'95 GMC Vandura Explorer Poor MPG

Discussion in 'Performance & Fuel' started by ScandiHooligan, May 1, 2010.

  1. ScandiHooligan

    ScandiHooligan New Member

    I've had this van for 9 years now. Bought it in '01 in very nice condition, (dealership serviced regularly) with 75, 000 miles on it. It now is still in very nice condition, (garage kept) has 135,000 miles. About 4 years ago I had a local shop, (I live in Florida) do some A/C work, (new compressor and hp line). The mechanic told me, (I know the guy) he also replaced the fan clutch with a heavier duty clutch and I don't remember if he told me this or it's just my suspicion, (temp indicator doesn't move much off of 100 degrees. Could be the gage?) that he also removed the thermostat. Ever since then, the van went from about 14 mpg to 10 mpg local and highway, A/C on or off. Now needless to say, with gas prices what they are, we don't drive this van around very much anyway, unless we need to, but I like it, I own it and I like to drive it. I've recently decided to try and get to the bottom of this poor MPG issue. I read on this forum a comment from one of the guys that, (and I'm paraphrasing here) "if things get worse after you've replaced a component, go back to that component". Makes sense! I've researched this forum and others to try and find out whether it would be better to go back to an OEM fan clutch, (the one my mechanic installed was a Hayden Severe Duty Clutch) or if I should consider going with electric fans. I can't say I've come away from any forum with a definite conclusion. I called Hayden Tech Support and asked for their advice. Pretty much the same. Flex-a-lite hasn't returned my call yet. My feeling is to replace the Hayden Severe Duty Clutch with their OEM version, (being the cheaper thing to do) reinstall, if it's missing the thermostat, (thinking that could be messing with the ECM?) and see what happens to the MPG then. If I still have an issue, I'll then have to look else where.

    Any comments or suggestions with regards to this issue and electric fans, would be very appreciated. I want to squeeze as may MPG out of this thing as I can. I'm already running Amsoil in the engine and the differential.
    Last edited: May 1, 2010
  2. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    If I'm reading correctly the mechanic removed the thermostat, in newer vehicles this can cause poor mileage. The coolant runs through the engine so fast that it never cools down properly and the temp sensor keeps things running as if the engine is still warming up, this in turn makes the vehicle run rich.
    An electric fan will improve mileage and performance slightly.
    The first step I'd take is to isolate the reason the vehicle had suspected inaccurate temp readings.
    Next replace the thermostat.
    Then replace the fan with an electric fan system.
    You dont especially need a FLex A Light fan (although they are one of the most complete and easy to install kits sold) you could use an off brand fan or do a Ford Taurus fan conversion (Google ford taurus fan conversions) and get the same results at a possibly better price.
    I dont think the Heavy Duty Clutch fan caused your issue, the heavy duty unit has a larger revolving mass but uses the same size fan, resulting in almost the same resistance.
  3. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

  4. ScandiHooligan

    ScandiHooligan New Member

    Another reason I believe the mechanic removed the thermostat is that, in the winter, (Florida winter that is) the van heater never gets hot. The best I get is luke warm; not enough to warm you up inside. Thanks for the info on the Severe Duty Clutch. I've already purchased a Hayden OEM clutch, but it's still in the box, so I can return it. I'll check the Thermostat first and either install one or replace it as the case may be, then see what the MPG does. I'm on the road right now, so it will be about a week before I can work on it. Thanks also for the info on the Taurus Fan. I did read the thread in this forum yesterday about the conversion, but I'll do the google search as well.
  5. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    With out the thermostat the motor will not get warm enough for the heat to get warm.. You will need to install a 195 Degree T-stat. Also you will want to look into the heater core.. There might be scalling building up, and it might be time for a rebuild.. I live in MN and if you remove the T-stat you wont have heat during the winter... Most likely your T-stat was stuck open.. So simply putting a proper temp one in you might fix all of your issues...
  6. chevygurl

    chevygurl Rockstar

    I definitely think you should install a t-stat. I also live in FL; just get one with a different temp, like murdog suggested.

    How many miles does it have on it now? The catalytic converters went out on my Dad's '97 around 90,000 and KILLED his MPG- he was getting similar to you: about 14-15, then went down to 8 or 9 (He's got the V8). His was running rich because the converters weren't sending the right info. His is obviously an OBD-II, where yours is an OBD-I, but that could still be your problem if the t-stat doesn't solve it.
  7. ScandiHooligan

    ScandiHooligan New Member

    I finally got home again last weekend and had the time to check on the thermo. It was there, but it was stuck open. Put in a new 195* . A friend of mine has a Transmission shop. It hasn't been serviced for a while, I told him about the MPG issue, so he said he'd give it a good looking over and make sure everything is doing what it's suppose to. Hoping to do that this week. Let you know!
  8. ScandiHooligan

    ScandiHooligan New Member

    My van has 136,000 miles. Hadn't thought about the Cat. Converter. I would have assumed the "Check Engine" light would have come on? How do you actually go about checking the converter?
  9. dualdj1

    dualdj1 Rockstar 100 Posts

    At the very least you want to have some resistance in your coolant flow, such as a thermostat with the center valve removed, so the coolant won't flow too fast. However as the other said, even in FL you want to have a stat installed. The only reason not to have one would be summer and running too hot, not winter/too cold.
  10. ScandiHooligan

    ScandiHooligan New Member

    Got it back from the Trans shop about 2 weeks ago. The Torque Converter had apparently failed to some degree, which caused the O/D to fail. I never noticed a shifting issue. If I'd had a tach I would have had a reference point. Think I'll install one and a Vac guage as well. Anyway, I only had a chance to run through one tank of gas which was a combo of local and a little bit of highway driving. My mileage increased to 12 mpg. I still think I should be able to get a little better than that. I'm also running Amsoil 10w/30 in the engine and Amsoil gear oil in the rear.

    So to sum it up:

    Thermostat is fixed. Tranny is fixed. What would be the next reasonable component to investigate? Cat Converter? How do you check that? O2 Sensor?


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