Does any one know the manufacturer of the O.E thermostat for the cooling system and thier part #.
No idea as to the OEM manufacturer, but these are the same thermostats are as also used in small block Chevy V-8's. I just replaced mine with a "Mr. Gasket" brand high flow racing thermostat in 165 degree temp range - engine now runs nice and cool, much better than with the OEM one, with a cost to me of $7.99. Highly recommended - no reason to muck about with the OEM one if a replacement is due! What's your GTSi's serial number / month? Cheers - Dave / also a 80 GTSi / 33589 / Sept. 1980
The Chevy thermostat better have the lower by-pass on it or you will cause engine damage . This is clearly printed in the factory repair manual.
Most thermostats have a small hole-water bypass on them. Just make sure you're putting it in the right way. Dave80gtsi, I've never heard of anyone using a 165 deg thermo on a normally aspirated engine. All engines should have a 180 deg thermo. The only reason to use something cooler would be 1) Turbo application (lowering the operating temp will allow you to run higher boost and reduce the chance of knock/predetonation) or 2) Race application. Do you run your car at track days quite a bit? Either way a 180 deg should be fine for daily use and some track day events. And yes this is the pot calling the kettle black. I have a 160 deg thermo in my turbo car. It runs perfectly fine and I like the fact that my under the hood temp is lower, helping to prolong the life of the wiring and rubber under there. Not to mention the paint on the hood. Good find on the replacement application.
The bypass that Slewman is refering to is not a small hole in the thermostat, but a spring loaded plate on the end of the thermostat. The thermostat housing has a bypass pasage built into it. When the engine is cold and the thermostat is closed, the coolant circulates through this passage, bypassing the radiator. When the engine reaches operating temperature, thermostat is fully opened, and a spring loaded plate built into the back of the thermosat blocks this passage off. If this passage is not blocked off, all of the coolant flow is not forced through the radiator, some of it will bypass the radiator and just keeps getting hotter and hotter. Look at the workshop manual, there is a good diagram of the coolant flow through the system in it. A Chevy thermostat does not have this plate. If you install one it will not close off the bypass, and will cause the engine to run hot. Do yourself a favor and get the correct thermostat. Brian Brown Patrick Ottis Company
Hmmm .... Veeeerrry Interesting! The only comment that I can offer in reply is that I personally did the Chevy thermostat swap a year ago, and ever since it has run nice and cool in all kinds of hot weather, even with the A/C on. Using the OEM Vague-Liar temp gauge as the inaccurate reference, it never shows any tendency to run hot. The "racing" description keys off of the size of the coolant opening. I figured that if the thermostat was good enough to cool a high HP Chevy racing engine, it'd have no problems with a lil' ol' stock 3-liter. You can buy these Chevy thermostats lots of places - look for a hot rod shop - I used Jeg's. Available off the shelf in 165, 180, or 195 degree ratings - select your favorite. Cheers - DM / Ohio
Fascinating. The things that you learn on this site! Prompted by this topic, I went into my 'you-might-need-this-someday' box of old removed parts and pulled out the original thermostat. First off, here's the printing on the thermostat, as near as I can make it out: Savara 9.1U.358.00 RRevettata 75.4F I wonder if the "75" above is meant to indicate 75 degrees Centigrade (167 degrees F)? The old thermostat does include a bottom portion which the infamous Chevy one did not. See enclosed pictures which show the unit 1) at a cold state, and 2) after it has been dunked in a pan of boiling water to open it. This bottom valve does indeed appear to serve the function of blanking a passageway in the thermostat housing when it is in 'open' condition. So, maybe the replacement Chevy idea is starting to lose some of its appeal. Why didn't I notice this obvious difference at the time? However, the bigger question remains ... I have been using the Chevy one for a year, in all kinds of hot and cold weather, and the car runs notably cooler with it installed than it did with this old thermostat. Thus, I conclude that the Chevy one has not been blanking off the 'mystery' passage, yet the engine seems to operate just fine with this passage open. The drawing of this housing in my workshop manual which supposedly shows this area is not as clear as I think it ought to be. Can anyone post a drawing / picture which shows this portion of the t-stat housing, and exactly what happens when the mythical passage is left open? Thanks and Cheers - DM / Ohio
The problem with not having the bypass passage blocked off usually causes the engine to overheat when you are idling in stopped traffic on a hot day. Can you have your car idling for a 1/2 hour on a 90 deg. day without it overheating? Even though the fans come on and cool the coolant in the radiator, the coolant that is bypassing the radiator just keeps getting hotter. At low rpms the waterpump does not provide much flow. The coolant flow will take the path of least resistance, so if the bypass is open it will go through the bypass rather than all the way up to the radiator and back. I have seen this problem numerous times on 308's and 246's Brian Brown Patrick Ottis Co.
