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Discussion Starter · #1 ·
I've replaced the tstat (twice), flushed the coolant, bled the air, replaced the radiator cap, replaced the fan clutch, hosed out the radiator and a/c condenser grills...what else can I do???

It only runs hot while driving in hot (85+) weather. The hotter the weather the hotter it runs, and using the a/c makes it overheat.

I'm thinking my next step is to remove the a/c condenser and really give it a good cleaning (i.e. hose it out backwards), or replace it all together. Is there anything I need to know about removing the a/c lines? Will I need to replace the refrigerant when I'm done? (I have zero experience with a/c systems)

Anything else I should try first?

(2000 Durango, 4x4, 4.7L, no mods)
 

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Licalotapus
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Why remove the condensor to clean it when your engine runs hot?

Does your return hose get real hot when the gauge says it's hot?

If after all that you're still hot, replace the radiator. Parts changing can get expensive.
 

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Hummer Recovery Vehicle
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have you tried replacing the water temp sending unit? how about checking your fuse/relay for your electric fan.
 

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Discussion Starter · #4 ·
The electric a/c fan does work properly (I should have mentioned that in the first place). The engine also starts to boil over when the gauge needle maxes out, so that should indicate the sending unit is working properly as well.

The a/c condenser still has some debris stuck between the fins, so I'm thinking that just enough air flow is being restricted that it only overheats in hot weather. I think I can get it all out if I remove it and hose it out backwards. Removing the condenser would also allow me to inspect the front of the radiator since the condenser covers most of the radiator. I can then decide if either one needs to be replaced.

Now that I think about it, I guess I can just remove the radiator without removing the a/c condenser (true???). This would allow me to inspect the radiator as well as hose out the condenser from the inside.

I have not checked the return hose when the engine is running hot (I assume you mean the a/c hose and not the radiator hose). What does it mean if it is hot?

Thanks!
 

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WORLD'S GREATEST TRUCK
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Mahilly sounds like you need to either go over the stuff you did or get prof. assistance.
It's possible you were given defective eqpt., especially in the fan clutch dept. Search for 'fan clutch', I'm sure you'll find a match. Generally speaking if your needle climbs too high when the vehicle is stopped, it's bad.
You're also aware you need to bleed the system when servicing it?
 

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Loanshark
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Not to state the obvious, but it sounds like you could have a serious problem.

Have you been running distilled water in your system?

There are some places that will clean and test radiators.

If you want a band-aid fix, you could try water-wetter.

Did you test the T-stat before you installed it? I know you've replaced it twice but you never know when your gonna get a bad one.

Do you have one of those nifty after market grills that don't let enough air flow through?

Keep us updated
 

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Discussion Starter · #7 ·
Still not sure what's wrong with it. Yesterday I decided to drive home from work (40 miles) without running the A/C at all... just to see what would happen. It was 97 degrees outside and I was in stop-n-go traffic for the first 40 minutes of my commute. During that time the engine temp stayed right around 210 (or 12 oclock on the dial, which is slightly high, but not bad).

When traffic started moving and I was going 65+ mph that's when the engine temp jumped up to around 230 or 240. For some reason the car only runs hot while driving fast on the freeway. Maybe it's a bad water pump that can't produce enough water flow at higher RPM's????

I don't get it.
 

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WORLD'S GREATEST TRUCK
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there's 19 possible causes in the FSM, you're not losing fluid, right? They also mention dragging brakes. Even incorrect concentration.To check water pump or restriction, NOT WHILE ENGINE IS HOT, remove rad cap, drain level until you can see some fins. warm up engine so stat opens. you should see flow that increases with engine speed.
 

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I would bet on the water pump. I replaced one in my dads ram and it was missing blades at only 55K. His overheated in exactly the same way yours does. Usually when the temp increases at highway speeds its the water pump. I wouldn't waste my time messing with the AC coil. If it was plugged bad enough to cause an overheat it would be pretty obivious. Unfortunatly there really isn't a reliable check for the water pump (circulation). But I would bet money on it, As your symptoms are pretty much textbook bad water pump.
 

