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V8 Dakotas
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varnuke
Dodge Dakota
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7/25/2003
18:14:09
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 Subject: 4.7liter Overheating - Case History
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Came here first for solution to my overheating probem, so I thought I'd tell my story too, as it may save someone some money, time and trouble.
2000 Dakota Club Cab 4x4; LSD; Heavy-Duty everything; 4.7 liter with Auto Trans; 164,000 miles [mostly highway - long haul]
Started heating up to 210 on the gauge with the electric fan coming on to help cool down about the end of last summer. Winter came on and the temp acted okay all winter. Spring and Summer this year problem was still there.
Thought it was a sticking thermostat, so I replace it. Still had the problem. Thought I needed a flush, so I did that. Still had the problem. Thought it was the viscous fan clutch, replaced that, still the same. Next thought it was the water pump. Went to replace it and found that the plastic impeller on my pump looked as good as the one on my new pump assembly, which comes with the gasket if you get it from a Dodge dealer.
So, I put the old one back on. Taking the water pump off was very simple. First took off the windshield and radiator coolant overflow tank off by removing the two 8mm screws holding it to the frame, then removed the two electric plugs on the left hand side [looking aft from the front of the truck], and unplugged the hose from the window washer tank and held my finger over the fitting as I lifted the tanks up to the left and then stood it up over the battery and against the hood so I would not have to undo the other hose on the right hand side.
Then I took a large Crescent wrench to the fan nut and smacked it with a hammer a couple of times to loosen it. Came off okay, but first time I did it I had to use a thick rod bent to hook into one of the holes in the pulley on the pump and have someone hold that, pulling in the opposite direction of the way I was hitting the wrench.
Took fan blade with viscous clutch off, then took a 15mm socket with my 1/2" drive breaker bar and turned the Serpentine belt tensioner to the left and took the belt off. Then I removed the idler pulley with a 15mm socket. That exposed the water pump completely. Eight 15mm bolts hold the water pump on, with one on a stud that I had to use a deeper 15mm socket to wratchet off easily.
So, when I got the pump off and saw that the impeller and diffusers were not worn at all even after 164,000 miles, I really started to worry becuase everything I did up to that time covered everything but the radiator, and one more thing I did not consider, which if I had would have saved me a LOT of time and worry.
I had taken out the thermostat a few days ago and made an orifice plate on the lathe to replace the thermostat. Put that in and found that the engine ran really cool as long as I was on the highway, but as soon as I got on the side streets I started to see the temperature climb again. When it got high enough I would put on the heater full bore and high fan to cool it down under 210 again.
Anyway, I put everything back together, including a new thermostat, PUT A NEW SERPENTINE BELT ON, filled it with fresh anti-freeze, bled off the outlet vent just upstream of the coolant fill cap, filled the overflow tank, and took it for a spin.
Temperature held steady all day long. So, what was the problem? It was the belt. The backside of the belt was so smooth as to almost appear like glass. I figure that the belt was slipping on the water pump pulley, decreasing the flow rate completely at slower speeds when the cooling air flow would be way decreased over higher speeds and cooler temperatures, while at the same time the fan would kick in, increasing the torque needed to turn the fan and water pump pulley, which made the belt slip even more than when the viscous clutch would disengage.
So, check the belt first. The new belt backside has a good fresh rubber grip on the water pump pulley. After seeing the plastic impeller, and that there was no degradation or erosion of it at all like metal impellers, I figure that it will last the life of the engine, at least longer than the bearings on the pump shaft.
Sorry for the long post, but anyone can do a water pump if it needs to be replaced because of a bad bearing, but that appears to be all the can go bad from my observation.
I should have changed the belt much earlier, but the truck has not even had a tune up or new plugs and still runs as good as new. All I have done is change the oil [Mobil 1] every 3-4K and change air filters every 15-20K. Don't ask about the brakes, especially the front discs. They should have NEVER outlawed asbestos brake pads, is all I can say. Asbestos brake pads never killed anyone from my perspective, after dealing with steam pipe lagging for over four years in the frigate engineroom back in the 60's and 70's. The brakes are the only thing that has plagued my truck from day one, otherwise it has been a very dependable vehicle. Next one for me will be a 3500 RAM Cummins HO; 6spd. Payload is too wimpy now, but the overall size of the Dakota is great when driving through LA, Chicago, etc. Oh, and Mobil 1 gear lube in the LSD stopped my back tires from cupping wear.
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varnuke
Dodge Dakota
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7/25/2003
20:56:51
| RE: 4.7liter Overheating - Case History
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Correction on the tensioner relief direction. I re-read my post after posting it, and I think now, without looking at the engine, that the tensioner is pulled to the right instead of where I said the left. Yes, it has to be to the right or I would have been going in the counter clockwise direction on the tensioner 15mm nut which would be loosening it. So, you swing your wrench handle to the right to take the tension off the belt. Sorry about that!
