Cooling System Issue
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Joined: Jan 2020
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From: Pacific Northwest
Cooling System Issue
Truck runs hot, in the upper 3/4 of the temp gauge, but doesn't overheat. I'm out of ideas. Here's the situation:
My kid picked up a 90 B2200 around the first of the year. Runs pretty good except I was having an issue with no heat. Heater controls in the cab all appear to function properly, including the temp selector dial. It's blows warm-ish, but not hot by any stretch. Initially suspected a stuck thermostat; 180° unit tested fine, but replaced it anyway with a new 192° stat. Still no change. Started thinking maybe a plugged heater core, as the heater core intake hose was hot, but the outlet hose was again...warm-ish at best. Pulled the outlet hose and had barely a dribble of coolant coming out of it. Flushed the core and it flowed totally fine. No debris or anything. Put it all back together and figured maybe I'd just have to live with weak heat for a while while I figure this out.
However, a new symptom has recently developed where this truck will run normally in the lower 1/4 range of the temp gauge for a few days, then will unexpectedly start running hot and the gauge will be in the upper 3/4 of the range. It does not overheat, in that it doesn't boil over, but it doesn't cool down until I stop driving and park it. It does not use any coolant. There's no oil in the coolant, there's no coolant in the oil, and I don't see any bubbles coming out of the end of the pickup tube in the overflow tank. I seriously doubt its air locked. I've been driving it this way for a few weeks; I think any air would have worked its way out by now. I don't think the radiator is blocked, as it appears to be a fairly new replacement, and that, coupled with the large, rust colored spray stain on the underside of the hood alludes to the previous owner having cooling issues.
I have a theory, but I think it's a long shot: I'm starting to think the water pump impeller has been compromised, preventing the coolant from being adequately circulated. This could be the cause of the weak stream coming out of the heater core when I pulled the outlet hose off. Is it possible that the impeller has been damaged or corroded to the point it is no longer circulating coolant?
Curious to hear any thoughts or theories.
My kid picked up a 90 B2200 around the first of the year. Runs pretty good except I was having an issue with no heat. Heater controls in the cab all appear to function properly, including the temp selector dial. It's blows warm-ish, but not hot by any stretch. Initially suspected a stuck thermostat; 180° unit tested fine, but replaced it anyway with a new 192° stat. Still no change. Started thinking maybe a plugged heater core, as the heater core intake hose was hot, but the outlet hose was again...warm-ish at best. Pulled the outlet hose and had barely a dribble of coolant coming out of it. Flushed the core and it flowed totally fine. No debris or anything. Put it all back together and figured maybe I'd just have to live with weak heat for a while while I figure this out.
However, a new symptom has recently developed where this truck will run normally in the lower 1/4 range of the temp gauge for a few days, then will unexpectedly start running hot and the gauge will be in the upper 3/4 of the range. It does not overheat, in that it doesn't boil over, but it doesn't cool down until I stop driving and park it. It does not use any coolant. There's no oil in the coolant, there's no coolant in the oil, and I don't see any bubbles coming out of the end of the pickup tube in the overflow tank. I seriously doubt its air locked. I've been driving it this way for a few weeks; I think any air would have worked its way out by now. I don't think the radiator is blocked, as it appears to be a fairly new replacement, and that, coupled with the large, rust colored spray stain on the underside of the hood alludes to the previous owner having cooling issues.
I have a theory, but I think it's a long shot: I'm starting to think the water pump impeller has been compromised, preventing the coolant from being adequately circulated. This could be the cause of the weak stream coming out of the heater core when I pulled the outlet hose off. Is it possible that the impeller has been damaged or corroded to the point it is no longer circulating coolant?
Curious to hear any thoughts or theories.
Junior Member
Joined: Aug 2021
Posts: 8
Likes: 0
From: florida/north carolina
Truck runs hot, in the upper 3/4 of the temp gauge, but doesn't overheat. I'm out of ideas. Here's the situation:
My kid picked up a 90 B2200 around the first of the year. Runs pretty good except I was having an issue with no heat. Heater controls in the cab all appear to function properly, including the temp selector dial. It's blows warm-ish, but not hot by any stretch. Initially suspected a stuck thermostat; 180° unit tested fine, but replaced it anyway with a new 192° stat. Still no change. Started thinking maybe a plugged heater core, as the heater core intake hose was hot, but the outlet hose was again...warm-ish at best. Pulled the outlet hose and had barely a dribble of coolant coming out of it. Flushed the core and it flowed totally fine. No debris or anything. Put it all back together and figured maybe I'd just have to live with weak heat for a while while I figure this out.
However, a new symptom has recently developed where this truck will run normally in the lower 1/4 range of the temp gauge for a few days, then will unexpectedly start running hot and the gauge will be in the upper 3/4 of the range. It does not overheat, in that it doesn't boil over, but it doesn't cool down until I stop driving and park it. It does not use any coolant. There's no oil in the coolant, there's no coolant in the oil, and I don't see any bubbles coming out of the end of the pickup tube in the overflow tank. I seriously doubt its air locked. I've been driving it this way for a few weeks; I think any air would have worked its way out by now. I don't think the radiator is blocked, as it appears to be a fairly new replacement, and that, coupled with the large, rust colored spray stain on the underside of the hood alludes to the previous owner having cooling issues.
I have a theory, but I think it's a long shot: I'm starting to think the water pump impeller has been compromised, preventing the coolant from being adequately circulated. This could be the cause of the weak stream coming out of the heater core when I pulled the outlet hose off. Is it possible that the impeller has been damaged or corroded to the point it is no longer circulating coolant?
Curious to hear any thoughts or theories.
My kid picked up a 90 B2200 around the first of the year. Runs pretty good except I was having an issue with no heat. Heater controls in the cab all appear to function properly, including the temp selector dial. It's blows warm-ish, but not hot by any stretch. Initially suspected a stuck thermostat; 180° unit tested fine, but replaced it anyway with a new 192° stat. Still no change. Started thinking maybe a plugged heater core, as the heater core intake hose was hot, but the outlet hose was again...warm-ish at best. Pulled the outlet hose and had barely a dribble of coolant coming out of it. Flushed the core and it flowed totally fine. No debris or anything. Put it all back together and figured maybe I'd just have to live with weak heat for a while while I figure this out.
However, a new symptom has recently developed where this truck will run normally in the lower 1/4 range of the temp gauge for a few days, then will unexpectedly start running hot and the gauge will be in the upper 3/4 of the range. It does not overheat, in that it doesn't boil over, but it doesn't cool down until I stop driving and park it. It does not use any coolant. There's no oil in the coolant, there's no coolant in the oil, and I don't see any bubbles coming out of the end of the pickup tube in the overflow tank. I seriously doubt its air locked. I've been driving it this way for a few weeks; I think any air would have worked its way out by now. I don't think the radiator is blocked, as it appears to be a fairly new replacement, and that, coupled with the large, rust colored spray stain on the underside of the hood alludes to the previous owner having cooling issues.
I have a theory, but I think it's a long shot: I'm starting to think the water pump impeller has been compromised, preventing the coolant from being adequately circulated. This could be the cause of the weak stream coming out of the heater core when I pulled the outlet hose off. Is it possible that the impeller has been damaged or corroded to the point it is no longer circulating coolant?
Curious to hear any thoughts or theories.
Junior Member
Joined: Aug 2021
Posts: 8
Likes: 0
From: florida/north carolina
oh shoot old post huh... anyway hopefully useful
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