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Pat K

1985 gas tank?

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I have vapor locked twice twice going up the same hill, same place, hot day. After the first time, I took care of the overheating problem with a new radiator. So, I was quite surprised yesterday when the car did it again, about the same place but the temp gauge was just a little over 200. So, I am guessing fuel pump and I would like to make it electric. My mech asked me do I have a camaro gas tank, therefore camaro fuel pump, or something else?

I gave him my usual "huh?" expression.

Any ideas?

PK

RQB 4143

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No, really not even close to a Camaro fuel tank. Your '85 still has the same basic tank that Studebaker used in their first '63 Avanti. If I were you, I'd first work on getting that engine temp down a bit.

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I would love to get the engine temp down a bit. Last summer, hot days would push the engine temp to 220, at which I stopped driving it. Replaced original radiator this spring and added a cowl. I was hoping that would take care of it - just been waiting for a hot day. With the new arrangement, I don't think the engine will overheat, but is running hotter than I would like.

Not sure where to go next. Water pump? Seems like I Need to get more outside air into the engine compartment but don't know how. I don't really want to add a spoiler, prefer not to drive it when it is hot. I don't like that solution either.

the car has 95K miles.

PK

RQB 4143

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Your water pump is probably OK, but I think I'd change to a 165' thermostat. My '85 came with twin electric fans that work alright but definitely do not move air like the full size engine driven fan in My '83. My '83 will run 140-160' in the hot summer if I do not run a 180-195' thermostat. Does your '85 have an engine driven fan with a healthy thermostatic clutch?

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There's a number of things you can do that might help. Start with the basics...check the belts that they're properly adjusted and not slipping. Check the cooling system that it's holding pressure properly...radiator cap included.

How old are the hoses? The lower radiator hose is supposed to have a spring in it to keep it from collapsing under vacuum at highway speeds. If that happens it creates a blockage in the system. Make sure that spring is there.

You can have the engine power flushed...who knows how much buildup there might be in the cooling passages after so many years. Check the fan and fan clutch. If the fan clutch is bad it won't cool properly. Have the engine up to normal temperature and shut it down...the fan should stop rotating almost immediately...after only a couple of rotations. If it continues to spin, the clutch is bad. Electric fans is an option.

What you want is not so much to get more air into the engine compartment...you want to get the already heated air out of it. That's where a spoiler comes into play...it directs more cool air into the radiator and reduces turbulence under the car which helps vent hot air out. I can tell you from experience the Saturn air deflector will help drop temps about ten degrees at speed...it did for my car. Sitting still in traffic it's no help, though. Many Avantis during that time period had holes drilled in the inner front aprons by the factory to help vent hot air out. How successful that was I don't know. Some cars had the holes, some don't.

Make sure the engine is properly tuned. Having the timing off can make an engine run hot.

I wouldn't go crazy changing parts without finding out the root of the issue. Even if you go to an electric fuel pump, that doesn't address the running hot issue. I'd start with checking the cooling system that it holds pressure and flush the entire system and get the block clean and all fresh coolant added. Work from there.

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Well, here is where I am kind of baffled.

Last summer was my first with this car. Runs great, stays cool up to about 90 degrees. Though I was pretty sure the radiator needed replacing, did the power flush and fluid change to see if that helped. It did but still overheated. This spring we put in the new radiator, electric fan and shroud, changed fluids again. The car is driven exclusively in the city (actually small town) and under about 5 miles per trip. On a hot day, it really doesn't get much of a chance to cool itself in such a short distance. The fuel pump theory is when the car decides to die on that damned hill, it acts like it has run out of gas. My mech asks. "how much gas did you have", I said less than a quarter tank. So, he says, fill up your tank and try it again. It may be your gas tank isn't properly "baffled" which of course has nothing to do with the fuel pump. My mech has saved me as much as you guys.

We will try filling the tank. Got a hot day coming on Wednesday.

Grasping at straws.

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Filling the tank to at least half full isn't a bad idea....the fuel gauge itself could be a bit 'off'. Next time you're under the car inspect the entire fuel line including the flex hoses for seeping fuel indicating a pinhole leak...these can drive you crazy, even if you don't see a puddle of gas on your garage floor.

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I'm a mechanic and I see a lot of Avanti owner jump to replacing radiators etc, without starting at the basics.

1- I looked up 1985 Chevrolet 305ci and it uses a 195 thermostat and was designed to operate at this temperature. Running a lower temperature may cause drivability problems. Is the engine overheating or just running hotter then you think it should? If the gauge is OFF by 10 percent that would add 20 degrees.

2- I can cause a older engine to run hotter up a hill by setting the distributer advance wrong. I would be surprised if it was vapor lock as I've never run into it in 35 years as a mechanic. When the engine dies look down the carburetor and operate the linkage and see if it's squiring fuel, if it is that's not the problem. 1980's electronics weren't the best and you may be loosing spark because of heat breakdown of the ignition module or pickup.

3- Start with the basics in your cooling system, this will cause 80 percent of your problems. V belts don't like running at the hotter temps, that why manufactures starting using serpentine belts. Make sure v belts are adjusted correct. Run 50/50 mix coolant, not water. Is your shroud missing or cracked? Is your fan clutch working? Radiator cap the correct pressure and working? Overflow tank working and radiator completely full? Condenser and radiator clean so that air can flow?

I changed my 87 Avanti over to Tuned Port Injection, serpentine belt system and electric fan. Not because it needed it but because I like that type of setup. That setup runs a195 thermostat and the GM factory computer won't turn on the fan until 225 degrees, that is normal.

If you came into my shop I would start by looking at your ignition system first. If you have the large cap GM distributor the advance weights were bad about wearing out and sticking in full advance. After that I would look at your cooling system basics.

Good luck,

Jim

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Thanks Jim,

The Avanti is in the shop right now, I ran your suggestions over to the mechanic. We have a couple of hot days coming up, good time to test your theories.

PK

RQB 4143

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