Expansion Tank Boiling Over

[elgato]

I posted this in an old thread in the General area but did not get a response.

2002 3.5 98,000 miles.

Often the display will show coolant low even when it is at the proper level. The gauge appears to be in the normal range. After driving about 10 miles in the heat and stopping the expansion tank will be boiling over. The car does not appear to be overheated but the expansion tank is boiling like crazy.
No external leaks.
No water in the oil.
No white smoke at the exhaust.
Fans appear to be working fine.

I have not seen it happen at a long idle, just after a long drive in the 100 degree heat.

The cap was original GM and obviously the seals were failing. I replaced it with an Autozone 18lb and now instead of just spraying out around the edges it snaps open with a loud pop.

I borrowed the block test kit from Autozone and the fluid stayed blue. If it is a head gasket leak it only opens up after a long drive.

A mechanic suggested that a thermostat stuck half closed might cause these symptoms.

Just start throwing parts at it?

THanks

[tvthegreat]

Sounds like you may have a couple different issues going on at once. I would replace the cap with a AC Delco one, replace the thermostat & water pump. The overflow tank has a build in level sensor that typically go bad & it will give false readings on the DIC, if you are getting that. More than likely the thermostat is bad & not opening at the proper temperature, which in-turn allows your boil-over issue. Some parts I will not use other than AC Delco, one is the coolant cap. Others include any engine/transmission sensors, fuel cap & most electronics. My guess, based off your diagnosis, that the head/intake gaskets are fine.
Good luck!
Troy

[elgato]

Thanks for the response.

Its 100 degrees here today.

I just let it idle for 15 minutes and then drove for another 15.

The gauge stayed right at half. It showed no problems whatsoever.

Did the block/gasket test with it off and running and the fluid stayed blue.

So hard to diagnose when it will not fail.

I did notice that the gauge moves to about the 3/4 point when the overflow occurs.

The only thing that would be this intermittent would be a sticky thermostat ?

Where do you guys buy Olds parts locally?

What other cars have this 3.5?

Thanks again.

[tigger]

Aug 31, 2015 16:13:18 GMT -6 elgato said:

The only thing that would be this intermittent would be a sticky thermostat ?

Where do you guys buy Olds parts locally?

What other cars have this 3.5?

Thanks again.

1. Good, cheap place to start. And you can refresh your coolant while you're at it...

2. Advance O'Napa Zone carries some Delco parts, pretty hit and miss. RockAuto and Amazon are your friends...

3. '99 and up Olds Intrigue, '01-'02 Olds Aurora 3.5, that's it AFAIK...

[elgato]

The dealers here say that they only sell the housing/thermostat combination.
The car already has the newer housing 12570247.

Online everyone has the thermostat by itself. It looks like it clips into the housing.
Does it just snap in? Any reason to not just buy the thermostat alone?

Anyone trust aftermarket thermostats in this car?

Thanks again.

[tvthegreat]

GM doesn't make all the parts on the car, just like they don't make the tires. So the thermostat, itself, is probably Gates or Goodyear, or something like that. I replaced mine with a Gates, but I have the 4.0 & the 3.5 appears different. If you think the housing assy needs replacement, then go with the assy, but if the housing is fine, just replace the thermostat if it is separate.
I just copied & pasted your part number into Amazon, here is the link.....

www.amazon.com/ACDelco-15-10571-Original-Equipment-Thermostat/dp/B000EQN1H4/ref=sr_1_1?ie=UTF8&qid=1441153643&sr=8-1&keywords=12570247

80% of the parts I purchase is thru Amazon, other 20% would be used parts or if I need something right away, Napa, Car-quest, Orileys, GM dealership, ect. Rockauto alot of times is cheaper, but with the shipping, makes it more expensive. I have the Prime account with Amazon, so I get free 2 day shipping. The nice thing about Amazon, is their rating system. You can see if others bought the part & if they had any problems. You don't get that thru Rockauto or Napa. For instance, the link I supplied there was 1 person who left feedback & they gave it 5 stars with a long description of overheating on a Olds 3.5. Some parts I buy used, some only new. A thermostat I would never go used, but I needed to replace my battery & bought one at a local salvage yard for $25 & they gave me a 90 day warranty. I just replaced the struts & they were $72 each on Amazon & free shipping. These were quick struts, which already have the spring & top bearing attached. No way GM or Napa could touch that price. There was loads of feedback & ratings & decided to go with those based on the feedback & ratings from others that had purchased the same part.