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.alex.
Dodge Dakota
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7/28/2003
10:37:12
| RE: 4.7liter Overheating - Case History
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Good write-up. That's correct... tensioner swings right, returns left.
If the factory belt lasted 164,000 then that's pretty impressive in the 1st place.
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BigBlue QC
GenIII
7/28/2003
12:25:01
| RE: 4.7liter Overheating - Case History
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the factory belt is supposed to have a service life of 80000-100000 miles.
2002 QC 4x4 Sport Plus, 4.7L, auto, Patriot Blue, Tire & Handling group,
Heavy Duty Service group, Leer cap w/out windows, Mopar Step bars and roof rack, Rhino liner in bed and on step bars, Pace Edwards Power Tailgate lock
3.55 rear, 4-wheel anti-lock brakes, all possible fluids are AMSOIL
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Olle Ronn
Dodge Dakota
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9/07/2003
21:26:21
| RE: 4.7liter Overheating - Case History
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Since I am buying a 2003 Dodge Dakota 4x4 4.7 liter V8 truck, I like this kind of input.
Keep it coming. Is the 4.7 liter 318 cu.in.?
Thanks,
Olle
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287ish
Dodge Dakota
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9/07/2003
21:37:13
| RE: 4.7liter Overheating - Case History
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287ish
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Deno24
Dodge Dakota
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9/07/2003
23:16:12
| RE: 4.7liter Overheating - Case History
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Running lower airpreasure in the rear tires will also stop the cupping. Say 28-32 lbs
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Jay Stern
Dodge Dakota
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10/01/2003
15:20:06
| RE: 4.7liter Overheating - Case History
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Comprehensive post. Makes me question the problem I think I have. It's an '87 Dakota that was run into the ground by various employees: Little things like dumping sand in the radiator. The employees are gone but I still have the truck. Anyhow, the engine has about 167,000 miles on it. Power has gone from so-so to pretty bad. No oil leaks, but the oil pressure starts at about mid-range, then goes to zero when accelerating. It rises when the throttle is released. It can idle forever, but in normal driving, the temperature appears to go hot very quickly. Yet, no coolant appears lost and the temperature came down quickly on parking and idling for a few minutes. I suspected a bad oil pump, but aftr reading the posts here, I wonder. Any thoughts? (By the way, the sand was eliminated by new radiator, flushing and replacing the freeze plugs. The sand next to them caused them to corrode away; no coolant circulation. If I ever find the guy.....)
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varnuke
Dodge Dakota
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10/01/2003
20:38:49
| RE: 4.7liter Overheating - Case History
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Correction to first post: Those two screws holding the window washer tank and radiator overflow tank are 10mm.
Follow up to first post above:
After not replacing the water pump, the truck ran okay without any noticeable overheating tendencies for about a month or so. Then it started again. I was thinking that I had a head gasket leak, but when it starts there is no white smoke, it idles okay, and there is no noticeable decrease in the overflow tank level, so I figure the head gasket is okay.
I went back to the dealer and picked up the new pump again. They still had it in stock. When running at speed on the highway there is no problem at all with the cooling temperature remaining steady about 1/8" to 1/4" down from the 210 tick on the temp gauge. When I pull a hill or come to a stop and idle for a while, it starts to heat up to 210 again and the auxiliary fan comes on.
I was thinking that the only thing left is the pump and maybe the belt tensioner. I figured that the pulley on the pump, since it was completely polished down to the metal, tells of belt slipping because of something. Like I said, the impeller was as good as new. So, what is causing the overheating problem when the radiator was flushed and works fine, the thermostat was replaced twice and works fine in a hot pan of water on the stove, the fan clutch is new and works as well as the old one, the system is vented at the top where the top vent hex screw is located just upstream of the radiator fill cap, and the fan belt is new?
When I got the pump off this time I spent more time inspecting it and found that when I spun it as fast as I could by hand I could sense some play in the shaft, indicating that the bearings are not as good as they should be as far as play is concerned, and I could "hear" the play in the shaft housing. So I replaced the pump with the new one. Figured that this should solve the problem for good now.
Well, it still has a tendency to heat up but not always. It is getting cooler now, so it is not as likely to heat up as much as before with the outside air temp going down. But I did notice it do the same thing as before at least once since replacing the old pump with the new one.
The only thing I have left that has not been done is to replace the belt tensioner, which I have not looked at yet as far as difficulty is concerned. Should be a simple thing I'd think. It is the only thing left that I can think of that may be causing the problem.
