1997 subaru legacy PDTS (post deer traumatic syndrome)

So after hitting a deer in my car a few weeks ago I fixed it and drove it around town a little bit and it ran fine. But 15 mins onto the highway the next day it overheated. It was out of oil, which I had checked a couple days before when I fixed it. so after it had cooled down I filled it up with Coolant and oil and started driving it home. the roads where bad and I wanted to go easy on the engine so I took it at about 25-30 MPH. as I was driving it would slowly overheat, but I could get it to start cooling down but dropping it into neutral and just letting it idle while I coasted. I had to get off the frontage road and take the highway the last couple miles before town so I turned the engine off and let the fan run for about 20 mins, and started off again, the weird thing was when I got on the highway I was doing about 55Mph and the engine didn’t try to overheat at all, but as soon as I got back in town and started doing 25 again it started overheating again. another thing that is happening is that the car will blow air through the heating system but won’t heat it. I realize that was long but I’m really at a loss. I replaced the head gaskets less than a year ago so it’s not from worn gaskets. But I can’t figure out what the problem(s) is/are. Any advice would be appreciated.

If the engine is blowing bubbles through the cooling system, your headgasket(s) is/are breeched.
You can easily confirm this by doing a chemical test on the coolant for evidence of hydrocarbons. Kits are inexpensive and readily available.

If you hit a deer, it usually means you have to repair the cooling system.

One thing to check is to make sure that there’s no air trapped in the cooling system. If there is, it can cause aeration of the coolant causing bubbles which can cause the coolant to stall at the water pump.

To make sure all the air is removed from the cooling system, start the engine and let idle until the cooling fan comes on.

Loosen the upper radiator hose clamp, and with a small flat bladed screwdriver insert it in between the upper radiator hose and the hose neck on the radiator. Allow the engine to continue to idle until all the air is removed from the cooling system.

Remove the screwdriver and tighten the hose clamp.


The radiator isn’t blowing bubbles. But the engine hasn’t lost anymore oil. So I filled the radiator up and found a hole in it, so I added some block seal that is supposed to seal small holes in your cooling system , and started the engine. After a few minutes of running, it stopped leaking. So after that I waited for the engine to get up to temp and opened the air bleeder on the top of the radiator and started pouring coolant into the radiator. After a little while the bleeder started blowing steam but the engine wasn’t over heating, and we so closed the radiator up. Then we took off the hose from the heater core and it wasn’t getting any flow, but the hose to it was hot. Plus we’re still not getting any heat from the vents. But as soon as you raise the Rpms the temp gauge spikes immediately and when the engine idles the temp gauge slowly lowers. So I’m still baffled.

I think you have some combo of air remaining in the cooling system and/or the radiator fans aren’t coming on in slower speed driving and idle like they should. Take the car back and ask your shop to address those items. Make sure they check the radiator cap too.

If you have any small leak at all in the cooling system it will usually overheat. That’s not b/c of loss of coolant, but b/c it isn’t holding pressure. You have to completely make the cooling system air tight and holding pressure first, before stating to speculate what else might or might not be wrong. Shops have simple tests to determine if the cooling system holds pressure or not.

It’s sort of hard to understand how come the cooling system gets hot enough to overheat but no heat from the heater. But if you think about trying to hold an air filled ball underneath the water when you go swimming, think how much force is required, then it should be more easy to understand. The heater core is low to the floor, so the water pump has to push fluid down to it, but if there’s any air in the cooling system the water pump doesn’t have enough ummpth to overcome that air filled ball in the swimming pool effect.

It is possible when you discovered you were driving the car without engine oil, that could have caused damage to the engine. Unlikely though unless it involved extended or higher speed driving or the crankcase was in fact completely empty. Most times when posters say there was “no oil” they mean none showed up on the dipstick test. But there’s usually some still in the crankcase. That’s usually enough for short trips as long as the engine oil warning light on the dash isn’t coming on.