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jlknolla
Dodge Dakota
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12/03/2008
10:14:36
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 Subject: Cooling System Question
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'99 5.2 4X4 44RE Auto 170,000mi
Still working on this cooling system question and trying to decide on having the waterpump replaced or not (hate to pay for a job I can do myself but I need heat). I am away from home and the RV park I am staying at does not allow vehicle maintenance on the premises - most of my tools are at home and not with me but I have a good 100 piece portable set with me.
NOTE - Thermostat is removed due to previous overheating problem.
Engine currently runs fine, starts and warms up (the engine, not the temp gauge), plenty of power, normal gas mileage, but no heat in the cab.
I drove it 600 miles from Albuquerque to Salt Lake City at highway speeds on Sunday, (had an earlier 900 mile trip from Little Rock to Albuquerque a few weeks before that) no issues at all on the road - although I suspect the belly pan gasket in the intake is leaking again (this will be 3rd time - I started getting the funny oil pressure/loss symptom the belly pan is known for on the way to SLC).
Top radiator line gets pressurized after driving or running for a while (5-15 minutes), literally feels like it high steam pressure, not water pressure. If you feel the hose it is hot to the touch, but does not feel like much coolant in it.
Today I blocked off a portion of the radiator on my 12 mile drive into work and the temp gauge came up to the bottom of the normal arc, still no cabin heat.
I thought a while back that I may have had a head gasket leak (causing the pressure in the upper hose) - while running I would see very small bubbles in the coolant at the filler neck.
Before tearing into the engine and changing head gaskets I tried a head gasket seal product (mixed with water and run through the engine, air dry for 24 hrs, refill with coolant/water). I followed the directions - no more bubbles in the coolant but still seeing the pressure in the upper radiator hose.
There is no evidence of coolant in the oil or oil in the coolant at this time.
Line to heater core is hot, line from heater core is cool. If I remove the cap on the fill fitting in the heater line coolant will flow out slowly, it is hot but not under much pressure or flow.
I am thinking about putting a new T-stat in and seeing what happens but have a couple concerns - so here are the symptoms:
1 - if I pinch the upper hose (which gets very hot), I only feel a little coolant running in it, feels like mostly air or steam
2 - I have a lever activated 16# pressure relief cap on - I can lift the lever, discharge the pressure and then open the cap even with the engine running at temp - coolant is hot but does not spray out or flow like crazy
3 - if you run the RPMs up with the cap off the coolant level drops a bit and then will slightly overflow when the RPMs go back to idle (idle is very solid/steady, less than a needle width variation)
4 - overflow reservoir appears to be functioning, when really hot the coolant passes the pressure cap (sounds like it is boiling), and when it cools it pulls it back out
5 - I changed the plugs recently and there was oil and carbon fouling but no evidence of coolant
6 - coolant level does not change
I figure it is one of the the following:
A - not enough coolant/not a good 'burp' on the system when I refilled the system after any of the attempts to diagnose/fix this - I have a flush/fill fitting on the heater TO line but can never seem to get enough coolant in (it only took 1.5 gallons of 50/50 premix to 'fill' after draining the system the last time - I did not pull the drain plugs, only opened the drain valve on the radiator)
B - waterpump impeller is corroded and not flowing enough coolant - this is my chief suspect at this time but the fact that the level moves when the engine is revved makes me question it
C - radiator is blocked (I did not change the coolant regularly, it was the original orange 'lifetime' stuff until I pulled the intake for the belly pan gasket about 5 years ago) - the whole face of the radiator does seem to warm up, and there are no issues I am aware of with transmission cooling so I am not sure if this is it but it is original equipment and I did not do any maintenance to it to speak of over the last 10 years
Any other ideas or suggestions on how to best troubleshoot this given my limited tools and facilities?
Thanks
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Its me again
Dodge Dakota
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12/03/2008
12:13:23
|  RE: Cooling System Question
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Maybe I missed something,
But, it sounds like you need to unplug and or flush the heater core!
Have you tried flushing it? If I missed it in your LONG post, I'm sorry, then, nevermind.
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jlknolla
Dodge Dakota
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12/03/2008
12:50:53
| RE: Cooling System Question
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its me,
No I have not backflushed the heater core but I am fairly certain right now that lack of heat is a symptom not a cause - that said, I may be able to try and do this tonight by disconnecting the heater return line and feed line from the pipes on the waterpump housing and then trying to blast pressurized water back through the return line.