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Discussion Starter · #10 ·
Well it turns out the water pump is fine but the timing chain cover where the pump seats into is corroded out. Here are some pics. I'm now in the process of removing the timing chain cover to replace it, but I'm also having second thoughts. I've read a number of threads on this forum about overheating problems and something tells me that replacing the chain cover isn't going to solve my problem. The corrosion doesn't look pretty, but I'm not sold that this is really impeding the water flow from the pump. Maybe I'm just being pessimistic.
 

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Where did all that displaced material go? Are there any small water passages that could become blocked/clogged and make more problems?
 

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Discussion Starter · #12 ·
I haven't found any of the material yet...I still need to remove the radiator and flush it out back wackwards though. Since it's a sideways radiator I suspect it has all collected on the bottom of the inlet side.
 

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WORLD'S GREATEST TRUCK
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next time you wonder what all that crap coming out of the lower hose is...
 

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mahilly, just ran into that same problem myself.the timing chain cover assembly was all corroded.let me ask you how you removed the crankshaft damper.what type of puller did you use .and did you use the special assembly tool. any advise would help at this point. thanks
 

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Discussion Starter · #15 ·
I used a harmonic damper puller that I rented from Autozone. They have a whole line of obscure tools that the loan out. It's pretty much impossible to get the damper off without the proper tool.

I have the replacement parts now - thanks to cbrenn71 - so this weekend I will be putting it all back together again. I'll let you know how it went when I'm done. My advise thus far - make sure you have a complete set of metric tools. That Dodge engine was NOT made in America.

Which reminds me - if anyone can tell me the factory torque specs for the chain cover and water pump I would really appreciate it (I ordered the FSM from dodge two weeks ago but I think they lost my order).
 

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well mahilly i got as far as you did but dodge needs a week to get me the parts.the cover is 320dollars and the gaskets and seals comes to another 45 dollars.plus dodge said they changed the inlet hose diameter to the cover so a new hose is another 28 .this is my only vehicle so i need to put it all back together and re do it next week.this sux! let me know how things went.
 

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Hummer Recovery Vehicle
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dang, 320 dollars..... mahilly got a heck of a deal from me! i should have charged more. lol
 

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cbrenn71 thanks for not telling me the price.i felt like i was punched in the stomach when they told me how much the parts were going to cost.i just finished putting it back together. just to pull it all back off next week.guess this was my practice run.i wonder how many d's with the 4.7 have this problem i know its not from lack of maintenance i flush the system once a year.
 

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Discussion Starter · #20 ·
Putting it all back together was a lot easier than getting it apart. The gaskets are self sealing so you don’t need any sikaflex. Just make sure you scrape clean all the mounting surfaces. The only tricky parts were getting the A/C compressor and Alternator back on their mountings, and replacing the harmonic balancer. The A/C and Alt. have compression fittings where the mounting bolts screw into the back side. Bang on these a bit to widen out the spacing so they slide easily over the mount. The harmonic balancer is tight going back on. You need to get it in there about an inch before the center bolt will reach the threads. I had to hold a small block of wood against the center of the balancer and tap it with a hammer to get it in far enough. There is very little room to swing a hammer so I just had to keep tapping for a while. Once you get the bolt in the threads you can screw it in the rest of the way. Not sure if they make a special tool for this??? Anyways, it’s running much cooler now so the replacement seems to have done the trick. However, the temp does still creep up a bit in hot weather. I think I still have some air trapped in the system. After reading some of the other threads on this forum it think the 4.7L engine has a real problem trapping air. One person explained how they jacked up their front end using a 60” jack to burp the air out. It seems to me that having some trapped air in the system over a long period of time may have contributed to, if not caused, the corrosion problem. The "corrosion" actually looks like wear caused by turbulence or cavitation (just my theory though).

The good news: Having the timing chain cover off gave me a good look into the belly of the engine. There is NO SLUDGE after 84k miles!!! The timing chains look as good as new and the tensioners show no visible wear.

Cbrenn71 – you definitely gave me a good deal, and I thank you once again. I hope you don’t feel cheated. I wasn’t aware of the replacement cost until after I got your part and went to buy the gasket.

Jet tech – good luck. Let us know how it goes.
 
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