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General Dakota Board
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jb
Dodge Dakota
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8/14/2005
23:04:11
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 Subject: overheating again WTF?????
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Well my 02 Dak 4.7 is overheating again. Last summer it was overheating and blowing all the coolant into the overflow bottle while it was still under ext warranty. The dealer must have had it 10 times trying to fix it. They replaced the fan clutch, t-stat, radiator, water pump, radaitor cap and finally replaced both heads and gaskets. The heads fixed the problem completly for a year.
Now its running hot again even at freeway speeds. I flushed the system, replaced the t-stat again, and the fan clutch. It still runs hot but its not pushing fluid out. I also leaked down the cylinders and tested the anti freeze for combustion gasses. The truck is getting plenty of coolant and flow. Any ideas on what gives??????? I want ot fix it but if i cant get it repaired in the next few days i will be a former dakota owner. This capped off by all the other issued i have had make me think this truck needs to go away but my wallet would like it fixed much better.
btw the truck is a 4wd quad cab and has the max engine cooling package( not working to well apperantly)
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.boB
Dodge Dakota
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8/15/2005
00:21:32
|  RE: overheating again WTF?????
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Bad gauge? Put a temporary mechanical gauge on it.
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SteveJ
Dodge Dakota
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8/15/2005
00:45:43
| RE: overheating again WTF?????
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A coupla possibilities come immediately to mind:
1. You (or the Dodge boys) put an additive in your cooling system that seals coolant leaks.
Never use that stuff. It totally screws up the pressure release and sealing functions of the radiator cap, gunks up the thermostat, and closes down the small coolant passages.
As the pressure cap starts to release to the overflow bottle, or as the thermostat starts to open, the sealer tries to plug those "leaks", and the leak sealer crud slowly accumulates on those parts until they no longer function as designed.
The radiator cap will then eventually get to a point where it won't hold pressure. Now your coolant is always at atmospheric, so it will boil at a much lower temperature than if it were at the 20-21 lbs designed operating pressure.
2. The wrong type or mix of coolant is in your engine. Or tap water was used, instead of distilled.
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From the FSM:
“The use of aluminum cylinder blocks, cylinder heads, and water pumps requires special corrosion protection.
Mopart Antifreeze/Coolant, 5 Year/100,000 Mile Formula (MS-9769), or the equivalent ethylene glycol base coolant with organic corrosion inhibitors (called HOAT, for Hybrid Organic Additive Technology) is recommended.”
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From wjjeeps.com:
"Coolant recommendations and cautions:
The recommended mixture is 50/50 ethylene-glycol and low mineral content water.
Never use pure antifreeze. Only Mopar Antifreeze Coolant, 5 Year/100,000 Mile Formula (glycol base coolant with corrosion inhibitors called HOAT) is recommended. This coolant offers the best engine cooling without corrosion when mixed with 50% distilled water.
Antifreeze mixture must always be at least 44%, all climates year round. Maximum protection (-90d) is provided with a 68% mixture protection. If the percentage is lower than 44 percent, engine parts may be eroded by cavitation, and cooling system components may be severely damaged by corrosion.
CAUTION: Mopar Antifreeze/Coolant, 5 Year/100,000 Mile Formula (MS-9769) may not be mixed with any other type of antifreeze. Mixing of coolants other than specified (non-HOAT or other HOAT), may result in engine damage that may not be covered under the new vehicle warranty, and decreased corrosion protection.
CAUTION: Do not use coolant additives that are claimed to improve engine cooling.
4.7L coolant capacity:
1999-2000: 13.0 qts. (including 2.3 qts. for resevoir)
2001-2004: 14.5 qts. (including 1 qt. for resevoir) "
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When you got the new heads, you got new coolant. The Dodge boys know what coolant goes in your engine, and it's a slim chance they used the wrong stuff. But if there was a blockage building up, perhaps it was flushed out during the head change, but not totally, and now it's building up again.
Did you get to look at the heads they pulled off, to see if there was scum in the cooling passages?
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Red 99 Dak RT
Dodge Dakota
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8/15/2005
08:50:47
| RE: overheating again WTF?????
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Check out this:
http://www.dodgedakota.net/boards/v8/7059.html
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CSzalai
Dodge Dakota
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8/15/2005
15:00:54
| RE: overheating again WTF?????
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Hve you tried changing the radiator.....the bottom end could be plugged. I had that happen on another car i had
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Jb
Dodge Dakota
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8/15/2005
16:03:33
| RE: overheating again WTF?????
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Message:
Thanks guys, I got some more info.
Steve J , I never put anything in the system. The dealer very well could have and i have a feeling they did put some sealer in about a month before the heads were changed because it magically was fine for a month. i told them from day 1 is was a head gasket because of the coolant bottle overflow problem and bubbles in the system, i dont think they wanted to deal with it. The final trip they said it was the radiator cap, i told them they best tail me with a tow truck and order a motor because im hitching up my boat and driveing it till it blows. Then gee an hour later they tell me they found it had a bad gasket and head....
I also just flushed the whole deal, removed the radiaiator and made sure it and the fins werent plugged. I seriouslt doubt its plugged, its less then a year old and has only 15k miles on it.
I never did get a chance to look at the heads. They told me there was a machining defect on the gasket mating surface on the #1 cyl. They were going to only replace the one head but after much b!tching on my part they changed both.
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GeorgeM
Dodge Dakota
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9/03/2005
00:18:38
| RE: overheating again WTF?????
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Message:
Here's a theory for you... You may have had this trouble start for you when you first replaced a water pump. That's what happened to my on my Durango. Overheating ensued. Everything checked out and lots of items were replaced - a very common story with these engines.
I finally diagrammed the system and thought about how it actually works.
If your engine is like mine, there is a bypass hose connecting from the block on the engine side right near the thermostat housing directly to the low side of the water pump, entering from the rear through a special port. The hose is about an inch diameter, and pretty short, about 4 inches total. That's a pretty direct shunt across the water pump output. The radiator has to compete with this for flow, but it's getting its flow through the thermostat.
Cook your thermostat on the stove in boiling water, and chances are you'll see an opening that amounts to less than that bypass hose.
The result is that most of the flow avoids the radiator altogether, with a tremendous impact on cooling capacity.
So why did the problem begin when you changed the pump? You probably took care to trim the bypass hose to fit correctly without buckling. If yours was like mine, the hose was originally buckled in the middle by sloppy installation. I believe that this restricted the flow, and that was important.
The overheating problem disappeared when I put some flow restriction (*not* shut off, however) into the bypass hose, increasing the flow fraction that goes through the radiator when the thermostat is open.
This problem will be very weather sensitive, as this design defect makes the cooling system marginal. It works OK as long as there is some reserve capacity available by further opening the thermostat. If the flow fraction through the radiator is not sufficient when the thermostat is fully open, however (high load or hot weather), any increase in ambient temperature or engine heat output will cause the coolant temperature to rise.
If you decide to try this approach, you'll have to experiment with it. You need significant bypass flow in order to prevent hot spots developing in the engine, and to get good coupling of the thermostat temperature to engine temperature. I used a restriction to about half capacity on that hose. I can't guarantee that this is the correct value.
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