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Discussion Starter · #1 ·
I am about to the point of pushing this truck over a cliff.  But before I go through with that overly dramatic affair I figured I would ask around for help.  I recently joined this forum since every time I search for issues this forum comes up. 

But the back story:

my Dad got this 90 W150 in 1992 with 56,000 miles.  He put in a reman engine and trans around 100,000 miles in the mid to late 90's.  Now I get conflicting stories from him, but he was never able to get a clutch fan to work once the original clutch went out. However I have heard him say that the cooling issues started once the reman engine went it, to him changing out the original clutch, to him changing to this radiator.  But he ended up putting on a 6 blade fixed fan and claimed that "cured" his cooling problem.  Well that may work on the backroads and highways of central PA, but does not work in Pittsburgh PA traffic.

But fast forward to when I took maintenance ownership.  The truck would run fine at highway speeds and back roads driving with his straight fan set up.  If it sat for any amount of time at a light, the temp would slightly increase, but would go back down once you started moving.  Once I got the A/C charged, the temp would creep up to the top of the safety zone if stopped in traffic, but would eventually go back down again once you got moving.  That was okay until I got stuck in traffic trying to park at a concert.  The truck was on the verge of over heating and no amount of reving would cool it down.  At this point the cab temperature raised and thats when I said I had enough, a clutch fan would go back on.  Knowing my old mans issues with it in the past. I got the Hayden 2797 clutch and a 7 blade clutch fan from some other mopar (truck originally came with a 5 blade clutch fan) and thats where we are today...

It runs worse with the clutch fan!!  First time I had it out the gauge would fluctuate around the bottom of the safety zone then went straight for the hills and over heated (gauge went outside of the safety zone).  Luckily I got to my destination and was able to shut it down.  Then it was jumping from store to store to try and get it home without blowing the engine.  So the first thing I did was change the thermostat out since it was last done 17 years ago at 166000 miles (it has 209077 now).  Well I installed that Monday night and took the truck to work Wednesday.  Traveling the 8 miles to work in suburbia/back roads path I took, the engine did run warmer than it did before, but never got outside of the safety zone.  I was trying to tell myself that is okay, but on my drive home stuck it a little heavier traffic, it went above the safety zone...

Seeing that the cooling system hasnt been flushed in 3-5 years, I figured it was time (and may contribute to this issue). When my dad flushed the system, he would attach a garden hose to an attachment on the heater hose then open the radiator cap.  Run the truck until the water came out clean, added new coolant and away he went (he did this every 3-5 years regardless of mileage).  I wanted to do something similar but decided I should probably use one of those cleaners/flushers you can get at the parts store.  So I ran water through the system last night to clean some stuff out (like the directions tell you to do), then I added the cleaner and distilled water.  So over the next few days Ill be driving the truck to work to run that stuff through.

The water pump was changed about 2 years ago, with maybe 20,000-30,000 (at most, dont have the maintenance booklet with me) on it.  The thermostat is new as of this week.  I know the radiator was replaced, but since I dont have the booklet with me I cant confirm when.  With both fan set ups the factory shroud is in place.

I figured I would charge the a/c again since I would be driving it more (since it all leaked out. AGAIN. only 1 or 2 months and 100 miles on the previous charge... need to find the leak, tried last night with no luck.  but thats another problem for another day) and I noticed idling in the drive way with the radiator cap off (and with it on), the truck did not over heat, the gauge was reading where it normally would.  But in drive with your foot on the brake, or up a hill, or just looking at the gauge while on the road causes it to over heat.

Seeing this is a truck, built in the 1990's I do not feel I should be having this much trouble with the cooling system.  That gauge should go to the normal spot and stay there.  I am not hauling a a heavy load up a hill in hell trying to get out of there.

can anyone help me with this cooling issue? the fixed fan seems to work better, but still is not suited for driving in pittsburgh. And that clutch fan... isnt working.

Ideas?


