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Discussion Starter #1
I'm getting pretty frustrated. I have to burp my coolant about every 50 miles because my radiator seems to be getting filled with air. Before I go out and buy a new thermo, I wanted to ask here if there can be other reasons for air filling the cooling system. If I fill my reservoir (plastic overflow tank), it just goes dry eventually anyways. I think it is sucking air in through there, but since my temperature is fluctuating eratically-- even with a full radiator, I am blaming my thermostat.

Anybody have any ideas?

PJ
 

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i'm sure you've checked all the hoses and what not, but a buddy of mine had this happen and it was his heater hose letting air into the system, also have the radiator pressure tested and see if it leaks any where

--Dan
 

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Mine does the same thing, I found that the radiator is leaking at the trans cooler fittings, just enough to suck in some air and make my temp guage go back and forth.
 

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Discussion Starter #4
Thanks for the replies. I am going to check the hoses today. I don't think it's the radiator itself since it is relatively new. Wouldn't it leak coolant too when it gets hot, though??

PJ
 

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On mine I guess that its either sealing up when hot due to the plastic expanding, or its still leaking but steaming off before it drips. I would never see it leaking when running or hot, but wherever I park it to cool down is where I see the little puddle of coolant. Its parked now until I can fix it.
BTW, when I got my car, the radiator was in the trunk covered in other engine parts. I didnt expect it to be too good anyway.
 

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Discussion Starter #6
Well, it wasn't the heater hoses. I replaced them in case, but nothing.

I'm hoping it's not the radiator, but I am hoping it's nothing in the engine either. Will a pressure test conclusively spot the problem?

PJ
 

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I'm wondering if there may be a small leak in someplace 'hidden' - such as the pressure relief cap/reservoir cap, vent plug (if there is one), or even the water pump.

Here's the pressure test procedure from the 1994 Service Manual:

Cooling System Pressure Test

WARNING:
NEVER REMOVE THE PRESSURE RELIEF CAP OR VENT PLUG UNDER ANY CONDITIONS WHILE THE ENGINE IS OPERATING. FAILURE TO FOLLOW THESE INSTRUCTIONS COULD RESULT IN DAMAGE TO THE COOLING SYSTEM OR ENGINE AND/OR PERSONAL INJURY. TO AVOID HAVING SCALDING HOT COOLANT OR STEAM BLOW OUT OF THE RADIATOR OR VENT, USE EXTREME CARE WHEN REMOVING THE PRESSURE RELIEF CAP OR VENT PLUG FROM THE VEHICLE. WAIT UNTIL THE ENGINE HAS COOLED.THEN WRAP A THICK CLOTH AROUND THE PRESSURE RELIEF CAP AND TURN IT SLOWLY TO THE FIRST STOP. STEP BACK WHILE THE PRESSURE IS RELEASED FROM THE COOLING SYSTEM.WHEN CERTAIN ALL THE PRESSURE HAS BEEN RELEASED, PRESS DOWN ON THE PRESSURE RELIEF CAP (STILL WITH A CLOTH), TURN AND REMOVE IT.

1. Turn the engine OFF.

2. Check engine coolant level as outlined.

3. Disconnect the electrical connector from the water temperature indicator sender unit (10884) and remove the water temperature indicator sender unit from the engine.

With the pressure relief cap radiator cap (8100) installed and the cooling system pressure relieved, only a small amount of coolant will be lost when the water temperature indicator sender unit is removed.

4. Install the adapter fitting from Rotunda Radiator/Heater Core Pressure Tester 021-00012 or equivalent (male thread on one end and hose connector on the other end to accommodate the tester hose) tightly into the intake manifold (9424) or cylinder head (6049) in place of the water temperature indicator sender unit.

5. Disconnect radiator overflow hose (8075) from the radiator (8005). Install a separate hose, making sure hose is firmly installed on the radiator overflow nipple and is in good condition. Insert the free end of the hose into a container of water.

6. Attach the pressure pump and gauge to the adapter fitting and pressurize to the lower limit.

No bubbles should appear in water container. If the system is satisfactory at the lower limit, gradually increase the system pressure until a slight stream of bubbles appears in the water container. This is the upper limit of the pressure relief cap.

Replace any pressure relief cap that exceeds the specified upper limit pressure without discharging bubbles.

7. If the pressure relief cap does not hold pressure, remove and wash the pressure relief cap in clean water to dislodge all foreign particles from the gaskets. Check the sealing surface in the filler neck.

Then inspect the cam lock flanges on both sides of the filler neck for maximum pressure relief cap engagement.

8. Pressurize the cooling system as outlined in Step 6 (using a pressure relief cap that operates within the specified upper and lower pressure limits) and observe the gauge reading for approximately two minutes. Refer to «Specifications» . Pressure should not drop during this time.

RESULTS: If the pressure drops, check for leaks at the engine-to-heater core hoses, engine-to-radiator hoses, bypass hose, water valve hose (if applicable), water outlet connection gasket, radiator and heater core, etc. Also refer to engine system checks if a leak cannot be located in cooling system. Any leaks which are found must be corrected and system rechecked.

If the system holds pressure, proceed to Step 9.

9. Release system pressure by loosening the pressure relief cap and remove the adapter. Install the water temperature indicator sender unit, check coolant level and replenish if necessary with the correct coolant solution.
 

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Could be the heater core... I know you probably never use the heat but there's still coolant circulating through there. I never even thought about it until we had a cold night and I turned on the defroster and got steam on the windows. Bypass it and see if your troubles go away.
 

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I hope this is not it, but do a search on "head gaskets"

I wish you better luck than I had with these same symptoms.

Take care
Darrin
 

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Discussion Starter #11
To burp the system, you open the radiator cap halfway-- but be careful not to burn yourself.

I got the car pressure tested, found a bad hose clamp, so I replaced that. My radiator cap only held 13 lbs, so I replaced that (supposed to hold 16 lbs.). The system holds pressure now, which is good, but I think I need to replace my thermostat. It runs in acceptable temperature ranges, but I feel the thermostat is a little sticky.

Thanks for the help, guys.

PJ
 
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