Ok, later this week Blacky is going to replace thermostat on 2007 2.4 l HHR.

Can't resist. Going to drill 1/8" bleeder hole. I'll give an honest report on warm-up time and operating temperature.

I'll take a similar drive before and after and see what happens.

No change in coolant mixture (50/50 DEXCOOL and distilled water), although I will drain and refill with fresh coolant.

Original thermostat to be replaced by MOTORAD 180 F standard thermostat.

Obviously, more than one variable is being changed, but we can get a good idea of the effect of 1/8" bleeder hole. Mind you, there will be no check valve jiggle pin.

 

Why? You do realize that the heater hose bypasses the t-stat already, right?

 

The closed loop through heater isn't a shunt around thermostat, which is what I'm after.

I may back off and go with a 1/16" hole, but we'll see.

 

curious - pre-GM SAAB's ('94 and earlier 900's and 99's) had bleeder valves on the thermostat housing which allowed you to fully bleed the cooling system - is that what you're going for or is this for some other purpose?
I've installed bleeders on VW, GM and newer SAAB's - seems to make life easier (run a tube from the bleeder valve (same as on a brake system - drill housing - tap for m5 or m6 threads (depends on valve) wrap male threads with some Teflon tape, screw in firmly and you're done) to the recovery tank - crack valve open with engine running and hot - leave open until no more bubbles and bingo - no air trapped in the cooling system!)

Steve

 

Same idea, but in continuous operation. Any air going through bleeder hole ends up in top header of radiator, and even with the thermostat closed there will be flow through the radiator.

 

Have done th i s very thing for air bleeding...only thing is...it took forever to warm up because the water never sat long enuf to heat up..not this vehicle though....so what id do now is take half an aspirin to hold open the t stat long enough to fill system up...

 

Why bother to do this?

Back in the day, there were some advantages to doing this with big blocks, but it was only because it helped alleviate some other issues.

I am going to assume that you have no heating or cooling issues with your HHR, so why fix it if it isn't broke? Is it really worth messing with something, just for the possibility of your HHR MAYBE heating up and throwing heat one or two minutes earlier?

Sometimes messing with something just for the sake of doing it, is a bad idea

 

Hmmm. Blacky says he will give a report on warm up time and operating temps.
Well, what happens if that "hole" in the T-stat gives you the ----- readout on the instrument panel? How ya gonna know what the temp is?

I'm with the others. Why try to fix something that ain't broke?

 

Honestly I don't think it's worth the time, you're not correcting a problem because one doesn't exist.

When it starts throwing codes and setting a CEL, or running like garbage, just remember that "we told you so".

These beasts are not like the vehicles of old, some of us who have reached a "certain age" have found ourselves adapting to the brave new world of sensors on top of sensors, modules for everything, and diagnostic trees that look like alphabet soup.

 

Well, some very helpful comments. To be honest, I'm now convinced that if I only had one shot, no going back - no drilling.

If someone that has modified a thermostat with a bleeder hole can chime in, that would be great. There is no doubt that with the flow coming straight into the hole, as opposed to turning a corner around the open valve of a thermostat, there can be a surprising flow through an 1/8" hole. 1/16" yields 1/4 the area.

To answer a previous question, there are no cooling problems on this car. The reason I am changing the thermostat is age and use.

What would I do if the proposed 1/8" hole upset the computer? Well, if in my judgment the car was warming up fast enough, and assuming no untoward consequences, I'd probably get my jollies pissing off the computer as much as possible. I might go so far as install my own temperature gauge, use black electrical tape to block unwanted visual distractions, and hunt down any audible alarms with a pair of dikes.

Does anyone know HOW the computer decides if the engine is slow to warm up? I mean, consider an ambient temperature of -50 F v. 120 F. Or slow streets v. immediate highway speeds.