Overheating Radiator cap Vs Surge cap (in error)
 

I just found this out the hard way. 2006 models have a "surge tank" other years have the overflow bottle. The Pressure Caps LOOK the same, but are not! The caps marked "Surge Tank" only allow pressure escape, whereas the "Radiator" caps allow for suction from the overflow tank.

When you purchase a new pressure cap, or if you have had service done, or have a used HHR make sure that it is labelled correctly for your car. If you put a "Surge Tank" cap on instead of the "Radiator" cap the hot coolant will go into the overflow tank and never return upon cooling down, thus causing an air bubble in the cooling system and hoses collapsing etc.

Many parts books/counter guys do not make a distinction, and sometimes the wrong part finds it's way into the box.

:twothumbs: Excellent point of reference for folks out there Don, the '06's have some significant differences from the following model years, that's one of them.

I like to think of the '06's as Phase I.

The '07's are Phase II.

The '08's are Phase IIa.

The '09's though the '11's are Phase III.

All HHR's aren't alike, what holds true for one model year doesn't necessarily hold true for others, and in keeping with GM tradition...the owners of the first model year units are "Development Drivers" for those units produced in the subsequent years.

And unfortunately the parts books don't know the actual difference. The ""pressure cap" that I ordered was for a 2008 HHR LT 2.2L, so I ASSuMed that's what I would get. I did notice the "Surge Tank" printed on the cap, but thought "maybe they are the same thing".....WRONG. It only got over 220F a couple of times before I noticed the collapsed radiator hose, thankfully I was watching the temp and turned the A/C on before damage was done. (turning the A/C on turns the cooling fan on).

And then to add to confusion, there is no "radiator cap", it's in the upper hose. So what should "Joe" call it at the parts store?

"Joe" at the parts store is too tied up trying to find a "710" cap for the buxom blond at the parts counter to care.:D

I assume that a surge tank has a pressurized screw on cap, whereas the overflow bottle has the dinky flip cap?

No, they are the same.

I used to say they were different, but have changed my mind.

They are both 15 PSI pressure caps. Surge tank caps let air in and out. Radiator caps let coolant in and out.

It turns out, three years ago, my problem was a blown head gasket.

Don are you sure about this???

I just checked my HHR, a 2006 2.4 ltr., and it says nothing about a "surge cap" on the cap. Not saying it does not take a different cap than other HHR's, just mentioning it does not say surge. Even the OM uses the term, pressure cap, in all of the cooling discussion covered.

Never changed the cap and ordered the car new....so it came from the factory with that cap, and it is part #15042975.

Oh, just thought you make be speaking about a 2.2 ltr. Or is that what you are correcting in the above post?

That's what I'm saying; they are the same! I started this thread 3 years ago, I am now more educated.

It seems that they made a lot of pressure caps in 2006, every store I've looked in had "surge tank" caps. I once got a "radiator" cap and tested it, they are identical except for the printing on the top.

The collapsed rad hose I had was from exhaust gas in the coolant and a clogged overflow hose.


I was "wwwwwwwwr-ng".