Problem with cooling system- Can't pinpoint
12-20-2014, 11:26 PM
#1
Problem with cooling system- Can't pinpoint
I've had a small problem with my cooling system for a while now and not really sure where to start. Here's the symptoms:
-Dash gauge shows barely over half way when warm.
-Doesn't appear to be leaking much. I add less than a quart of coolant every couple months. (usually, it's full when I check it).
-I smell a slight coolant smell after driving it, but only from the engine compartment. Can't pinpoint the smell and I see zero signs of leaking.
-Heater doesn't work very well. Blows luke warm.
-I can hear some bubbling/gurgling in the heater core sometimes when cold. No coolant smell inside the cab...no signs of leaks
-No oil in coolant, no coolant in oil, no white smoke from exhaust.
I figured a while back that the problem would get worse and I would be able to figure out what's going on, but it hasn't. I've flushed the coolant system this summer. I plan on putting a thermostat in and possibly even changing the water pump. If I have to, I'll put a radiator in it too, or at least take it out and see if I can test it somehow. I've checked all of the hoses very well and all are in very good shape with no signs of leaks. I know there are some small hoses around the throttle body. I figured maybe one of those had a small leak, but haven't had a chance to check them until recently. I had the tb off the other day (replacing the tps) however, and had a chance to inspect them. No signs of any problems and all hoses look good. I'm leaning toward maybe a pinhole leak in the radiator, but I don't see how that could cause it to overheat slightly. Besides...the dash gauge could easily be off. The system seems to have plenty of pressure, so the pump should be working, I think. Any ideas what could cause this? I'd like to fix it before a bigger problem comes up.
-Dash gauge shows barely over half way when warm.
-Doesn't appear to be leaking much. I add less than a quart of coolant every couple months. (usually, it's full when I check it).
-I smell a slight coolant smell after driving it, but only from the engine compartment. Can't pinpoint the smell and I see zero signs of leaking.
-Heater doesn't work very well. Blows luke warm.
-I can hear some bubbling/gurgling in the heater core sometimes when cold. No coolant smell inside the cab...no signs of leaks
-No oil in coolant, no coolant in oil, no white smoke from exhaust.
I figured a while back that the problem would get worse and I would be able to figure out what's going on, but it hasn't. I've flushed the coolant system this summer. I plan on putting a thermostat in and possibly even changing the water pump. If I have to, I'll put a radiator in it too, or at least take it out and see if I can test it somehow. I've checked all of the hoses very well and all are in very good shape with no signs of leaks. I know there are some small hoses around the throttle body. I figured maybe one of those had a small leak, but haven't had a chance to check them until recently. I had the tb off the other day (replacing the tps) however, and had a chance to inspect them. No signs of any problems and all hoses look good. I'm leaning toward maybe a pinhole leak in the radiator, but I don't see how that could cause it to overheat slightly. Besides...the dash gauge could easily be off. The system seems to have plenty of pressure, so the pump should be working, I think. Any ideas what could cause this? I'd like to fix it before a bigger problem comes up.
12-21-2014, 06:44 AM
#2
1994 F150 XLT 5.8L 2wd
The system has pressure because cold coolant is heated, when liquid is heated it expands, creating pressure. The pump just moves the liquid through the system, it has nothing to do with why the system gets pressurized.
As for no heat that's an obvious blockage in the heater core (either inside with liquid or outside that the air flows through). If you flushed the system this year it may be past the point of being able to be flushed. I would start with heater core (especially if it gets cold where you live) and therm. This will ensure you get heat. If the system is overheating then water pump would be the first item to go then radiator if pump doesn't fix the problem.
Small leaks are a PITA to track, best bet is to examine things right after a drive. I've found wearing a leather work glove is best for detecting leaks, it'll protect you from the heat and shows wetness easily. Just run finger around everything that is clamped and under water pump and therm housing. Don't forget about the petcock on the radiator, those have plastic threads and tend to leak, also the hose that connects to the cold fill reservoir would be another spot that would be hard to visually see a leak.
As for no heat that's an obvious blockage in the heater core (either inside with liquid or outside that the air flows through). If you flushed the system this year it may be past the point of being able to be flushed. I would start with heater core (especially if it gets cold where you live) and therm. This will ensure you get heat. If the system is overheating then water pump would be the first item to go then radiator if pump doesn't fix the problem.
Small leaks are a PITA to track, best bet is to examine things right after a drive. I've found wearing a leather work glove is best for detecting leaks, it'll protect you from the heat and shows wetness easily. Just run finger around everything that is clamped and under water pump and therm housing. Don't forget about the petcock on the radiator, those have plastic threads and tend to leak, also the hose that connects to the cold fill reservoir would be another spot that would be hard to visually see a leak.
12-21-2014, 10:46 AM
#3
The system has pressure because cold coolant is heated, when liquid is heated it expands, creating pressure. The pump just moves the liquid through the system, it has nothing to do with why the system gets pressurized.
As for no heat that's an obvious blockage in the heater core (either inside with liquid or outside that the air flows through). If you flushed the system this year it may be past the point of being able to be flushed. I would start with heater core (especially if it gets cold where you live) and therm. This will ensure you get heat. If the system is overheating then water pump would be the first item to go then radiator if pump doesn't fix the problem.