There is plenty of flow and cooling when at speed, but only when in stop and go traffic or stopped does it start to heat up. The radiator does not have too many bugs in it and is clear, the fan clutch works, the thermostat works, the pump works, there is enough fluid, and there are no detectable leaks in the system, it's clean.
I'm going to watch the black paint on the new pump pulley to see if it starts wearing off. If that is the case, then it has to be the belt tensioner because that is all that is left when it comes to driving the system to keep the pump impeller rotating.
Anything else I am overlooking that you are aware of, please let me know. I can take that pump off and a new one on in less than an hour now.
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Allan
Dodge Dakota
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10/02/2003
09:00:52
| RE: 4.7liter Overheating - Case History
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Is it still the original radiator? I can't believe that the radiator is still perfect after so many miles. Anytime that the temperature is okay at speed but climbs when idling would indicate that the radiator is blocked. It doesn't take much blockage for the temperature to rise. Just my thoughts.
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Kowalski
Dodge Dakota
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10/02/2003
15:10:59
| RE: 4.7liter Overheating - Case History
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Respectfully, I must disagree. That situation would more likely be something like a slipping belt. Idling, the fan moves the air; at speed, its your speed that moves the air. A partially blocked radiator would overheat either way.
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Jay Stern
Dodge Dakota
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10/02/2003
15:39:04
| RE: 4.7liter Overheating - Case History
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In my case, I looked at the fan belt and it looks just fine. Thing is, why should the oil pressure go to zero accompanied by loss of power and indicated high temperature? No coolant loss, no oil loss. The radiator externals look fine; no bugs, etc., plugging it. There is a radiator in front of the main. Is that for the transmission or the air conditioner? I don't know.
-- Jay
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Kowalski
Dodge Dakota
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10/02/2003
16:13:48
| RE: 4.7liter Overheating - Case History
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Sorry if I confused you Jay, that response was to Allan's claim. I have both components in front of my radiator, you could trace the lines to see. You could easily have a serious oiling problem - the extra friction would rob power and create heat.
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Jay Stern
Dodge Dakota
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10/02/2003
19:05:27
| RE: 4.7liter Overheating - Case History
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Kowalski wrote: "Sorry if I confused you Jay, that response was to Allan's claim. I have both components in front of my radiator, you could trace the lines to see. You could easily have a serious oiling problem - the extra friction would rob power and create heat."
Thanks, but I did understood your note was a response to Allan. On our Dakota, I think the problem is the oil pump. To check appears to require removing the engine, or at least lifting it 4 inches. That's a lot of work. If it is something else, it would be nice to find out! Thing is, if lack of oil is the problem, I think I'd smell burning, see smoke rising from the filler opening, etc. There is nothing like that.
-- Jay
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Dally
Dodge Dakota
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10/02/2003
19:58:55
| RE: 4.7liter Overheating - Case History
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I do believe that I have had this peoblem before, and I went through all of the B.S. that Varnuke went through. Only to reluctantly change the rad at my (old and wise) fathers 200th "I told you" request. and VOILLA, Done Deal !! Sometimes the thing that you don't want to believe, is exactly what it is that needs to be done.
A rad with 15% of the cores plugged internally, can't always be detected without actually rodding the rad through at a rad shop.
I also learned that when aluminim and antifreeze age togather, there is an acid that develops, this acid causes corrosion, and this corrosion flakes off of the base material, plugging up your rad. This same acid also eats your head gasgets. GET YOUR SYSTEM FLUSHED EVERY 2 YEARS AND ADD AN ACID NEUTERALIZER.
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Kindig
Dodge Dakota
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10/03/2003
00:11:56
| RE: 4.7liter Overheating - Case History
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Varnuke, I worked in the engine room for 4 years also, I was an MM3 on the USS COOK DE-1083 and the USS Piedmont AD-17.
I can remember seeing asbestos floating in the air in the engine room. We took in all that crap for 4 years. BTW my Lungs are clear. GO figure
Late,
Mark Kedik USN 71-75 Vietnam Vet
2001 Dak 4x4 slt auto 3.55 gears and heavy duty everything
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Allan
Dodge Dakota
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10/03/2003
08:26:57
| RE: 4.7liter Overheating - Case History
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I had a 95 GT Mustang that had a partially blocked radiator. It was fine running down the road but when ever I stopped , traffic lights, stop and go traffic, the temp. would rise. It may have only been blocked a bit but that was enough to raise the temp. Thse days with alum. radiators and plastic end sections they don't rod them out as they could poke the rod through the alum tubes. Better just to pay for a new radiator. They will put your old plastic end sections on the new radiator. And with the sort of mileage that I believe that Varnuke had (164,000) on it then I think he did well on it lasting that long. Regular flushing will certainly give you longer life but eventually it will block up.
