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coolant purging sounds like a knock

1stimer

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91 ford explorer
so i have a 91 explorer that recently got new water pump, radiator and lower intake gaskets. now i have a knocking noise at idle after the motor warms up. the noise is mainly at idle or a slow cruising speed. i can feel the coolant purging in the upper radiator hose. also when i raise the idle with the hood open it sucks the upper radiator hose flat. what might be goin on?? :(
 



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1stimer

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91 ford explorer
i have read thru alot of the threads here and it seems most people with this problem have a guage that fuxuates too i do not have this problem even though it sounds like someone is kicking my passanger firewall i can feel it most up by my thermostat which was also replaced
 






mr cribb

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Sounds like you have air in the system. Have you bled the air out of the radiator after water pump install?

How is the heat in your truck? good, or none? If none I recommend the heater core($25, 10 min job), but you don't have a jumpy temp gauge.

Key thing to watch is the temp gauge. One thing I learned just a few weeks ago while chasing an overheating problem.... the temp gauge shouldn't go beyond "R" (middle of gauge) that is roughly 200 degrees. Mine was going to the "A" and not coming back down. That is 220.

I installed a real number temp gauge to figure all this out.

My problem was a cracked head. With rad cap off and engine running I had small bubbles (pretty constant) then is upgraded to a gushing out of the radiator. Using my mechanic background, I traced it to cracked head. (Symptoms include: excessive overheating, loss of coolant, steam out the tail pipe on a 65 degree day, gushing of coolant from radiator). Even the guy at Clearwater Cylinder Heads confirmed my suspicions. So if you run into this problem, the heads will run you $480, and a good gasket kit is about $150, don't forget head bolts.

Hopefully you never have to deal with this issue but if you do, there's the prices, description of problem. Good luck.
 






1stimer

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thanks

that's what I thought but ive tried everything to bleed it out I even stuck it nose up on the steepest hill I could find but I still have the problem :( my temp guage acts normal heats up then has the first drop when thermo opens the sits a little under half way up still havnt lost coolant but I am loosing my mind! :roll:
 






malohnes

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'91 xl m5 4x4
Make sure your coolant recover tank has fluid in it when you purge the the lines.

I did this to my truck:
Park up an incline, insert a funnel in radiator to allow some fluid to rise out and not leak on the ground, let the engine warm up, squeezing the top hose with a glove on and allow bubbles to come out, gently rev engine a bit, a coolant as needed, level with the bottom of radiator neck, shut off engine and cap off radiator and allow to cool. Do this 2 or 3 times and that should get the bulk of your air out.

I found in my rig that the recovery tank, if left low or empty can allow air to get back in the system after coolant change, or engine work where coolant is drained and refilled and the problem seems to reappear.
 






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