 

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Do you have a fan shroud?  Have you thought about having the radiator tanked and flow tested?  It may be cheaper in the long run to just replace the radiator, but I hesitate to say "just replace ____" without something to back it up, but it may be worth it depending on how old the current radiator it.  If it's a stock style brass and copper radiator, it's been a while since it was replaced as I don't think those have been available for years now.  Also note that the radiator cap is critical and must be the correct pressure in order to prevent overheating.  The cap should be a 16 lbs cap.  If it doesn't hold pressure, it lowers the boiling point of the coolant and it will overheat.  Also engine timing can play a part on the engine heating up so that is worth checking.  Remember that on a TBI truck, the coolant sensor needs to be disconnected to lock the timing adjustments out in the computer to set the timing baseline.
 

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Discussion Starter · #3 ·
Yes I have the factory fan shroud on there.

I have not thought of getting it flow tested.  But if it cools while traveling with the fixed fan and only heats up at stop, does that tell you its radiator flow?  (still learning things here so bare with me)

The radiator is a single row aluminum one with crimped on plastic tanks.  I really should of brought the maintenance book with me to work (i brought the service manual instead).

The radiator cap is a 16 psi Stant model with the red lever on top.  the spring does look a little rusty.  However last night when I took the truck for a ride I swapped the radiator cap that is on my 68 Dart (same model and pressure cap as the truck).  I believe this cap is good because it was on the dart for a 1300 mile round trip to OBX last week. However when I traveled above 70 mph with the dart the radiator did loose coolant.  But either way that car did not over heat ( I was thrilled).  But anyway switched caps and no difference.

Well that is good to know about how to check timing on this truck. So the coolant sensor needs to be disconnected by the thermostat housing?  or is there another one?  I know on carburated vehicles if the timing is off the temp is always off.  But if the temp is only running hot at a stop with the fixed fan, would that still mean the timing is off?  I do have a timing light, and if I am correct on which coolant sensor to disconnect I can try and get the timing reading tonight (first TBI vehicle for me, so please bare with me here)
 

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The temp sensor is up front, but it's a two terminal plug, not the typical Mopar sending unit with the single stud on top.



The timing is a shot in the dark, but it doesn't cost anything to check. An engine running lean, either due to fuel or timing, will run hotter and if it's on the border, it can push it to overheating at idle.

If your radiator is the aluminum and plastic tank type, it's been replaced recently. I personally hate the single core radiators. In many cases Dodges are know to be "cold natured" and will typically run cooler than a lot of similar vehicles. I still stick a piece of cardboard in front of the radiator on my Ramcharger just to get heat out of it in the winter. But the single core radiators are just trouble in my opinion. I would almost rather step back a few years and spec out a 2 or 3 core or maybe an aluminum "racing style" radiator and not have to worry about it. But I would only do that if there is something wrong with your current radiator. Unfortunately that means testing it, but the cost of that can vary. A new 2 row is probably going to be around $200, so it's not exactly cheap.

But basically you need air flow through the radiator, this means unbent fins, unobstructed grille and a good fan and shroud. You need flow through the radiator, this means a good pump with a good impeller, a thermostat that works and no obstructions in the water jacket, hoses or radiator itself. And you also need pressure, which means a good cap and no small leaks around hoses or gaskets that could release the pressure. And lastly, you need a proper mix of antifreeze and water to ensure the boiling point is where it needs to be. Other than that, there isn't much more to a cooling system, though other things like a blown head gasket or running lean can have an effect on the engine temperature.
 

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Discussion Starter · #5 ·
Yes that is basically the break down of the system...

But lets look into what you said a little deeper:

-you said something about a good pump with a good impeller.  What do you mean by good impeller?  as in an impeller that is actually made and dimensioned correctly?  or are there different part number water pumps out there that would have different impellers? Knowing my dad he would just go for the basic stock cheap replacement pump

-Well I know the proper mix of antifreeze was in there (now its water and that cleaner/flush stuff).  So hopefully once I am done flushing the system I know that there should be no obstructions within the system (maybe the radiator, but I guess I wouldnt know unless I get it flow tested). 

