My '96 subaru started overheating recently. The temp is fine while driving, but the gauge goes up when I stop the car at light, ect. I replaced the thermostat and it ran fine (temp was normal) for five days. Then it started to over heat again just like before. Any ideas?

90

Asked by May 20, 2015 at 12:29 PM about the 1996 Subaru Legacy 4 Dr Outback AWD Wagon

Question type: Maintenance & Repair

My '96 subaru started overheating recently. The temp is fine while driving, but the gauge goes up when I stop the car at light, ect. I replaced the thermostat and it ran fine (temp was normal) for five days. Then it started to over heat again just like before. Any ideas?

13 Answers

40

cooling fan(s)

1 out of 1 people think this is helpful.
90

Fans are working fine.

1 out of 1 people think this is helpful.
90

There is no coolant in oil, or oil in coolant. There is some of the product I used a long time ago to seal the headgasket in the radiator. Could this be the problem? Also, after I stopped and turned my car off. I opened the coolant reserve tank, and air bubbles were going into it through the hose from the radiator. Could this be an air bubble/blockage in the radiator? if so, how do you fix that?

1 out of 1 people think this is helpful.
40

I am working on a similar problem right now with my 91 legacy. I am possibly looking at compression from a head gasket leak. Is your radiator drill blocked at all? leaves etc..do your rad hoses become hard and prssurized? My car does not overheat will idling like yours. only when driving I will probably have to do the head gaskets and flush rad in my project

2 out of 2 people think this is helpful.
90

Any idea how to tell if it is the head gasket? I am told if: the heat works, there is no oil in radiator, and no antifreeze in oil, THAT IT IS NOT THE HEAD GASKET. ??? The rad hoses are hard & pressurized. I don't know what the rad drill is? Not sure if I miss spoke, but MY CAR ONLY OVERHEATS WHEN IT IS IDLING, BUT ONLY AFTER DRIVEN. WHEN DRIVING THE TEMP IS FINE, BUT I ASSUME BECAUSE AIR IS COMING INTO THE FRONT OF THE CAR. The water pump was changed not long ago. The fans work. I am thinking of flushing the rad. Any ti

5 out of 5 people think this is helpful.
1,020

I have 2 Subaru Legacy's. Both have given me the same problem at various times. The solution is ridiculously simple. Air gets trapped in the heater element, which sits under the dashboard and is higher than the radiator so that the air does not bleed out. There is no independent thermostat bypass in a Subaru. The hot water flowing through the heater element re-joins the main cooling system at the thermostat and acts as the thermostat bypass, heating up the thermostat so that it can open. The thermostat is at the bottom of the engine and receives cool water coming back from the radiator which causes it to close unless the bypass coming via the heater is flowing properly to keep the thermostat hot. So if you have an airlock in the heater element your car will overheat because the thermostat is not getting hot water to open it. This tends to occur more at low revs, like when driving in traffic. If you rev the engine this often pushes more coolant through the heater and opens the thermostat and suddenly the engine cools down again. The way to prove this is to bypass the heater element. Get or make a u-bend of 16mm metal pipe and disconnect the two heater hoses at the firewall behind the engine and join them together with the u-bend and two hose clamps. The overheating problem will go away for good. But of course, now you have no heater. The best solution if you want your heater to work is to cut both the heater hoses at a suitable spot next to each other and to fit a T-piece in each hose and join them together. (See photos). Then water can bypass the heater element keeping the thermostat functioning properly, and enough hot water will still flow through the heater element to warm up the car's interior. This is the best solution, because every time you have work done on the cooling system, air gets in and it is almost impossible to get it out of the heater element again. You then get erratic overheating problems when you least expect them, and the symptoms mimic a blown head gasket, with water being blown out of the radiator and the expansion tank overflowing. Alternatively one can try to clear the airlock from the heater element by disconnecting the left heater hose and back flushing the element with a garden hose, then quickly reattaching the hose while trying not to let air in. But the above solution with the two T-pieces to bypass the heater element has worked better for me and provides a permanent solution, and getting air out of the cooling system after any future repairs will not be a problem again. In the photos, I used a straight piece of hose to join across the T-pieces in the one car, and I used a U-shaped piece of hose in the other car. The U shape allows one to get away with not getting the T-pieces perfectly aligned, but can be hard to obtain. However a spare of the rubber bypass hose that attaches the metal bypass hose to the thermostat housing is the right shape and diameter.

43 out of 43 people think this is helpful.
1,020

I used a straight piece of hose to join across the T-pieces in the one car...this is that photo: -

10 out of 10 people think this is helpful.
435

Go to technician that has an air lift tool , drain completely , draw sus into complete vacuum 27 inches , then attach refill device that come with air lift tool and refill system with coolant to 70 / 30 mix of low celicate coolant

1 out of 1 people think this is helpful.
435

No air no overheat , as long as lower radiator is not blocked,it would also be a good time to use headgasket / block test when suspect air bubbles are coming to recovery tank or radiator cap opening depending on vehicle design. Hopes speeds your repair process

1 out of 1 people think this is helpful.

Hello Anthony_60. Quick question. I'm experience a similar situation with my 2002 Subaru Outback I even removed the Thermostat which will allow cool water thru the engine to avoid the overheat issue but still experience the same problem.

1,020

Hello Jorge, I am sorry but I don't have an answer to that. If the thermostat is out then the water should flow freely whether there is an airlock in the heater element or not. Maybe the radiator is clogged up? Or if you have replaced an original aluminium core radiator with a made-up copper one then it will be much less efficient unless it has a double core.

1 out of 1 people think this is helpful.

Hello Anthony_60, Thanks for your quick response. Do you know where I can get the house and connectors to do the bypass?. Thanks

1,020

I bought mine at a shop specializing in hydraulic and other hoses. But I am in South Africa... probably not where you are...

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