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My ongoing temp/oil pressure problem.........

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Can Can, May 15, 2001.

  1. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    As a few of you know, the other day the Blazer started running warm with low oil pressure. I was worried that my oil pump was dying, causing my engine to run warm. We ended up agreeing that the problem was probably somewhere in the cooling system, so today I drained my rad and replaced my thermostat and coolant.

    I'm glad to report that my oil pressure seems to be back to normal. 40PSI cold, 25-30 warm. However, I'm still getting some funny temp readings- The truck starts up, gauge reads cold, then it seems to take longer than normal for the thermostat to open as my coolant get hot(This could simply be a result of having a new thermostat). Once I start driving, it gets wierd!!!!!!!!!! When I accelerate hard, it starts to heat up. If I keep driving, it seems to stay a little warm, but when I stop and idle for a few seconds, it starts to cool off!!!!!!!?????? This is totally the opposite of any cooling problem I've had in other vehicles. Normally, idling will bring on the heat and driving will help to keep things cooler...............This truck has NEVER had an overheating problem, ever.

    Any suggestions would be appreciated. FYI, I have a newer rad, a newer water pump, and this problem just started out of the blue on Saturday.

    Help me..............my hair is too short to pull out!!!!!!!!!!!!!!!!!!!!!!!!!!!



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  2. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    Did you try the temperature sending unit? Do you think it is getting hot and you are getting true represenation from the gauge?
    (probably tired of hearing from me....)
     
  3. Wheels

    Wheels 1/2 ton status

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    Check for a hose (suction side) that is colapsing. Had this happen on a 86 IROC ten miles outside of Fayetteville Ark. Doing the same thing you are describing. As you rev'd the engine, you could see the lower hose colapse. Limped back to town and I was lucky that the only parts store had the hose.
    Also, had a 68 Bronco that the inside of the lower hose started to seperate from the rest, my little sister burnt that motor up for me while I was overseas.

    <P ID="edit"><FONT SIZE=-1>Edited by Wheels on 05/15/01 06:33 PM (server time).</FONT></P>
     
  4. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Never tired of feedback, 96C4[​IMG]!!!!!! My next step is to replace the sending unit.......but for all I know it could be a gauge problem. Where is the coolant sending unit on my 305? I can't tell if the motor is running too hot- all I've been going by is the gauge!!!

    Wheels- After we put the kids to bed, I'll get my wife to help me check out your hose suggestion. I don't think that's the problem(I did the rad hoses when I did the rad last summer), but it's definitely worth a try.

    Is there a chance it has something to do with my fan/fan clutch? The engine hasn't gotten warm enough to engage the clutch........In fact, it's not even close to overheating, but something has to be wrong somewhere.........

    Man, this is KILLING me!!!!!!!!




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  5. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Somebody? Anybody? I don't know what steps to take to solve this problem..................



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  6. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    I think the sending unit is under the exhaust manifold behind the PS pump.
    I can't think of anything else at the moment - will sleep on it.
     
  7. Wheels

    Wheels 1/2 ton status

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    If you've already replaced the hoses, next would be the fan/clutch or maybe the vanes on the water pump are cavitating at higher engine speeds. Hard to tell without tearing it apart.
     
  8. Itali83

    Itali83 1/2 ton status

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    Hey my truck is doing the same thing!! Warm at driving but cooler at idle. But my motor had other probs before this. When I first got it the intake manifold gaskets were put on backwards, causing it to overheat with a thermostat in it. but once I got that prob taken care of... After, brand new water pump. hoses, new radiator. Now the guage (with new sending unit) will read 210 cruising and at a long light, it will go down, I'm guessing to the 185 area on the guage. I have a solid flex fan on there for the moment but going to get factory clutch fan. The shop said that my guage was wrong and just reading a little too high and my truck was only running at 195 instead of 210 like my guage says. I can but that because the factory guages are JUNK!!! But anyways. I have the same prob you have when driving and then stopping. Weird stuff. My hoses are new along with the pump, so I can't see how there would be a suction problem at high rpm's.
    Your temp sending unit is on the right bank of the motor between the front two exhaust ports. Cant miss it, It should have only one wire coming out of it. So if you find out why the temp thing is crazy. write back or send me a personal, because I would like to figure this one out also.
    Ben 87 Jimmy
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  9. muddin4fun

    muddin4fun 3/4 ton status

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    It's on the driver's side of the block on the heads I believe somewhere around the exhause manifold. So it'd be on the side of the block towards the front. It'll have a little wire running out of it.

    [​IMG]
    <A target="_blank" HREF=http://k5chevyblazer.homestead.com/home.html>http://k5chevyblazer.homestead.com/home.html</A>
     
  10. CaptCrunch

    CaptCrunch 1/2 ton status

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    Just my $.02 here, but why don't you find out the temp of the coolant first before throwin money into the sensor and guage. Another thing to consider is if you have air pockets in the cooling system after the thermostat? Was this like this before the stat was replaced or was it just overheating? The guage bouncing up and down or doing what you describe is a classic symptom of air pockets... also can check to see if you have heat when it warm up (heat like inside the truck I mean) Easiest way to get any trapped air out is to get a flushing Tee at the parts store or even a local garage... you could also have them hit the engine w/ a laser temperature reader to see if indeed it is as warm as the guage says. Next would probably be a water pump problem or problem with coolant circulation.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  11. jarheadk5

    jarheadk5 1/2 ton status

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    I'm starting to think it's a combination of what Wheels and CaptainCrunch said. My first thought was waterpump cavitation, after the comment about hot at cruise and hard driving, but cooling off while idling. Then CaptC got me thinking about trapped air, and I realized trapped air can cause cavitation, or make a small cavitation problem much worse.
    There's my 2 cents...

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  12. Itali83

    Itali83 1/2 ton status

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    If air is getting somewhere. Where, how does it get there, how do I get rid of it? Heater works fine, never gain/loose antifreeze (I check it all once a week with my oil checking). Just wondering, I've heard that the small blocks are known for air pockets, so I just want to know more about them. Thanks
    Ben 87 Jimmy
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  13. jarheadk5

    jarheadk5 1/2 ton status

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    Heating water causes "air" to come out of suspension in the liquid. Technically, the different gases that make up our atmosphere (nitrogen, oxygen, etc) will leave suspension at different temps, and if the cooling system is well-sealed, then the gases will end up trapped in sharp corners of cooling passages, in the heads, and other little annoying places. The quantity of gases that will leave suspension in a cooling system can cause problems, especially if you use tap water, which is chlorinated and aerated so there's lots of gases suspended in it.
    Use distilled water for mixing coolant, and you'll eliminate one of the causes of trapped air.

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  14. JoeAngelicchio

    JoeAngelicchio 1/2 ton status

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    Paul, could your belt be slipping when it gets a bit of a load as in accelerating or higher rpms? If the belt slips the water pump won't be working properly.

    <font color=green>Joe Angelicchio
    86 Jimmy 4+3, 35-&gt;39.5 tires,4spd
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