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Keep Popping Rad Caps!!!!

StylerG

StylerG

NAXJA Forum User
Location
Oklahoma City
2000 XJ, 99 Engine swap done about 2,000 miles ago. Replaced Radiator, thermostat, water pump and all hoses.
Couple weeks ago, electric fan stopped working overheated on the trail. Noticed that my rad cap was popped allowing pressure to be released. Also noticed there was never a change in my coolant overflow bottle, always the same amount running, not running, hot or cool.
Put a new rad cap on, hard wired the fan wheeled for another day and drove 6 hours home. Went wheeling today stopped to get gas on the way out and noticed that after about 20 minutes of running i was leaking antifreeze, another popped cap.
Any clues as to the fan not working (cts is what i was going to try) and the obvious pressure issues?
With fan hard wired it runs at a steady 210, leaving me to think my thermostat and water pump are working correctly when the fan is working correctly.
 
any other clues on this? After some testing of things that have come up in searches i've found another problem, my upper radiator hose when the engine is warm is easy to press together, and when released i do not feel a "surge" of coolant pass through. It is warmer than my lower rad hose. Also noticed that my coolant reserve tank is about 2 inches over the "fill" line. Put in a new cts last night and air bubbled out in the replacement.... HELP!!!!
 
i just put a 99 engine in maybe 2000 miles ago (2000 "0331" head lasted 220,000 miles...i take care of it) When overheated it went into red but i immediately shut down, i was on a trail. what i mean by popping radiator caps is they pop to release pressure and i have to replace. i.e. pressure releases and coolant flows through cap.

Just got inside from backflushing system, going to replace tstat and possibly water pump...still not getting any pressure or waterflow through my upper radiator hose. During the backflush i squeezed the upper radiator hose and a surge of fluid came out my radiator cap area, took the hose and put it in the radiator cap fill area, disconnected my upper radiator hose and clean water came out of it, so i know there is flow through the radiator. Also took out tstat and ran backflush again to see if tstat was in closed position, no change. Ive driven several hundred miles i wouldnt think my water pump could be bad and i still have an engine that during normal driving could maintain a normal operating temp, but that is only when i have the electric fan constantly on. Mechanical fan is in good working order.
 
StylerG said:
i just put a 99 engine in maybe 2000 miles ago (2000 "0331" head lasted 220,000 miles...i take care of it) When overheated it went into red but i immediately shut down, i was on a trail. what i mean by popping radiator caps is they pop to release pressure and i have to replace. i.e. pressure releases and coolant flows through cap.

Just got inside from backflushing system, going to replace tstat and possibly water pump...still not getting any pressure or waterflow through my upper radiator hose. During the backflush i squeezed the upper radiator hose and a surge of fluid came out my radiator cap area, took the hose and put it in the radiator cap fill area, disconnected my upper radiator hose and clean water came out of it, so i know there is flow through the radiator. Also took out tstat and ran backflush again to see if tstat was in closed position, no change. Ive driven several hundred miles i wouldnt think my water pump could be bad and i still have an engine that during normal driving could maintain a normal operating temp, but that is only when i have the electric fan constantly on. Mechanical fan is in good working order.
Click to expand...

If the cap keeps popping you have too much pressure in the system. The usual cause of this is exhaust gases. Have you done a compression test? At least pull the plugs and check for coolant.
 
i checked for coolant in the oil after it overheated after another days worth of wheeling (had a 6 hour drive home and didnt want to get stuck) and it showed no signs. Im familiar with the signs thats what took my last engine to the scrapper!
 
OK
Finally tracked down the leak to a radiator cap issue...new caps kept losing coolant finally figured out my radiator doesnt seal around the caps and coolant spills out. Going to replace radiator and have been reading threads about which one to get.
Second thing i still cant figure out, twice now ive had a puddle of water/coolant??? under my passenger side front tire, cant for the life of me find out where its coming from. Is this cap related, heater core related or what? No leaks inside cab as typical heater core would go.
Thanks
 
StylerG said:
OK

Second thing i still cant figure out, twice now ive had a puddle of water/coolant??? under my passenger side front tire, cant for the life of me find out where its coming from. Is this cap related, heater core related or what? No leaks inside cab as typical heater core would go.
Thanks
Click to expand...
sounds like a leaking petcock to me. i know its close to there on my '90
 
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