Here is the link for the struts I purchased....
www.amazon.com/FCS-1332343-Complete-Strut-Assembly/dp/B008X02RK0/ref=sr_1_1?ie=UTF8&qid=1441155241&sr=8-1&keywords=FCS+1332343

Some parts you really don't have a choice, you have to buy at a dealership, but those are few & far between. Good luck.
Troy

[elgato]

Does the belt have to come off to replace the thermostat or is there enough clearance to slide it out?

FYI

All that is necessary is to loosen the belt and pull it off the top pulley to get some slack. No

need to completely remove it.

[elgato]

Pulled the thermostat today. It does look like it was sticking.

Here is a picture of whatever was in the car next to the new AC Delco.

[elgato]

It now has a new GM Thermostat and Cap. It does run a little cooler than before. The gauge stays at right at the half way mark.

Today with it fully warmed up and idling the coolant in the tank was bubbling like crazy. There was a bit of seepage around the cap.

Is this normal behavior?

After it cools the coolant settles back down to the full line.

[tvthegreat]

There is a difference between bubbling over & boiling over. If its boiling over (overheating) its probably a cooling issue, water pump, thermostat, blocked coolant line, radiator, fans, ect. If its bubbling over, its probably a head gasket. In your first thread, you stated boiling, so that's what pointed to the thermostat & cap. Now in your last post, you talk about bubbling. If its boiling over after replacing the thermostat, I would make sure the system is burped properly & inspect the radiator closely. If its bubbling, it is possibly due to pressure from the combustion chamber being relieved into the cooling system through the leak in the head gasket.
I don't think either is normal behavior.

[elgato]

I know you guys can only guess without actually seeing the problem. I appreciate your time and effort.
Honestly in a closed plastic pressure tank its hard to tell if its boiling or bubbling.

Today with the coolant right at the full line I let it idle for about 20 minutes with the cap off. Temperature gauge never passed 50%.

Eventually the coolant level began to rise. When it was about 3/4 full it began to bubble from the main tube at the bottom. You could see a lot of air bubbling up from this tube.
While it was doing this I tested it several times with the Block Tester. The fluid stayed blue. Soon it reached the full point and coolant began pouring out. When there was room I did another test. Still Blue. Turned off the car and tested again. Still blue.

I would think that if the bubbles were exhaust from a head gasket leak the tester would see it. Going to talk to another mechanic today.

What a nightmare.

Thanks again.

[elgato]

Another update:

Put a pressure tester on it this afternoon. Could not get any pressure at all. At first I thought I was just not getting a good seal at the tank. When I twisted the tester connection to remove it the brass neck came out with it. There was corrosion all around the base AND there was a crack on the side. So all the symptoms of a bad cap were actually the bad brass tank neck.
I am guessing that a new tank that holds pressure should stop the bubbling coolant problem.

[RCA1186]

Never could have guessed that, mostly because the Classic doesn't have a brass neck, all plastic . Good find!

[elgato]

Put in a new Dorman expansion tank. $60 at Amazon vs $120 at Autozone.

Drove it for quite a while yesterday in the heat of the day. Seems happy as a kitten.

Amazing how this car will boil over with any loss of pressure.

Hate the design with the expansion tank under pressure. The old standard radiator cap with a non pressurized recovery tank was
much more reliable and certainly safer. Where do some of these idiot engineers come from??