98 Suburban temperature question

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by Billy D, Nov 2, 2012.

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  1. Billy D

    Billy D New Member

    I have a 98 which runs real good. It was my father's since new and I bought it from him. I did most of the small fixes and maintenance on the truck, but he has had it at the shop a few times without me knowing what it was in for, and he does not remember much when I ask him questions now about fixes. Anyway, the truck does not get above 160 degrees on the temp gauge. I am betting this is effecting my gas mileage since this thing drinks like a pig. I have gone out and bought a new thermostat to replace the old one which I have not done yet. It also had a radiator leak in the past and has since been replaced, but in the meantime a few tubes of that powder stop leak stuff was dumped in.

    So my question is, has anyone had any of the same symptoms or any ideas on why the low temp? My father does not remember if he ever had the thermostat replaced or not, but if so...I am guessing they went with something very low temp as a replacement?
  2. RayVoy

    RayVoy Active Member 1000 Posts 100 Posts

    Very common for t-stats to wear out, it may be stuck open. I would suggest, the place to start is changing the unit and the coolant as well.
  3. Billy D

    Billy D New Member

    I doubt it is stuck open or closed because it's been like this a while, through the summer and have been in mad NY bumper to bumper traffic and never overheated. I'm going to change it and see how it acts. My father probably took it to some hack mechanic up his block who threw in whatever thermostat he could get his hands on or had kicking around that fit and was probably the 160 degrees unit.
  4. RayVoy

    RayVoy Active Member 1000 Posts 100 Posts

  5. Billy D

    Billy D New Member

    Thanks I just checked that. However, I changed the stat today. I was rusty and hadn't done it in years on any car. All went well and no leaks. Noticed they sold me a rubber ring gasket that was not going to work. The stat itself had a rubber edge like a gasket, so just used sealer and tightened things down and it was all good.

    No back to results. The temp does go up now to about 190 or so but then jumps back down to 150-160 as soon as stat opens. It seems like the radiator keep the coolant very cool. Anyway, the temp goes up now but right back down. I'll leave it alone for now.
  6. RayVoy

    RayVoy Active Member 1000 Posts 100 Posts

    So, apparently no t-stat action with the old one in the engine. Maybe covering part of the rad to reduce air flow might keep the temp more constant.
  7. Billy D

    Billy D New Member

    Yes, was going to cover most of the radiator as the weather gets colder for the winter months. This stat is def working better and at least getting the gauge up to normal temps before the stat opens and the temp drops again. At least I can see an improvement that way. When I'm not so lazy I may drain and flush the system and refill it, but this is not my daily driver, so no rush.

    Thanks to anyone who posted ideas.

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