sprocket
Well-Known LVC Member
Hi, I am new to this forum!
I just bought a '96 Diamond Anniversary Mark VIII. I picked up cheap, hoping that it might not have a bad head gasket but it's starting to look like that might be the case.
The engine had been overheated by the previous owner due to a radiator leak. I can tell someone tried stop leak in it. A shop replaced the radiator but it also ended up with a misfire. That turned out to be a loose #6 plug that also had the plug wire boot stuck or melted to the plug. I fixed that.
Then we tried to bleed the cooling system in case the shop had done it wrong (if at all). Right away it took 1 1/2 gallons through the crossover tube. The bleeding from there seemed to go pretty normal as I have done it successfully on my other Mark VIII. I test drove it, staying close to home and the temp gauge stayed rock solid. After 15 minutes I decided to take it on the highway. The gauge stayed steady until I exited the highway, then it suddenly spiked and the heat in the car went from hot to cool. I let it cool down and got it back home with the temp gauge bouncing in the upper normal range.
Since the water pump sounded like it had some bearing noise, we went ahead and changed it and also the thermostat. I used a 180 degree Stant with a wide orifice. Then all hell broke loose!
We absolutely could not bleed the cooling system. The reservoir jug would keep filling up. We noticed that someone had blocked the end of the overflow tube with a bolt, so we removed it. Then it pumped coolant out of that tube and onto the ground. We plugged it back up to avoid the mess. The idle is steady and even but there is some lifter noise. There is no coolant smell from the exhaust. The #6 plug looked like new (which it was) it was not fouled or steam cleaned. There is no misfire, even when first started. After idling for awhile the temp gauge spiked. The circulation you would expect to see looking through the cross tube doesn't seem to be there but it WAS the day before with the first bleed attempt.
I can't think of any explanation other than back pressure from a failed head gasket, and I thought I would come here to see if I could get some suggestions on other checks I can do to confirm it and figure out exactly where the breach is.
Thanks for any help!
I just bought a '96 Diamond Anniversary Mark VIII. I picked up cheap, hoping that it might not have a bad head gasket but it's starting to look like that might be the case.
The engine had been overheated by the previous owner due to a radiator leak. I can tell someone tried stop leak in it. A shop replaced the radiator but it also ended up with a misfire. That turned out to be a loose #6 plug that also had the plug wire boot stuck or melted to the plug. I fixed that.
Then we tried to bleed the cooling system in case the shop had done it wrong (if at all). Right away it took 1 1/2 gallons through the crossover tube. The bleeding from there seemed to go pretty normal as I have done it successfully on my other Mark VIII. I test drove it, staying close to home and the temp gauge stayed rock solid. After 15 minutes I decided to take it on the highway. The gauge stayed steady until I exited the highway, then it suddenly spiked and the heat in the car went from hot to cool. I let it cool down and got it back home with the temp gauge bouncing in the upper normal range.
Since the water pump sounded like it had some bearing noise, we went ahead and changed it and also the thermostat. I used a 180 degree Stant with a wide orifice. Then all hell broke loose!
We absolutely could not bleed the cooling system. The reservoir jug would keep filling up. We noticed that someone had blocked the end of the overflow tube with a bolt, so we removed it. Then it pumped coolant out of that tube and onto the ground. We plugged it back up to avoid the mess. The idle is steady and even but there is some lifter noise. There is no coolant smell from the exhaust. The #6 plug looked like new (which it was) it was not fouled or steam cleaned. There is no misfire, even when first started. After idling for awhile the temp gauge spiked. The circulation you would expect to see looking through the cross tube doesn't seem to be there but it WAS the day before with the first bleed attempt.
I can't think of any explanation other than back pressure from a failed head gasket, and I thought I would come here to see if I could get some suggestions on other checks I can do to confirm it and figure out exactly where the breach is.
Thanks for any help!
