420A Wierd over heating problem

[Stee420aT]

My 420aT is over heating. The gauge is all over the place but once it stops going up and down, after about 5 minutes it pegs hot. Its blowing so much coolant into the overflow and the overflow is "overflowing" loosing gobs of coolant. I've burped the systems, ive replaced the t-stat. What i really want to know is the proper way to bleed/flush the system. I can't find the steps anywhere on this forum, i use the search tool. I would like advice AND the steps to properly flushing/bleeding the 420a motor.

Thanks guys!

 

[GSexx]

To bleed it fill up your rad and your overflow to normal. Take the rad cap off put a funnel on the opening and turn the car on with the heat on high. This will let any air out of your heater core. As the car gets to temp you will see all the air bubple up and out of the filler neck. When the fans kick on you know you're done! Also as for the gauge try to replace the xoolant temp sensor and fan switch I'm guessing they are old anyway and it can't hurt. As for the coolant overflowing it is most likely a blockage in the system ex (improperly installed head gasket) or the turbo. Is the turbo water cooled?

 

[Stee420aT]

Turbo is oil cooled, aux fan doesnt ever turn on but that doesnt explain the fluctuating temp. I will try a coolant temp sensor and doing a proper flush but im starting to suspect that its a head gasket. it doesnt smoke and it runs fine but that doesnt mean its not the head gasket obviously.

 

[BogusSVO]

The gauge is all over the place but once it stops going up and down, after about 5 minutes it pegs hot.
\
Its blowing so much coolant into the overflow and the overflow is "overflowing" loosing gobs of coolant.



Thanks guys!

This is the 2 key points in your statement.

Fill your radiator up, leave the cap off.

Now remove all 4 spark plugs.

Let it sit for several hours/over night.

Come back and spin the engine over with the starter.

Watch for water out the spark plug holes.


With you over flowing the overflow bottle (it really is called an expansion tank)

It sounds like you have compression into the coolant jacket.

 

[Stee420aT]

thank you, i will give that a shot tonight! very helpful!

 

[Stee420aT]

so I bled and flushed the cooling system twice. Thermostat is fine. Car seems to over heat in idle even with both fans running then cool down when I hit the gas. I'm starting to think it could be the water pump...any thoughts?

 

[gorf]

Don't over look the obvious, does your radiator cap hold pressure?

 

[Stee420aT]

yes, it sure does.

 

[CleverDSMusername]

one way i know of to check to see if the water pump does its job is to remove a radiator hose & spin it over (be sure to unplug the distributor to prevent full startup) if you make a big mess underneath the front end of the car then the water pump pumps just fine.

 

[DSM1G90]

It's a DODGE.

Take the T-stat out and drill a .050 hole in the T-stat flange so the system is continually getting rid of "air lock". These T-stats don't have the jiggle valve as some t-stats do and DODGE setups love this condition of 'air lock'.

After doing this small mod, you're overheating problems will suddenly disappear...and this goes for all cars that uses a T-stat without the jiggle valve. I've done this mod with S-10 pickups and similar with the same results after this small mod have had no problems after the fact.

"Air Lock' is when there is a pocket of air below(or behind with vertically mounted units) the T-stat that prevents the coolant from reaching the lower section of the T-stat. Thus the coolant isn't being circulated and will over heat .. and the heat of the coolant will eventually open the T-stat to allow coolant to flow. You poke this small hole in the flange and it rids of this air pocket to allow coolant flow at all times, but the hole is small enough to allow the T-stat to open when needed as normally.

My parents K-car body Aries with the 2.2L used to do the same.

Learned this from a independent mechanic on the T-stat trick since the 2.2L used the vertical mounted procedures for the T-stat, which he called a major design flaw with Dodge's cooling system. with the T-stat mounted higher than the radiator.

To the OP: you might also have a clogged cooling system that needs a major flushout-by removing the radiator and flushing out the gunk that resided in the lower of the radiator. Then, the block needs to be flushed out since you got the t-stat out and radiator.... which included flushing out the heater core.

Water must be clear going out as it is going in. Then you know the system is clean.

 

[DeviantBoost]

rent a pressure tester from a parts store theyre great in diagnosing coolant issues

 

[Stee420aT]

I'm having a hard time understanding where to drill this hole exactly... I would like to try this. I will remove the rad again and do another flush that way as stated above. thanks guys!

 

[Stee420aT]

So I drilled a hole in the tstat flange. I drove the car and it didnt start running hot until after over 30 mins of driving...im pretty sure this fixed it jist need to burp the system, there is still air in it. Never been able to drive it that long.

 

[Stee420aT]

So after drilling the hole into the T stat, I removed the radiator, flushed it. Flushed the motor at the T stat housing, put it all back together and re-burped the system. Same problem, just takes a little longer to go through the coolant. It has a high performance metal head gasket and good compression. I'm lost for ideas. I think my next step is going to be Water pump and performance radiator with high power fan.. thoughts?

 

[gusu]

So after drilling the hole into the T stat, I removed the radiator, flushed it. Flushed the motor at the T stat housing, put it all back together and re-burped the system. Same problem, just takes a little longer to go through the coolant. It has a high performance metal head gasket and good compression. I'm lost for ideas. I think my next step is going to be Water pump and performance radiator with high power fan.. thoughts?

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This is is what I use to "burp" the system. You fill it with coolant and let the car run. Once the t-stat opens the coolant level with drop like a freakin rock so be prepared to have enough extra coolant in the funnel for that. Make sure you DO NOT TURN THE CAR OFF BEFORE THE TSTAT OPENS! After it is open wait for the bubbles to stop coming out then turn off the car.

There is a plunger in there you can stuff down the funnel and you can put the extra coolant back in the bottle.

One thing I would check for is all of the coolant lines that go to places other than the radiator. Such as the lines that go to the throttle body and the ones that go to the heater core. I had a friend squeeze the upper radiator hose while I checked around. I honestly had every single non-radiator hose leaking coolant... yes ALL of them. It did the EXACT same thing as your was doing at it's peak. I honestly thought my water pump had gone out until I noticed there was no coolant on that side of the car. It would bump all of the coolant from those tiny hoses in no time at all. Truthfully I don't remember where all the coolant lines come and go from on the 420a, I wish I could help more but I'd have to see one in person.