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Replacing Thermostat

Discussion in '80-Series Tech' started by bderks, Apr 9, 2003.

  1. bderks

    bderks

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    I just replaced the thermostat on my 97 last night, and thought I'd make life easier for anyone needing to do this repair by doing a writeup. Being the "F it up and learn" type of guy, I thought I'd save you the pains of my mistakes and tell you the right way to do it the first time.

    Be sure to get the OEM thermostat. I bought OEM and an aftermarket one, and the difference in quality is huge.

    Tools needed: new thermostat, gasket, wheel ramps, 12mm socket w/ long extension, 12mm small box wrench (or rachet wrench), small funnell with about 2 ft of flexible tubing, a clean bucket with about 3 gallon capacity, shop rags, plentiful #6's on ice.

    First off, get some wheel ramps. This will make the process much easier, as you have to crawl underneath to remove a protective bracket and the radiator drain plug.

    First step is to remove the bracket below the radiator with a 12mm socket, this will make accessing the plug much easier. You may have to remove the 2 bolts that hold the steering stabilizer in place as well to get the bracket completely off. I elected not to do this, and instead just rotated the bracket out of the way.

    Locate the white drain plug, which is on the bottom left if you are underneath looking up. Position the small funnel as close as you can below the plug (hold in place with some bailing wire, etc), attach the plastic hose to the bottom, and place the hose in the bucket. Why use the funnel? One, the coolant will NOT come out the hole in the frame it's supposed to, instead spewing all over the damn place like a 16 old girl after drinking 4 liters of Purple Passion on prom night. Two, if you're planning on reusing your coolant as I was (brand new) this will keep it from becoming contaminated after touching every dirty/greasy object on the way down.

    Now once you have everything positioned properly, remove the bottom drain plug. THEN remove the radiator cap slowly, but don't take it all of the way off. This will allow the coolant to drain, but not come out too fast and make a huge mess.

    Once the radiator is fully drained, it's time to remove the thermostat. Looking down at the engine from the hood, follow the hose from the bottom left to the thermostat housing on the engine, it looks like a triangular piece that swallowed a golf ball, held on by 3 bolts. The bolts on the housing are a real hoot to get at.

    First remove the front half of the heat shield from the exhaust manifold with a 12mm socket. Then get your 12mm box wrench out and remove the thermostat housing. This would be a great place to have a ratchet wrench, as the bottom left bolt is a bitch to get at. Replace the thermostat and gasket, be sure the gasket is properly seated.

    Replace the housing, being careful not to overtighten the bolts. Replace the heat shield. Replace the radiator plug, refill the radiator, and replace cap. Replace the bottom bracket. Start the engine and make sure there are no leaks, let run for a minute, then check the coolant level, refill as necessary.

    If you did it the way I did the next step is to throw faulty thermostat at wall because you're pissed that you were too lazy to buy a funnel and now have a red coolant pond covering the garage floor.
    :stupid:

    Next tutorial: patching small holes in drywall. ::)
     
  2. CDN_Cruiser

    CDN_Cruiser

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    Thanks man - very helpful. How did you know your thermostat was shot? I found that my heater seemed to be quite cool over the winter and I was thinking it could be the thermostat.

    Cheers, Hugh
     
  3. Photoman

    Photoman SILVER Star

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    Just one little thing to add. Make sure the jiggle valve on the thermostat is straight up or between the 11 and 1 o'clock positions.
    Bill
     
  4. bderks

    bderks

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    I noticed that my LC would not heat up as quickly (if at all), so I figured that the thermostat was stuck in the open position, therefore always letting coolant circulate.

    If your vehicle is warming up to normal temp but you're still not getting much out of the heater, it's probably not the thermostat. Not sure what that would be - I'm sure CDan or B could give you a lengthy dissertation though! :G :G
     
  5. Beowulf

    Beowulf

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    bderks,
    Others should take note that the thermostat does not come with a new gasket so be sure you buy one. One more addition that might be obvious to some but was not to me.  :ugh:   The gasket has a groove and it goes *around* the new thermostat.

    Did this fix your heating problem?
    -B-
     
  6. bderks

    bderks

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    I was wondering about that little thing - what exactly does the jiggle valve do? Luckily I noted it's placement and put the new one in accordingly.

    Jiggle Valve sounds like something a mechanic would try to sell you:

    "We replaced your muffler bearing and jiggle valve, and topped off the halogen fluid in your left headlight"
     
  7. bderks

    bderks

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    B - great points, the only reason I knew about the gasket was your post on SOR.

    Yes, my heating up problem has now been solved. It now heats up in about half the time that is ever has since I bought her a year ago, so it seems the thermostat has been going out for quite awhile.
     
  8. cruiserdan

    cruiserdan SupportingVendor Emeritus Supporting Vendor Moderator

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    The jiggle pin allows equalization accross the thermostat while the cooling system fills. Put it at the bottom and you get an air pocket.
     
  9. CDN_Cruiser

    CDN_Cruiser

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    BD

    What was the rad gauge reading before you replaced - low or mid?
     
  10. bderks

    bderks

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    CDN_Cruiser - The Temp Gauge would barely get above C when the weather was cold, and about a quarter of the way up when the weather was 50 degrees F or above. That's about 9 degrees C for those of you North of da Border... :G