I just got my new radiator in on my '98' Saturn SL2. In attempting to add the coolant I filled the main resevoir and I expected it to drain down into the radiator. It didn't, except for a small amount. I let the engine run briefly but didn't want to continue in case there was very little coolant was in there. I replaced the cap on the resevoir, started the engine again and ran it briefly just to see if it would help move the coolant . I shut the engine off and when I removed the resevoir cap the coolant overflowed. Am I being too cautious? There was only about two quarts of coolant at most. The radiator does not have a cap on it. Any suggestions?

 

Someone with S car experience should chime in soon. You probably need to remove a small hose at a high point to let the air out of the system. There is a proper bleed sequence so don't run it until you know it is full of coolant/water mix.

 

No, you are being intelligent.

You must have drained the system pretty well. Did you remove the drain plug in the block?

There is no place at all for the air being displaced inside the block to escape the system (no bleeder) except through the reservoir (which is a pressurized portion of the cooling system when the cap is screwed on tight), the system needs to have ( 1 is ideal)

1) the thermostat open to fill the block and the rest of the system (car at operating temp ish)
2) a sufficient amount of coolant to start with in the block so that you do not toast your engine.

3) In most Saturn S cars if you refill it while still hot, the thermostat stays open, the coolant fills most of the system, and you leave the cap off the reservoir with the engine running to create a vent for the air in the system.
The engine will not overheat in the above described case of you only do it for about 5 min (with the cap off for burping and topping off).

Since you are trying to fill it cold, i suppose you need to get more coolant into the block before you start.

I would try:

1) look up the capacity of your radiator and the reservoir if possible.
2) add that much 50/50 coolant/water, maybe with the rad drain petcock ever so slightly open so that you are sure the rad is filling during this process.
3) CLOSE THE RADIATOR DRAIN VALVE!!!
4) Remove the top radiator hose at the rad (since this is a fresh connection and easy to undo) and fill the block slowly with 50/50 coolant /water
mix. Yes this will introduce air into the system. More importantly for now, it will introduce COOLANT into the system. Go slowly and KEEP TRACK of how much fluid you add before no more coolant can be filled into the block.
5) Reattach the upper rad hose to the the radiator, fill the reservoir to the top,

6) Start car (cold) and run with the reservoir cap OFF.

With coolant in the system and thermostat closed, you should be able to get a reasonably good estimate of coolant temp (in the head) from the temp gauge on the dash. As long as this is not dangerously high you are prob ok. It may bounce around a bit due to the air pockets in the system.

Watch the temp gauge. As it gets near operating temperature, the thermostat will open and should drain the reservoir into the cooling system while at the same time allowing air to escape. Don't let the reservoir run dry or you will be introducing more air in.

7) Keep topping off reservoir with coolant mix until even level at even operating temps and no more air seen escaping at the reservoir.

8) Attach reservoir cap and let it idle. Once pressurized, be sure both upper and lower rad hoses are hot and that temp holds steady = no leaks and thermostat open.

If both hoses to not get warm OR the car starts to read very high temps on the gauge, your thermostat is likely stuck patly closed

 

Is the thermostat in the top or the bottom hose? On the L200 the thermostat is in the bottom hose. L200 also has a bleeder hose from the high point back to the reservoir.

 

Derf, thanks so much for your detailed reply. It is my son in law's car and he had a leaking radiator for quite some time and decided to replace it. I somehow managed to get stuck with the task. Since it was a radiator exchange the radiator was the only thing drained---nothing else. Opened the drain valve on radiator and nothing came out. Removed both upper and lower hoses and got a quart at most. Didn't look into draining the block. So, I suppose there could be a certain amount of coolant remaining in the block otherwise I should expect to see the temperature gauge rise very quickly.

 

Derf, I disconnected the top hose and was able to pour about a quart into the block. Reconnected the hose and started the engine. After about two minutes the ENGINE temperature warning light came on. However, the coolant temperature gauge had not moved much at all. Top radiator hose was warm to the touch and the bottom hose was cold. The hose from the reservoir to the engine was warm. Any recommendations based on this?

 

That light doubles as a high coolant temp light PLUS low coolant LEVEL light.

The coolant level sensor is in the bottom of the overflow tank. I believe it is a pressure based switch that is sensitive to the "head" pressure of the coolant sitting in the expansion reservoir.

Even a slightly low level in that tank will cause that light to flash.
The other cause of that light flashing is that coolant level sensor/switch getting gunked up w sediment and malfunctioning, causing the sensor to trigger falsely.

In your case, if you've never had issues with it AND since you're trying to refill the system, I'm guessing that the level is not quite high enough.

The drop in coolant level could have been from coolant forced into the radiator and the air being vibrated back up into the expansion tank and being replaced w coolant once you started the car. You said that line was warm, so is a possibility.

02 LW300 - the thermostat is indeed at the block where the LOWER radiator hose attaches.

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Get the reservoir up to the full line with the car cool. Start it and let it run w the cap off. If the light is flashing immediately, there may now be an issue with the coolant level sensor. We'll tackle that if we have to.


