas content kit (available at NAPA) will indicate right away that you have a combustion gas leak. If you have a 5-gas available, use it to check, but DO NOT allow the sniffer to go into the water. The water will RUIN the sensing elements.
Just saw this while passing through and thought I might help out.
Have a good day.