-Now you said use a 2 to 3 row radiator.  I know when I looked a couple years ago I did not find any radiator that had more rows than one.  I even looked at the 250 and 350 variants and came up with nothing.  Is there a radiator company that makes a radiator for these trucks that meet the 2-3 row specification and still mount up to the rad support and fan shroud? I know that is asking a lot of a replacement radiator for something this old.

-I dont believe there is a blow head gasket.  No smoke and smell from the exhaust.

-The grille is unobstructed.  The only things in front of the radiator are the condenser, trans oil cooler, and grille.

-We did talk about the timing.  I can easily do that now knowing i have to unplug something.  So I am good there.

-You also mention running lean.  Since its a TBI you really cant adjust the mixture manually(?), so I guess that means to check the lean condition I have to do a fuel pump pressure test? Now I have read a couple posts on this forum and the first step everyone says to do for diagnosing problems on these systems is a fuel pressure test.  The service manual on page 14-3 explains a fuel pump pressure test.  It says I need a the fuel system pressure tester C-4799A.  I dont have one of those.  I have a vacuum/fuel pressure gauge.  Can I use that gauge?  It also goes onto to say use Actuate Outputs Test "Auto Shutdown Relay".  What is that?  or is there an easier way to check fuel pressure?
 

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Discussion Starter · #6 ·

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there are 2 different fan directions on dodge trucks , the older L/A motor's turned the fan one way while the newer magnum motor's turn the fan the other way ...  there are 6 blade water pumps and 7 blade pumps , the taller radiator there ( 21 inches ) will fit under your hood , napa had them in 4 row , for less than shown there ... I use them on some of my L/A motors , look at the overflow hose nipple , that is the difference between the right one and the magnum one , their pointing in the other direction.....
 

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We've had a couple discussions about water pumps and I remember a couple posts mentioning some cheap pumps that had fewer blades than other pumps.  I remember years ago when I street raced, I used to use a pump from a company called FlowKooler on my big blocks that usually had an extra blade or two.  I've also seen people comment on forums where an old engine had the impeller pretty much rust away or become broken off them pump shaft.  I doubt that sort of thing is a common occurrence, but with the quality of chinese parts these days, nothing would surprise me anymore.

On the radiator, it can vary what parts were available from the factory depending on options and specs and the parts available from the aftermarket suppliers.  I find that the options narrow down sometimes with aftermarket parts as you get later in the years.  For example, Rockauto only lists single row radiators for your '90 but if I step back to a '84 W250 with a 360, you can find a 3 core.  Looking at the '90-'93 Mopar Truck Parts Manual, there were several radiators available depending on the truck, engine, A/C and the "Max Cooling" option.  Aftermarket parts houses are always trying to consolidate things down to apply more individual part numbers to more vehicles to lower their inventory and associated costs.  So you end up with less options now then what you should have.  But again, you can usually tweak it a bit by looking at a 3/4 or 1 ton, which usually had the heavier options and you may find things that will fit and be an upgrade over what you have stock, or what is available due to the near useless catalog systems the aftermarket parts places use.  As long as you are looking at a '81-'91 Dodge D/W series truck with a small block V8 (318 or 360), it should bolt in and the hose ports should be the same.  Even the older '72-'80 models could be made to work, but somewhere around the body change they moved the bolt locations around a bit so new holes would have to be drilled in the core support or radiator flange.

With TBI it's mainly fuel pressure and the spray pattern from the injectors themselves.  The tool part numbers in the Factory Service Manuals are for Miller Specialty Tools, which I believe is part of OTC now.  They are ridiculously expensive and you can easily find a serviceable replacement without having to buy from the company that supplies the dealership's tool.  You can use just about any fuel pressure gauge as long as you can adapt it to the fuel lines and it will read in the correct pressure range.  TBI runs higher pressure than a carb, so a fuel pressure gauge for a carb engine would not be much use as it should peg the gauge.  Your FSM should give you the correct pressure range so you can see if your gauge will work.  Without reading up in FSM I am not sure on the Auto Shutdown Relay, but I would suspect it's basically just a test for the fuel pump relay to check that it is working in the case of a zero pressure situation.  That is all the ASD relay is, is the fuel pump relay but it shuts off the fuel flow when needed so they call it an ASD.
 

