1998 Ram 1500 low temp issue


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Old 03-02-09, 06:04 AM
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1998 Ram 1500 low temp issue

Ok, well it's cold in Green Bay.

However, have a 98 Ram 4X4 (5.9, 164K, 5-spd man) that does not want to get up to op temp. Replaced thermostat yesterday. Water pump replaced a few weeks ago. The top hose (off thermostat) gets warm, both heater core hoses get warm but lower radiator how stay cold or cool. If idled it gets a little warmer. As soon as you start to drive it starts cooling down again. After an hour on the freeway the engine temp is no where near 192. Even running around town at 20mph has a cooling effect on the engine and inside heat feels luke warm at best.

Could it be the 14 deg F air blowing across the engine is keeping it cool enough that the thermostat would not open?
Thanks.
 
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Old 03-02-09, 10:50 AM
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Try blocking the air supply to front of radiator with cardboard or something, see if it comes up to temp.
That will tell you if it's the whether.
 
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Old 03-02-09, 12:24 PM
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Thanks, I'll give that a shot this afternoon. Seems that it might be weather related since that sucker is flat out moving some air! Now I know why the trucks have those grill covers on.

On another note.... I was thinking about replacing the stock fan with an electric one. I've read you should not do such a thing if the radiator is a 4 core. Can you tell by the radiator if its multiple cores? Any words of warning about doing this?

Brian
 
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Old 03-03-09, 05:00 AM
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Ok, I've covered the radiator (left a vertical slot in the middle, about 3 inches) The engine warms up, the radiator warms up but the heater is still cold (at best luke warm).

Should I try to back flush the heater core or bleed the core for a possible air bubble? If I bleed the core does it matter which hose I disconnect?

Thanks.

Brian
 
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Old 03-04-09, 09:21 AM
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Morning all.

So the truck is now getting up to op temp. The heater heats up and blows decent heat, but as soon as you turn the blower up it rapidly cools to almost nothing. I'm guessing it's going to be the heater core. Either it's faulty, clogged or has an air lock issue, correct? Could this also be a vacuum issue, or would that result in no heat at all?

Thanks.
 
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Old 03-04-09, 12:02 PM
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If the thermostat is working then the engine has to get up to operating temperature.
If it is not getting up to temperature then the 2nd thermostat is bad also.
The heater could be a second issue.
Start with the engine alone. Now you are saying that the engine is at operating temperature. Is this determined by the temperature gauge or by "feel"?
You could remove the rad cap and put a thermometer in the coolant and run it and see how hot the coolant gets. Make sure it is a good thermometer for the job.

Just thought of something
Are you gauging engine temperature by feeling heater ?temperature. If that be the case then the engine temperature could be just fine and there is a problem with the heater.
 
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Old 03-04-09, 02:36 PM
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Hey Frankiee, gauging engine (or coolant temp) by the gauge on the dash. I know it's a rough estimate at best. This weekend I'll put a thermometer in the coolant and get a more accurate temp reading. I'm thinking I had a bit of weather related coolness on the radiator which is/was effecting the heater core. I'm thinking my heater core has an unrelated issue because it is capable of blowing "not quite hot" air on the lower fan speeds. The air temp from the register rapidly cools when the blower is turned on high. Yet the hoses feel about the same after the air has turned cool. Again I know touch is not a good measurement, but if the core was being cooled that much that fast I should notice the difference at the discharge hose.

Thanks.
 
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Old 03-05-09, 06:51 AM
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would try flushing out the heater core suspect it may be partially plugged unsure how well you will be able to flush it but suspect you will be able to clean it out enough to atleast notice an improvement.
 
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Old 03-05-09, 08:33 AM
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We are talking a 5.9 gas engine right?
Let me get the facts straight
A couple weeks ago the water pump was changed.
Why was this? To fix the cold heat problem or another reason.?

Did the problem of the no heat and low temp on the gauge start before the pump change or after it.

Yes heat is hard to measure. We do what we can.
 
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Old 03-15-09, 12:14 PM
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Update. Yes this is the 5.9 engine. Water pump was replaced because truck was over-heating. T-stat was also replaced at this time. Coolant flush of radiator and heater core done. Just flushed the heater core again yesterday and let the truck run for quite some time with out a rad cap to release any air bubbles.

Discovered something new. When the RPM's are above 2500 the heater blows hot air. Nice hot air. I've read other posts on various sites about a vacuum check valve (maybe two?) so I'll be replacing both the one off the manifold and the one off the heater core. I don't think I have a vacuum leak though since the system is sucking air when I disconnect one of the vacuum lines. I suppose I'll need to apply the 8 inches of vacuum to see if it holds to be sure though.
 
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Old 03-16-09, 11:42 AM
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I think it is air in the hoses

Truck heater worked fine before the water pump was changed.
System was opened when doing the repair.
I have run in to the odd case of air in system that is hard to get out.
What I do is find the highest heater hose and cut at highest point and put in one of those flush tee connections. The kind you put in to flush out the coolant system.
Bleed it from that point
 
 

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