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Old 12-27-2019, 09:55 PM   #1
1bigdoggie
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Default OVERHEATING - blowing out coolant

Ever since I had the engine worked on for a complete valve job (new head, etc..) I have had an overheating issue. Have traced it down to COOLANT LOSS at such a rate that eventually the engine will overheat. The coolant is being blown into the overflow tank, and from there, after it fills up, it blows out the top and continues to do so until there is not enough coolant left in the system (down about 50 ounces or more) and then the engine overheats and pings the needle red.

Anyone know how this can happen? Why is there so much pressure build up to blow out all the coolant into the overflow and beyond??

ANY HELP is appreciated.
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Old 01-02-2020, 05:34 PM   #2
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Does the coolant overflow the tank while the car is running or when you shut it down? The blown head gasket syndrome rears its ugly head typically after you shut the engine down. Other things to check would be the thermostat by taking it out and boiling it in water to see if it opens. Make sure when it's installed that the spring portion is going into the block housing and not the other way around. Did you have problems before the rebuild? Make sure your radiator is not rotted or clogged internally or externally. Check for leaves and debris between the radiator front and the air conditioner condenser rear blocking airflow. Take the radiator And look inside to me if cores are blocked by corrosion. One way to check for flow is to put a garden hose going into the top and see that it flows freely. Rinse with distilled water. You might want to check under the oil filler cap to see if there's any gray sludge from coolant getting into the oiling system. Head bolts should be torqued to 72 foot pounds for standard bolts or 90 for ARP studs with nuts and the ARP grease. Fan clutch working normally? If have a blown head gasket you need to talk to whoever worked on your engine. Using a stacked metal head gasket requires precision surface treatment. Are you blowing oil out of any of the seals? That would indicate compression a leak into the Oil system.

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Old 01-04-2020, 12:44 AM   #3
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Bru. Thanks for the reply. Coolant is being blown out into the overflow, and then completely out of the overflow tank WHILE BEING DRIVEN.

Everything had been changed on the car. Thermostat. Fuel injectors, Radiator cap. Radiator, Fan Clutch. Water pump. You name it.

Originally had an oil leak from valve seals. Had that work done and when car was given back to me, I overheated and blew the HG on the first day. They replaced he HG, and it overheated again !! So they said instead of doing this again, to replaced the engine. Had the engine replaced, and then overheated the very next day. Replaced EVERYTHING as stated above. When nothing helped, I realized the car only overheated when it lost 50+ ounces of coolant, and could no longer cool the engine. The coolant loss is due to it being blown out of the overflow tank.

I now suspect the HG again, but it passes the Hydrocarbon tests, usually indicating an intact HG.
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Old 01-04-2020, 02:48 AM   #4
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Very strange that this condition would happen to 2 different engines if I read your reply correctly. I was going to suggest that the head or the block was warped. Seems combustion gases are leaking into the cooling jacket. I've seen blocks and heads that were unusable because the cooling passages, especially on the combustion side, were rotted too close to the sealing ring around the cylinders. What type of head gasket are you using? Standard Toyota or aftermarket stacked metal? When I had my block and head shaved they took off 20 thousandths more than Toyota allows which is 10 thousandths total. I used a 0.020" METAL shim gasket on top of the block sprayed with Permatex Copper on the bottom only. Then I used a standard Toyota head gasket on top of that. I've had no trouble after 35,000 miles. One of the hardest things to find nowadays is a head that hasn't been cooked soft or over cut. Several of the exhaust manifold studs on mine had to be replaced using helicoils to renew the threads.

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Old 01-04-2020, 04:24 AM   #5
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Yes, very strange indeed. This is why we can't figure it out. The only thing in common between the two test drives after I got the car back, was the fact that the heater core was not bled (coolant filled) properly, due to a non-functioning heater core valve. The only thing I can think of is that too much air was then in the cooling system both times, causing it to overheat on both engines, and causing the HG to blow both times. Of course, this is ONLY A GUESS.

Anyway, I have no clue what kind of HG was used on my original engine when it blew twice, and I have no clue what is in the replacement engine, because it came intact (full engine: block plus head)

After talking to another guy on this thread, we will do a leak down test to see if HG is intact or not. That is the only thing I can think of that would inject enough air into the system to cause a gurgling sound under the dash and to blow out coolant into the overflow, and out of that until it looses 50+ ounces and overheats. Have my fingers crossed. If you can think of anything else that can cause so much fluid to be blown out (by what we think is high pressure in the system during heavy load), please let me know.

Thanks for your time and thoughts.
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Old 01-04-2020, 04:49 PM   #6
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A leak down test is definitely a good diagnostic approach. Keeping the piston at top dead center during the test is a chore. Another thing I forgot to mention is that when the block is shaved at the machine shop, the front cover that bolts onto it also needs to be there during that procedure in order to make them a level because the head rests on both of them. I made this mistake myself. There could be a step down between the front cover and the block which doesn't allow the head gasket to seat properly. It's easy to check by looking behind the alternator under the right valve cover to block vent hose.
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Old 01-04-2020, 07:02 PM   #7
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Thanks for the tip about machining the block. I don't think it will come to that, as I am about to give up and scrap the car if changing the HG doesn't work . (Assuming it fails the leak down test and my mechanic agrees to re-do the HG gasket) But, if any machining of the block takes place, I will remember this.
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Old 01-05-2020, 05:10 PM   #8
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Are you seeing a cloud of white smoke on start up or while running? Burning coolant it looks like that. Burning oil looks more gray. A crack in the head can allow compression / combustion gases into the water jacket. It's $50 well spent to have it checked at a machine shop that can perform a magnaflux type dye test even though the head is aluminum. The head should be completely disassembled including valves removed. There are also do it yourself preparations on the market. Here is a YouTube page with various methods. https://www.youtube.com/results?sear...lux+head+test+
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Old 01-05-2020, 07:54 PM   #9
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No white smoke at start up. Seeing blue and gray smoke. I believe that is oil. The original reason I took in the car. Had valve seal leak. So had a new head put on. Solved the oil leak smoking problem at start up, but over heated the very next day. Blown HG. Replaced. Over heated the very next day. Could over heating have cracked the block? The question is WHY did it overheat in the first place, after a head replacement. All was good with the car for 30 years besides the oil leak in the valve seals. Anyway, shop talked me into a replacement engine. Very first day it over heated as well. And I've been here ever since. How can it be that TWO blocks are cracked ? I don't think that is the issue. Oh, and the replacement engine now blows smoke (oil leak) upon start up, which is why I had the head replaced in the first place.

Anyway, will do the leak down test to check the integrity of the HG. I'm really hoping it is that. Because if not, we are basically out of ideas. Will not be able to tear the car apart and get the block checked for cracks. But MAY be able to check the OLD block for cracks. If no cracks in it, then the overheating is caused by something else.
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Old 01-06-2020, 04:05 AM   #10
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Here are pictures of a block that has rot around the cooling passage right up to the fire ring where the gasket seals and a picture of a block in good shape. It's easy to see the difference. As far as cracking goes, the head is more at risk than the block because aluminum is a softer metal than iron.
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