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Matt Hardy
Matt Hardy, ASE Certified Technician
Category: Dodge
Satisfied Customers: 920
Experience:  ASE Master Auto Tech, ASE L1, Jeep/Chrysler Dealer Tech, 18 yrs exp
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Dodge Dakota SLT 2003 dodge dakota with 4.7 liter. coolant

Customer Question

2003 dodge dakota with 4.7 liter.
coolant fills resevoir, then vents. if i periodically siphon resevoir i can pour it back into radiator.
never seems to overheat, untill radiator gets low. as soon as it rises slightly above normal i add fluid from the overflow resevoir.
have had it pressure tested and also gas tested from the radiator. no leakdown and no exhaust gas in the radiator.
air in the system?
Submitted: 3 years ago.
Category: Dodge
Expert:  Matt Hardy replied 3 years ago.

Matt Hardy :

Hello and welcome to Just Answer, my name is Matt.

Matt Hardy :

Let's start by bleeding the air from the system.

Customer:

okay

Matt Hardy :

Look by the upper radiator hose...where it connects to the engine...see the fitting? It is a hex fitting

Customer:

yep, did that.

Matt Hardy :

you took that fitting out to bleed it?

Customer:

not all the way. parked slightly uphill, topped it off, ran it, opened the bleeder, when coolant started coming out i tightened it back up. also read about filling it, starting it, running up to 3000 rpm for 10 seconds

Matt Hardy :

You might be OK as far as air in the system, but the correct procedure is to pull the fitting and fill it until it comes out...with the engine OFF

Customer:

okay. i'll try that. also, making noise when i shut it off. thought it was ac, but isn't the heater core over there too? not losing fluid tho, till the resevoir fills up. then i lose it. why does it keep backing up into the resevoir?

Matt Hardy :

If coolant keeps going into the reservior....then the pressure in the cooling system is exceeding the pressure rating on the cap. Either the radiator cap is faulty.....or the engine is overheating....which creates excess pressure---which goes to the reservoir.

Matt Hardy :

Or....a head gasket is bad....which causes excessive pressure in the cooling system

Matt Hardy :

So it's either the cap or too much pressure

Customer:

so i should try replacing the cap again.

Matt Hardy :

either that or have the cap pressure tested

Customer:

how do you have the cap pressure tested?

Matt Hardy :

you have to use a cooling system pressure tester...with an adapter for the cap. possibly the auto parts store will have one you can use

Customer:

mmm, sounds like easier to just replace cap

Customer:

had the system pressure tested (i watched) and no leakdown. could there still be a leaking head gasket?

Matt Hardy :

It is possible. It is hard to detect a leaking head gasket, when it's not very bad.

Matt Hardy :

There is a special test for this as well.

Matt Hardy :

4.7 is easy to get air trapped in. I would focus on that first

Matt Hardy :

Let me tell you about a 'trick' I use to bleed these.....

Customer:

okay........

Matt Hardy :

first, bleed from the hex fitting, as we discussed earlier

Matt Hardy :

then

Matt Hardy :

you will need an extra radiator cap

Matt Hardy :

see how the cap has 2 seals on it?

Matt Hardy :

cut off the smaller seal....the bottom one

Customer:

i'll go get it

Matt Hardy :

fill the radiator

Customer:

okay, i see it

Matt Hardy :

cut off the smaller seal, the bottom one

Matt Hardy :

fill the radiator, and the reservoir

Matt Hardy :

put the modified cap on

Matt Hardy :

then start the engine

Customer:

fill the resevoir all the way? or just to the full mark on the stick?

Matt Hardy :

what stic k are you referring to?

Matt Hardy :

Oh, sorry, now I remember....dodge has a stick...I was thinking of Jeep

Customer:

ok

Matt Hardy :

it doesn't matter, really. anyway, start the engine, and any air will go past the missing seal and go into the reservoir. and coolant should go back into the radiator to replace the air.

Matt Hardy :

it's a good way to do it...less mess

Customer:

i'll give that a try tomorrow. thanks :)

Matt Hardy :

just remember to put a good cap on it when you're done

Customer:

hey, would a simple compression test find a leaky gasket on one of those 4.7's?

Matt Hardy :

Not usually...it would have to be pretty bad...you would have a misfire

Customer:

i have a compression tester, it's just such a hassle to pull the plugs

Customer:

why would you have a missfire?

Matt Hardy :

if you has low compression, the check engine light would be on, and there would be a misfire code

Customer:

had that happen. turns out it still had OE plugs :( new plugs and 60 miles or so cleared the trouble code.

Matt Hardy :

if the code cleared on it's own, that is a really good sign

Customer:

plug in the #2 had dissapeared electrode. all other plugs were looking at around 1/4 in. gap instead of 40 thou

Customer:

anyhow, i hope it's just air. thanks for all the help

Matt Hardy :

someone got their money's worth out of those plugs!

Matt Hardy :

you're welcome. thanks for using Just Answer again.

Matt Hardy, ASE Certified Technician
Category: Dodge
Satisfied Customers: 920
Experience: ASE Master Auto Tech, ASE L1, Jeep/Chrysler Dealer Tech, 18 yrs exp
Matt Hardy and 4 other Dodge Specialists are ready to help you
Customer: replied 3 years ago.

Hey Matt, you still there?

Today i siphoned all the old coolant out of the overflow resevoir and filled it back up to full with fresh coolant.

I removed the bleeder bolt and topped off the radiator. I tried your trick with the old radiator cap, but couldn't tell if it was working or not. After about ten minutes i could still remove the radiator cap???

Shouldn't it have been pretty hot? I just drove it home from work (30 min drive) and it had only been sitting about 15 minutes before i started tinkering.

So i opened the bleeder again and let it run for awhile, watching the air bubbles and occasionally adding a little more coolant.

Ran it approximately 45 minutes. Shouldn't the thermostat have kicked open and it start spewing coolant out of the cap and bleeder i had opened?

Where is the air still coming from?

Expert:  Matt Hardy replied 3 years ago.

Remember, do not run the engine with the bleeder fitting out.

All you do is fill the radiator until coolant comes from the bleeder hole, then put the fitting back in. This does the initial bleed. Then do the cap trick to get the last air out. The system will not build any pressure with the modified cap on. Then install the regular radiator cap and see if the cooling system builds pressure. The upper radiator hose should get a bit firm.

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