Coolant is foaming



I drive a 1996 Saturn SL2, 5 speed.

My engine overheating warning light keeps coming on even though the temperature gauge is reading normal and stable. Also – i have recently noticed that there is foam in my coolant. I checked the coolant before driving it one morning and the color still looked pretty green, so I’m guessing that there isn’t oil leaking in from somewhere.

Two questions:

1) Is the foaming coolant something to be concerned about?

2) Is it possible my overheating sensor is working properly and my temperature gauge is not?

Thanks for ANY help/comments.


Not good. Your combustion gasses are blowing through a breech in your headgasket and (1) heating the coolant in the water jacket (2) foaming your coolant.

A compression leakdown test will confirm my suspicion. Saturn engines are known for this.


So the overheating warning light might be true even though the gauge is reading normal?

Also – could this be in anyway related to the following recent work:

  1. Coolant system flush in June 2007
  2. replacement of tensioner and idler pulleys in 2 weeks ago

Thanks for the info. . .


Take it back and complain, only because there is a possibility that there’s still flush in the system that’s foaming. Also, there’s a possibility that the coolant was improperly filled and it’s very low, leaving the gage sensor in an air pocket as well as not sufficiently cooling the engine.

You may get lucky. With this new info, I’m cautiously optimistic.


In re: the coolant system flush –

After it was performed back in June, I didn’t notice any foam, but of course I wasn’t checking it. But in the months since I got the system flushed I have not had any overheating warning lights. The overheating warning didn’t start until DAY the tensioner and idlers had to be replaced (they broke completely and caused my car to basically go nuts).

I will talk to the mechanic about the coolant flush foaming connection, but wanted to get honest opinions before going in there.


I’m now wondering of the belt broke because the water pump had seized. And the pump is still bad. I’m pretty sure that engine uses a timing chain and the pump is driven by the serpentine belt.

I’m also wondering if a new shop is in order.


Is there anyway for me to check by myself if the pump is working or not?

S-belt is fine – they checked it. “recommended” i get it replaced, but then after some prodding they said “if it were my car, i wouldn’t change it – it will probably be fine”

Also – to clarify the warning light – it sometimes will turn on for only short (few seconds) then go off again. Which is why i originally thought it was just a sensor that was acting up.

Hope i don’t have to find a new shop – I thought these guys were pretty trustworthy.

Thanks for your comments – has been extremely helpful.


Sounds to me like the cooling flush had nothing to do with the problem. What sounds like happened is the idler/pulley broke, and belt fell off, causing the engine to overheat. Unfortunately you did not catch the overheating in time, and the head gasket is now blown. Sorry to be the bearer of bad news.


You should get a hydrocarbon test in the reservoir tank to check for exhaust gases in the antifreeze.


If there are exhaust gases in the antifreeze would that be indicative of the blown head gasket? or something else?

I’m pretty nervous – if it’s the head gasket – is it even worth fixing?

Thanks for all the info. . .



Nope. Unless you really like the car and it’s otherwise in good shape.


First, the S series cars RARELY experience a head gasket failure. The only problems that Saturn had with the head that was chronic was the SOHC head had a tendency to crack. The DOHC head was very reliable.

The coolant light can serve up to the three functions. If you have an automatic, if it is on steady it can mean either engine coolant temp over heat or transmission fluid overheat. If it is flashing, it means the coolant level is low. This is the function of a level sensor in the coolant resivoir.

Before I start to tear anything apart, I would do as a previous post suggested and test for combustion gasses in the coolant.

Next, if I may, there is a VERY good website specifically for Saturn owners. It is NOT affiliated with Saturn or General Motors. There are MANY members who have a lot of experience with Saturns and are very willing to share their expertise. It is Select “forums”.

And yes, the S series cars use a timing chain not a timing belt. It is designed to last the life of the car. However if you are not good about regular oil changes or keeping the oil level up where it should be, it won’t.


What type of “flush” did you get. Was it a mechanical flush where the coolant was drained and plain water was flushed through the system, then refilled with coolant or was it a chemical flush, where a chemical is added to the coolant system to dissolve deposits and then flushed out.