Water pump "pulls" coolant through engine out the top through top rad hose, through rad, gets cooled by passing air while driving and fan if needed.
Cooled off (somewhat) coolant exits bottom of radiator , goes through lower rad hose through/around thermostat while entering at bottom of the engine. (Heater hose path not included for simplicity).

The bottom hose being cool means the thermostat has not yet opened -- the circulation of warm coolant from the block thru the rad at the top and out the bottom has not begun. I don't think 2 min is long enough to get the engine up to 185 (?).

IMPT: How long did you run the engine with the cap on the very first time you filled it when it boiled over at cap removal?

2 min is not long enough to get an S car engine up to the temp that would open the thermostat. Bur a closed system (cap ON) with very little volume all locked in rad volume + reservoir vol + heat radiating through warm coolant not moving AND there not being enough coolant allowing the engine to heat quickly would INDEED probably boil over after you released the pressure on the system.

The common theme: The thermostat was not yet open.
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If your dash temp gauge is behaving somewhat like it did when the cooling system was fine before all of this in terms of how long it took the temp gauge to rise, I'd cautiously let it warm with the tank cap off and continue to warm, alternating between driver's seat and reservoir tank.

Note that the coolant temp sensor is IDENTICAL to the air intake temp sensor, so reliable readings are given whether it is submerged in coolant is surrounded by air. If the gauge is flying up at a crazy rate, turn the key off. If the gauge is acting normally, it's probably ok.

Once the thermostat opens, the level in the reservoir will drop so be there at the tank w your 50 50 mix. The low coolant light should blink but you'll know why. Keep topping it off.

If your thermostat was stuck closed, I'd think you would have had rapid overheating issues prior to ever swapping radiators.
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Addl options: Do BOTH or NETHER for now

1) Draining and keeping the new coolant mix from the rad and the block and replacing the thermostat. Takes possible failed thermostat possibility out of the equation. Get a standt thermostat. The thing is 19 yrs old. Mine's 20.

2) Drain and remove the coolant expansion tank and keep the hose to it above the level of the rad to prevent further coolant loss. Rinse it out w plain water and see how much sediment was in there, unless you poured it out with the coolant.

Put a TINY TINY TINY amount of dawn dishwashing liquid in the reservoir after filling 1/3 w hot water. Fill the reservoir to 2/3 with more hot water SLOOWWWWLY to keep from making 3 billion soap bubbles. Covering the opening with 2 or 3 thick clean wastable actual towels, not paper towels, agitate to distribute soap and let soak for 5-10 min {I don't put the lid back on b c I don't want the soap residue to get stuck in the pressure release mechanism.).

Give it a good but gentle agitating an then rinse until there are no more soup bubbles in there. Don't want suds in your cooling system. RINSE RINSE RINSE.

(Oh, or you can by an aftermarket reservoir w integral sensor. They work fine too. You just can't get the sensor alone.)

By doing these two things, you're taking the thermostat and hopefully a potentially fubarred coolant level sensor out of the equation.
Neither is necessarily bad. This is NOT my preferred method of "troubleshooting" (= shotgunning parts) but the thermostat IS 19 yrs old and if you do that you might as well take advantage of the fact that the cooling system is open to clean the tank sensor.

Entirely your call.

Just trying to put the options out on the table and overexplain them as bloatedly as possible because you're still reading at this point whereas most of the regulars on the forum stop reading my "novels" half way through.

Please keep us informed and don't trash your engine

 

I read the whole thing Derf! Keep us posted.

 

I really appreciate the help. Weekend is a loss for doing anything with the car but I will get back at it on Monday. One thing though, the light does not come on immediately. It comes on a couple of minutes after I run the engine and I immediately turn it off. I'll get back to you. Thanks!

 

I had a 95 SC2 that would do that in the winter only.
I've always assumed that it has something to do with thermal expansion and contraction of both the coolant fluid and the tank and hoses and.....

Starts fine, runs fine. 2 min later the low coolant level light blinks for about 30 sec. Temp gauge has barely moved. After about 30 seconds of blinking while driving normally, the light stops blinking and good karma is restored.

My back of the envelope explanation to myself is that

1) everything same ice cold temp
2) start engine. water pump has nowhere to move the coolant to b /c thermostat is closed, so keeps pushing into rad, which warms up coolant in rad, which eventually warms up coolant in expans reservoir. However, my only logical guess from this all is that the reservoir starts to expand when the warm coolant comes in, and the reservoir expands more than the coolant in it. This creates an "expansion tank not 100% full" situation, and on comes the light.

As soon as the rate of expansion of the coolant overtakes the rate of expansion of the reservoir, the sensor goes off.

This behavior was absent the first 19 years I owned the car. Does it every winter like clockwork. I even replaced the reservoir/sensor combo and did a coolant change --- and it behaves exactly the same. My 97 SC2 has gotten to 20 years old without doing it so far.

As far as I am concerned, it is a harmless evil case scenario of a bunch of factors that happen for 30 seconds and are done.