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That's a good clutch if it's working... When the engine is hot, stop the engine and check to see if the fan is locked/high resistance to turn (good) or loose (bad).

Second, make sure the shroud and fan are in good condition and properly positioned. Fan blades should be about half way into the shroud. Also, double check that you have the correct fan (correct rotation) and that it isn't on backwards.

Lastly, no way is a single-core radiator going to be enough in traffic with an AC condenser blocking airflow, even if it's clean. I would 1 - clean out the condenser fins with a strong stream of a hose (not a pressure washer) and make sure all the fins are clear. If you have a separate transmission cooler, same thing; and 2 - I would use a 2-core aluminum or 3-4 core brass radiator.
 

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Discussion Starter · #10 ·
Okay.

  That is a good test to try on the fan.  I will try when I get home after work since I know the truck will be hot.

  Fan rotation is correct, blades are oriented the same way the fixed fan was.  Plus with the design of the blades, you can only install the fan clutch one way.

  As I posted before I did find a 2 row aluminum radiator, then I just found a 3 row brass radiator for a 90 W250.  So I will have to see about getting one in, if possible.

  Okay, I will look at the gauge I have tonight.  I know the service manual says the pressure at the throttle body should be 14.5.  That may be the upper end of my gauge.  But I will have to see what connection is on the line. Unless someone here knows what connection is on there already? If it is a hose connection that would be simple to adapt to, but if it is some kind of flare I would need the appropriate mating component.

  So to check the fuel pressure I have to first relieve the pressure that is in there. How do I do that?  Then I guess I just disconnect the line, connect my gauge and turn the key to on and observe the pressure?  I believe from there the manual goes into what to do next depending on the pressure reading.  If low check the pressure at the tank at multiple areas.  Does that sound right?
 

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Discussion Starter · #12 ·
Update:

So I have the cleaner flush stuff and distilled water in the rad now and on my way back from work it wasn’t getting as hot. Well I was playing around with the a/c on and off since it was raining but it appeared that it seemed to cool better once the a/c was on. What if the clutch is to far from the radiator? Could I put a spacer that would still have the fan part way out of the shroud but closer to the radiator to sense the hot coolant better?

By the time I got back to my place it was at the top of the safety range again. Shut it off and tried to spin the fan. Fan maybe spun 30-60 degrees before it stopped. So it seems to be working

HOWEVER! Once I got the truck down in the drive way and started it back up again. I left the truck idle in park and the temp gauge went down!!! Why at a traffic light and while driving would the temp go up, but then cool when idling in park?!
 

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make sure that IS what its doing , not just a fluke , but an automatic trans ? low fluid ? or a converter going bad ? I'd be carefull suspecting that though , untill it showed other signs , like locking up or not moving ... IF the fan is "IN" the fan shroud and almost as big as the hole its in , then no spacer is needed , it need not be VERY close to the radiator .  a new thermostat ( 190') , a good fan clutch , fan drawing air ,(  with the correct curve to the blades ), a clean radiator core , and a good water pump .. TOO much pure anti freeze can also cause problems ... 
 

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Excellent point.  I have been boycotting automatics for so long I didn't even consider the heat they would put in the radiator.  It might be a long shot, but it's probably worth investigating.
 

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Discussion Starter · #15 ·
Blades are about 2 7/8 wife from the front to the rear of the blade. About 1.75” are sticking out behind the shroud. The blade tip is about 2.5 inch’s from the ID of the shroud opening

How would I go about finding out if the trans is adding to much heat? The fluid isn’t discolored, it doesn’t smell and it’s in the safe range
 

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Although I don't think it's likely in your case, I'd check the thermostat too to be complete because it's a simple test. Thermostats and voltage regulators have very bad quality control. Pull it out and put it in a pot of boiling water (212 F). Make sure it's opening all the way, not sticking, etc.
 