Small leaks are a PITA to track, best bet is to examine things right after a drive. I've found wearing a leather work glove is best for detecting leaks, it'll protect you from the heat and shows wetness easily. Just run finger around everything that is clamped and under water pump and therm housing. Don't forget about the petcock on the radiator, those have plastic threads and tend to leak, also the hose that connects to the cold fill reservoir would be another spot that would be hard to visually see a leak.
As for no heat that's an obvious blockage in the heater core (either inside with liquid or outside that the air flows through). If you flushed the system this year it may be past the point of being able to be flushed. I would start with heater core (especially if it gets cold where you live) and therm. This will ensure you get heat. If the system is overheating then water pump would be the first item to go then radiator if pump doesn't fix the problem.
Small leaks are a PITA to track, best bet is to examine things right after a drive. I've found wearing a leather work glove is best for detecting leaks, it'll protect you from the heat and shows wetness easily. Just run finger around everything that is clamped and under water pump and therm housing. Don't forget about the petcock on the radiator, those have plastic threads and tend to leak, also the hose that connects to the cold fill reservoir would be another spot that would be hard to visually see a leak.
12-21-2014, 11:05 AM
#4
1994 F150 XLT 5.8L 2wd
If your heater hoses are hot to the touch then you should be getting HOT air, I can't have a hoody and a coat on with the temp on hottest setting and fan on low once the engine is warm regardless of outside temperature.
If they aren't hot then someone may have put a lower temp thermostat in thinking it would help in some way, which seems to be a common misconception- lower operating temp = easier on engine. Not true though, 195 is what the stock therms were and that is the best operating temp for these engines.
To some it up, if the heater hoses are hot and you aren't getting hot air then (assuming your temp selector and blend door are functioning properly) the heater core is the cause. Regardless of the therms set temp running an engine for 20-30 minutes at more than just idle will result in coolant temps hot enough to produce hot air.
As for the gauge reading "a little hot", those things aren't very accurate, only if there is a deviation from where it normally runs would I even consider something running hot. That being said it's not uncommon for the temp sensor to go bad after ~ 20 years.
If they aren't hot then someone may have put a lower temp thermostat in thinking it would help in some way, which seems to be a common misconception- lower operating temp = easier on engine. Not true though, 195 is what the stock therms were and that is the best operating temp for these engines.
To some it up, if the heater hoses are hot and you aren't getting hot air then (assuming your temp selector and blend door are functioning properly) the heater core is the cause. Regardless of the therms set temp running an engine for 20-30 minutes at more than just idle will result in coolant temps hot enough to produce hot air.
As for the gauge reading "a little hot", those things aren't very accurate, only if there is a deviation from where it normally runs would I even consider something running hot. That being said it's not uncommon for the temp sensor to go bad after ~ 20 years.
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broncojunkie (12-21-2014)
12-21-2014, 01:12 PM
#5
Salvage Yard Pro
Thermostat housing. My nemesis! I'd definitely check the housing gasket. Have had 2 do the same exact thing as far as losing coolant and the coolant smell.
12-21-2014, 01:41 PM
#6
Last night, I drove the truck down the road and back. When I got back, I sniffed around the back of the hood and around the sides, where the fender meets the hood. I couldn't smell any coolant. Then, I walked around the front of the truck and smelled the front grill area. I could smell it. I opened the hood and took a flashlight around the radiator, grille, engine compartment, etc. and still couldn't find any signs of leaks. I know it's leaking...I just think it's so small that it's almost impossible to detect.
Maybe after putting in a new thermostat, it will be more noticeable. I won't get a chance to do it until after Christmas, though. We're going out of town.
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12-21-2014, 02:24 PM
#8
Senior Member
My bet for the small leak would be a pinhole leak. I had one on my old 73, and it was a 2 month search. After finding it I noticed that there was some limestone residue beside it. They put that type of gravel everywhere around here. Apparently it hit my radiator just right to cause a superfine crack. The spray was so small though that it would almost evaporate before it touched anything. I used the leather glove method like stated above to find it. Still had to be a hot engine for it to spray. I had to clean the area then I brazed it with some copper alloy to seal it. Worked great until I blew the engine being stupid. Lol.
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broncojunkie (12-22-2014)
12-22-2014, 12:41 AM
#9
12-22-2014, 09:01 AM
#10
Mark
iTrader: (1)
That was one of the first places I looked! And honestly, it does look like there has been a leak there in the past. But I've let this thing warm up and idle while watching it closely. I can't see anything coming out of it.
Last night, I drove the truck down the road and back. When I got back, I sniffed around the back of the hood and around the sides, where the fender meets the hood. I couldn't smell any coolant. Then, I walked around the front of the truck and smelled the front grill area. I could smell it. I opened the hood and took a flashlight around the radiator, grille, engine compartment, etc. and still couldn't find any signs of leaks. I know it's leaking...I just think it's so small that it's almost impossible to detect.
Maybe after putting in a new thermostat, it will be more noticeable. I won't get a chance to do it until after Christmas, though. We're going out of town.
Last night, I drove the truck down the road and back. When I got back, I sniffed around the back of the hood and around the sides, where the fender meets the hood. I couldn't smell any coolant. Then, I walked around the front of the truck and smelled the front grill area. I could smell it. I opened the hood and took a flashlight around the radiator, grille, engine compartment, etc. and still couldn't find any signs of leaks. I know it's leaking...I just think it's so small that it's almost impossible to detect.
Maybe after putting in a new thermostat, it will be more noticeable. I won't get a chance to do it until after Christmas, though. We're going out of town.
The following users liked this post:
broncojunkie (12-23-2014)