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varnuke
Dodge Dakota
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10/03/2003
10:05:07
| RE: 4.7liter Overheating - Case History
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Kindig, yep, me too. MM1. Spent 4yrs and 2 mos on board USS Truxtun DLG(N)-35 from '69-'73 in #1ER & RX off the coast of Haiphong for 1yr 7 mos.
Breathed in a whole lot of asbestos dust over those four years from the steam pipe lagging, not to mention the ear splitting sound from the SLOP on the main engine. Lungs still okay today as far as I know, but ears are not too good. Nobody ever said anything about the asbestos or noise back then. We were expendable, just like everyone is over in Iraq today, with nothing to do with national security I might add - in my opinion.
They should have never gotten rid of asbestos brake pads. Those new ceramic pads warped my Dakota discs continually. Had them replaced six or seven times during the warranty period. I think the brakes are too small for the truck. Asbestos was the best for brake shoes.
I have over 172,000 on my 2000 4x4 now. The radiator is the only thing I have not changed thus far. I checked it out as much as possible and flushed it twice, but it could be the culprit. There was absolutely no crud in the system when I first drained it, nor could I see any residue anywhere in the system internals. I've never had a radiator on any of my cars go bad after such relatively low mileage. Every car I have ever owned I have run for 150-200K miles with no radiator problems whatsoever, and this Dakota is the first vehicle I ever flushed in my life. Maybe flusing it screwed it up? Just kidding.
Right now it seems to be working fine with the drop in temperatures outside. I just might go with it through the winter the way it is and keep an eye on it to see if anything changes. For sure it is either heat removal problem which is a function of "U" and the heat transfer area on the radiator due to blockage (remember: Q=UA[T2-T1]) and/or flow rate out of the pump.
Have not looked at how hard it is to remove and replace the radiator. Wondering if you have to breach the AC condenser connection to remove the radiator, or if you can get the radiator out easily enough without having to remove too many other things to get to it? If not, I could change out the radiator easily enough this coming Spring.
In the meantime, I am going to watch the black paint on the new water pump pulley to see if it wears off prematurely. I tend to think that my belt tensioner may have lost some of its spring tension, but how much I don't know. I have to check on that to see what can be replaced - like the spring alone or the whole assembly.
It probably would have been good if they designed it so that the Serpentine belt had ribs on the backside too that engaged the water pump pulley. A little more surface area contact might have been better considering it has to run that fan sooner or later.
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Jay Stern
Dodge Dakota
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10/03/2003
12:01:09
| RE: 4.7liter Overheating - Case History
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O.K. I understand what you guys are saying about a plugged radiator -- or even slightly plugged. If the thermocouple is located in a place where circulation is poor, you can probably see a false elevated temperature. But what about the oil pressure dropping to zero on the gauge? I don't know if the pressure is mechanical or electronic; i.e. -- a bourdon tube or pressure cell. If a tube, it could be plugged. Except that I wouldn't expect to see a pressure reading at startup, only to have it drop to zero after driving for a while. And, there is that loss of power issue. I keep thinking it is the oil pump. Any comment?
To you ex-Navy guys: Asbestos inhalation can cause mesotheolima, a cancer of the lining of the lungs. However, I've only heard of it -- read case studies -- where the patients were also cigarette smokers. The mechanism is said to be due to the asbestos particles "lancing" the individual cells which causes damage. The repair by the body gives opportunity for new cells to grow that may be subject to mutation. These cells can proliferate and are defined as cancer. The idea is that once inhaled, asbestos fibers remain in the lungs. They apparently do not become encapsulated and remain as irritants to the cells, damaging them, and prompting the body to initiate repair. In theory, of course, any dividing cells can become cancerous because of the opportunity for mutation. Candidly, for the fellows who were exposed to asbestos in boiler rooms, etc., you should have regular chest X-rays as well as having your lung capacity tested. And, if you smoke, well, I don't know. It may be too late anyhow.....
-- Jay
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Yup
Dodge Dakota
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10/03/2003
19:25:57
| RE: 4.7liter Overheating - Case History
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Junk it.
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Marsh
Dodge Dakota
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10/04/2003
01:52:58
| RE: 4.7liter Overheating - Case History
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I have a 2000 Dakota 4.7L auto with about 60K miles. I have had the overheating problem for the past six months (summer). It overheats in slow traffic, sitting at an idel, mostly with the AC on. I too have replaced the thermostat, fan clutch, and put a two row radiator into the vehicle. The new radiator seemed to solve the problem for about three weeks, and it is now doing the same thing. I will try scuffing up the belt.
I am now 58 and when I was in my 20's worked on VW's. Part of the service was to stick the air chuck into the brake drum inspection hole and while applying air spin the tire. This would create a large black cloud of asbestos dust, which I inhaled day after day. So far haven't suffered any ill effects.
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