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KurtfromLaQuinta said:
If the trans fluid looks clean and pinky and it smells good- not burnt... most likely you don't have a transmission problem.
The only time I had cooling issues in the past like yours was because of a slow flowing radiator.
agreed , I'll lookie see the diameter of the fans vs/ opening in shroud today ... what happens is like this , everything gets a little clogged with age muddy stuff builds up IN the block down low , the openings of the rad cores get corrosion in them , the blades of the water pump wear , fan clutch gets weak , rust scale inside steel parts ect . all this adds up and soon the extra load of traffic and warm weather ... your running hot so you can fix 1 thing and still have the "problem" because its not just that 1 thing . BUT you have to know its fixable , and not give up too easy ;) because your has had the fan changed , lets start there , I'll get a photo of a stock one and its shroud for you to carefully compare .. this is a L/A with an L/A fan shroud centered and attached to one of the "taller" radiators ... in a 1991 W250 318 pic 2 is a magnum stock 318 ( flat belt) it is not inside shroud
 

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Couple tidbits here from my ventures into the temp world on mine.

Not all water pumps are created equal. Number of blades, diameter of impeller, design of blades, etc. There are some pretty wide variances there. I ended up going with a FlowKooler on mine as well, which really seems to work well. I also hogged out the ID of the intake manifold where the t-stat goes so it would accept a Robertshaw style stat which can handle more flow than the stock design. Took about 5 minutes with a die grinder and carbide burr.

Next up is the radiator. I have a local shop that still has catalogs, and people that know their stuff, so they were able to source an old-school 4-row Modine. As mentioned, a single row aluminum will be pushing it on that thing, go with at least a 2 or 3.

Fans...more blades is NOT necessarily better. I actually had better luck cooling with the wide bladed 5-blade that came on mine, rather than the 7-blade I grabbed from a W250. More angle, different blade design, all helped in that aspect.

Trans heat...definitely check the fluid. You can also use a laser therm, see what kind of fluid temps you have into the trans cooler. I have both the stock cooler in the radiator and the secondary air-oil cooler in front of it, factory spec. My dad pulled the stock one, put on a finned one below the radiator, didn't work as well as the stock one, so I put the stock one back in, but I did see a slight increase in coolant temps at certain points.

Also check your O2 sensor. Pull it, see what the tip looks like. I found the stock O2 was running the system REALLY lean. Swapping to a Bosch went the other way, pretty fat, but the NTK sensor actually reads pretty solid. That along with checking fuel pressure and timing are good places to start.

I've got another thread on here buried, might be worth a read, just for food for thought.
 

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Discussion Starter · #20 ·
I attached the pics of mine.  The clutch fan that I have is not as close to the shroud as yours.

I reached out to Hayden and they said to use the stock fan in place of the 7 blade I have on there... I know my dad still has the fan in the part shed but I wont be able to get to it for a couple weeks. They also said that the amount of blades arent as important as pitch. 


Well I put the fixed fan back on the truck and it will stay cool at speed (way better than the 7 blade clutch fan).  However it will heat up when idling in park and neutral.  I did the hand in front of the radiator test on both of them.  I do feel a lot more air coming through the radiator when in park when the 7 blade clutch fan is installed.


As I mentioned below, I did find a place where I could get a 2 row aluminum and a 3 row brass.  So I may get one of those as well as install the original 5 blade fan when I can get it.


What would I be looking for on the tip of the O2 sensor?  I still need to see if my fuel pressure gauge can read as high as this system goes.  I also still need to check the timing ( which a member here instructed on how to do so).  How do I check if the O2 sensor is having the system running lean or rich? by the look of the tip? Or is there a way to check by looking at voltages?
 

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