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daddio
Dodge Dakota
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12/03/2008
13:56:19
| RE: Cooling System Question
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the engine will also never get to proper operating temp without the tstat. it could be any of these 2- 1) air in cooling system, 2) heater core plugged up. if it's overheating and you still get get hot air in the cab it has to be one of the two things i mentioned.
i would backflush the heater core, install the tstat, then refill the system and when refilling, leave the rad cap off and run the engine until it reachs normal operating temp, topping off the fill as needed until it at temp.
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jlknolla
Dodge Dakota
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12/03/2008
14:36:48
| RE: Cooling System Question
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Thanks daddio,
Any easy test for blockage in the radiator? It drains fine through the drain valve, and there is hot water in the radiator when operating.
I really find the lack of coolant flow through the upper hose to be indicative of a bad pump or air in the system but I have tried a number of different ways to bleed the system (literally had the front end up on ramps at one point with the cap off to try and burp the system and the Haynes book does not provide any real recommendations for a good fill procedure to avoid air in the system.
I will try and backflush the heater core first, then replace the T-stat and fill the system slowly and see what I end up with.
Any recommendations for a good bleed procedure to get the air out?
Any other ideas?
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daddio
Dodge Dakota
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12/03/2008
15:03:15
| RE: Cooling System Question
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i've never had any problems with mine when i drained then re-filled through the radiator cap opening as the engine got up to temp.
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onearmsteve
Dodge Dakota
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12/03/2008
22:48:46
| RE: Cooling System Question
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how about it was overheating the first time because the t-stat was bad and stuck closed so u took it out maybe just put a new one in and it will be fine just make sure u burp the system good it will make it run hot and if u see water moving when u rev it the water pump is working.
A LOT OF T-STAT GO BAD EVEN BRAND NEW ONES
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.boB
Dodge Dakota
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12/04/2008
03:14:22
| RE: Cooling System Question
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The problem is that there is no cab heat. Do you get heat from the defroster vents?
The heater is simply a small radiator. Hot water through the core, air blown across the hot core.
If the fan is off, and the heater doors are closed, you would get hot water going into the core, and only slightly cooler than hot coming back out. That would be normal.
If you get a hot water going into the core, but the other hose is cool, then water is not circulating through the core.
You can try backflushing with a water hose. That might improve the situation a little bit. IF it does, then the core is clogged with schmutz.
I would try this. Remove both hoses from the heater core. Connect two hoses about 2' long, and attach them to the hood so they point straight up. From the cold side of the core, pour in pure coolant flush, like Preston radiator flush. Let it sit overnight, then flush again with a garden hose. Connect everything back up and refill the system.
If that doesn't work, you'll have to replace the core. I don't envy you that job.
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jlknolla
Dodge Dakota
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12/04/2008
14:51:30
| RE: Cooling System Question
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Thanks guys,
Tomorrow I will disconnect the heater core feed and return lines and hit it with pressure water for a backflush, then I am installing a new 180 T-stat and carefully filling the system.
I first removed the T-stat when I last did the intake belly pan gasket a few years ago, put a new one in and it overheated right away, checked the T-stat in hot water and the new one was bad, got a replacement but never put it in - has run fine since, just a little cool.
Curious if there could be a small head gasket leak - other than the steam pressure in the system, there are no other symptoms - truck is really running fine.
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.boB
Dodge Dakota
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12/06/2008
12:33:16
| RE: Cooling System Question
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Head gasket is a possibility. Take a collant sample to a repair shop and have it tested for products of combustion.
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jlknolla
Dodge Dakota
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12/08/2008
20:50:26
| RE: Cooling System Question
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Well I would feel stoooooopid sharing this but perhaps it will be of help to someone else.
I finally got around to backflushing the heater core - because it was snowing here in Salt Lake City today.
After much struggle with the heater return line (would not come off the pipe from the water pump housing), I finally used a coin-op car wash rinse line and blew out the heater core.
Flow was VERY slow at first, and looked almost like mud, then muddy water, then orangeish water, then clear water with good flow.
Put it all back together, fired it up, blocked the radiator (still no T-stat), and immediately had heat in the cab.
More interesting, though, is that the pressurization problem on the upper radiator hose is gone - completely gone. I am guessing there was an air bubble at the top of the pump housing where the heater return line was, and I was getting pump cavitation.
All is well, will put the T-stat back in this weekend.
Thanks for the suggestions on the heater core, I'd have never guessed it could have such a big impact.
Now for that blankety-blank-blank intake manifold belly gasket......
Thanks again.
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.boB
Dodge Dakota
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12/09/2008
10:04:32
| RE: Cooling System Question
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Glad that turned out so well. Changing the core is a real bear.
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