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Steve near Chicago
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Overheat
Oct 8th, 2019 at 5:09pm
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My ‘86 N/A overheated on the way home, blowing off the lower radiator hose at the water pump housing. Pulled and tested the thermostat which tested OK. Water pump?

Thanks in advance,
Steve near Chicago
  
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OhioTom
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Re: Overheat
Reply #1 - Oct 8th, 2019 at 8:35pm
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Hmm. Usually that means thermostat.

But..
Has she been using coolant?
could it have been low on coolant?

I know when they get low, they can get an air pocket in the system that remains in the head. This will lead to overheating and over-pressurization of the system.

Usually, over-pressure vents out the cap on the reservoir.
The fact that it blew a hose off and didn't blow off the overflow reservoir cap makes me think the hose/clamp was bad anyways.
The stock German clamps give up after a while. I just replace all the clamps when doing the waterpump anyways.
Re-using old clamps always leads to a leak.

  

Tom Simpson&&VW/Porsche freak.
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Steve near Chicago
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Re: Overheat
Reply #2 - Oct 12th, 2019 at 4:28pm
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It had been using some coolant but I don't believe it was low. Starting to think maybe head gasket. How would I check that?

Steve
  
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OhioTom
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Re: Overheat
Reply #3 - Oct 14th, 2019 at 3:34pm
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I had a head gasket failure that would push compression into the coolant. Accumulate gasses in the head and then overheat.
I was constantly burping air out of the system, and still having overheating issues.

The way I found it was:
Park the motor at TDC #1. Now pressurize the cyl with compressed air. (part of my leak-down tester kit). Remove the cap on the reservoir.
Wait a few min and look for air bubbles in the coolant reservoir.
Don't see any?
Go to TDC #2 and repeat.
When I finally found the leak, a steady stream of air bubbles was running into the reservoir.

Luckily, it was compression leaking into the coolant. Not the other way around.


  

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Dave W
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Re: Overheat
Reply #4 - Oct 14th, 2019 at 4:57pm
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A lot of overheating problems are due to air in the system.  You do have to burp/bleed it to get things to run smoothly.

But there is a way that air gets in/steam gets out of the system.  An old radiator cap will allow steam out instead of keeping it pressurized.  This loss of steam over a few days causes "low coolant" and air in the system.  Then it looks like you are overheating.

Check the cap.  It's cheap to replace.
  

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Cambo
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Re: Overheat
Reply #5 - Oct 15th, 2019 at 3:40am
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Make sure you buy a good cap with the correct pressure rating as well. Typical radiator caps are 15-16 psi, but if I'm not mistaken I believe the cap for these cars are actually rated higher.

And oh yeah... Sometimes it can be a real treat trying to burp the air out of the cooling system on these cars...
  

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OhioTom
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Re: Overheat
Reply #6 - Oct 15th, 2019 at 2:37pm
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How to bleed the air out:

Locate the bleed screw on top of the coolant return fitting. Crack it loose but leave it just snug. Leave the wrench on the plug so you can easliy open/close it.
Now grab the upper radiator hose with your hand.

Just like bleeding brakes, do this: Remove reservoir cap;
Crack bleeder; squeeze hose and hold; close bleeder; let go of hose; repeat....
If you are making progress, you will see the coolant level drop in the reservoir after each "pump" of the system.

The idea is to open the bleeder, squeeze the air out, then close the bleeder.
Eventually, you will get nothing but a steady stream of coolant pushing out when you squeeze. This means you are done. Set the bleeder tight and put cap back on reservoir.

  

Tom Simpson&&VW/Porsche freak.
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Steve near Chicago
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Re: Overheat
Reply #7 - Oct 15th, 2019 at 10:00pm
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Not sure it was low coolant. I don't remember the fans running and now it won't start. See my other thread.

Thanks for the help,
Steve
  
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