Overheating (again !!!) Legacy 2.0 GT 1990

[New Subaru Fan]

My old 1990 Subaru (190 000km) starts overheating after 15 min of driving.

 

The engine was rebuilt about 4 weeks ago. We replaced head gaskets, timing belt incl. the tensioner, water pump, thermostat and radiator. After the rebuild of the engine the car ran greatly, no overheating even under severe driving conditions. No leakage of coolant could be observed. But a couple of days ago the engine overheated quickly just during normal driving. In the beginning I assumed the overheating was because of the air pockets, I bled the cooling system a couple of times but the overheating problem was still there. The pressure in the cooling system seemed to be very high as I noticed yesterday that the upper radiator hose was leaking. I tightened the clamp today an that leakage stopped, but the car was still overheating.

I live on the hill, so I needed to get back home. The engine overheating gauge was showing 90% as arrived. I checked the engine after arrival. No vapor was coming out, and there was coolant coming out of the overflow system (the radiator cap is alright). But I also found there was something else leaking, it was in the area of water pump. That area was not leaking yesterday. I don't think that was the cause of the problem, as it was not leaking as the overheating started a couple of days ago and I assume that this leakage occurred due to the very high pressure in the cooling system.

The interesting thing is I can't here the water flow through the system inside when I turn on the engine (I used to hear that sound before). The heater in the cabin is working, however it only starts to heat after about 5 min of driving.

 

I have no clue what it could be. Can anybody help me with this? I'm desperate. It took us huge effort to replace the head gaskets etc, and now a similar problem arises.

 

[Platinum_Racing]

It could be a bad water pump that was installed. It could also be water pump gaskets. I think the radiator hose is a coincidence, but its a good idea to bleed the system again after you replace the hose.

 

It could be head gaskets, but I would look into the water pump first, as a major leak like what you're describing is probably letting air into the system.

[New Subaru Fan]

It could be a bad water pump that was installed. It could also be water pump gaskets. I think the radiator hose is a coincidence, but its a good idea to bleed the system again after you replace the hose.

 

It could be head gaskets, but I would look into the water pump first, as a major leak like what you're describing is probably letting air into the system.

 

Thanks for the comment.

Do you think of other possibilities? For example thermostat?

The lower radiator hose is intact. The clamp was too loose, so I tightened it enough and it's fine now.

I was also thinking about the head gaskets. But we polished the heads and engine block surfaces quite well. I can't believe those things are leaking again. I also checked for bubbles coming out of the cooling system while idling. But I couldn't see any constant appearing of bubbles.

 

It can be a water pump. But that area close to water pump started leaking today. I didn't see it leaking on the first and second days of overheating, but I'm not quite sure about that.

 

The water pump was brand new as we installed it 4 weeks ago.

[New Subaru Fan]

I'M GOING MAD!

 

Here's what I've done today:

1) tightened the hose that was leaking

2) proved the water pump was definitely not leaking

3) took out the thermostat and tested it using an old but functioning one as a reference (hot water test in a pan)

3) checked there was no external leakage of coolant out of the system

4) bled the system to get rid of the air

5) drove the car for about 5 min - she overheated

 

6) had a rest and a beer ...

 

7) took out the thermostat

8) bled the system

9) she overheated again!

 

My observations:

- the coolant level was constant (by the way it was not the case as I had my head gaskets blown)

- the heater was not working well (I clearly noticed that as I was cooling down the engine on my way back home: the heater didn't blow warm air despite the engine was on)

- the engine temp. gauge didn't tend to fall down when I stopped to cool down the engine (the engine was on)

- and the most interesting thing: I couldn't hear that sound of flowing coolant each time I turned the engine on (but I used to hear that sound before)

 

So the question is:why cannot this sound of flowing coolant while turning on the engine be heard anymore?

Does this overheating problem have anything to do with the absence of coolant circulation or is it somehow related to the heating system?

 

I'm even starting to think that the water pump isn't working at all. Or there is s a physical obstacle somewhere in the cooling system causing therefore absence of circulation.

 

DO YOU GUYS HAVE ANY IDEA ???

 

I really want to keep this car! I actually quite love it.

[SBT]

Have you always used Subaru coolant and conditioner in the cooling system. If not, then my first suspicion, if it's not HGs, is that the radiator is plugged with crud (read chemical buildup) in the radiator and the block from using coolant that isn't made for the Subaru alloy block. It will also cause your water pump to crud-up and start leaking. Did you follow the Subaru bleeding procedures for the block, when you re-bled the system, to make sure that you don't have air bubbles in the system. That will give you an immediate hot-spot and likely cause HG failure.

 

1st do a leak-down on the engine. If that's good, then I'd flow check the radiator. If that's good (and my sense is it isn't), then I'd move on to the rest. I mention the radiator because it sounds like it's blocked and the hose is just relieving the pressure that can't get through, which would also explain that your water pump is now leaking...

 

Just a couple of quick thoughts.

[Platinum_Racing]

I was going to tell you to make sure the thermostat wasn't backwards, but since the car still overheats after you remove the thermostat entirely this doesn't apply.

 

If there is enough pressure to make the coolant squirt out of a tiny leak like the lower radiator hose, chances are the pump is doing it's job. It could be possible that gunk has found its way to the radiator where it has become lodged. I'd remove the radiator (Really easy, as you probably already know) and flush it out with a garden hose. Fill the radiator with water with no hoses attached and see if it flows out the other side. Make sure to cover up the transmission part of the radiator. You don't want any moisture to make it's way into the transmission fluid when you put the car back together. If you tuck the transmission hoses somewhere in a high enough spot when you remove them you shouldn't lose more than a quart of transmission fluid (The contents of the transmission cooler).

 

It could also be a blockage of the heater core. These are extremely expensive, so it's worth it to remove the blockage before trying to buy a new one (Since Autozone lists the part for about $370 new). Its a pain in the ass though, since you will have to remove most of the interior to get at it. Here is a diagram.....

 

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/06/70/87/large/0900c15280067087.gif

 

That just shows you how to get the heater core out, you still have to take the entire dashboard apart to get at it.

 

Consider this a last resort. Unfortunately, it looks like you're getting closer and closer to that last resort.

[Platinum_Racing]

GAH!!!!!!!!!!

 

Subietronic you beat me to it!!!!!! It took me so long to compose that post that you swooped down and stole my idea!

[New Subaru Fan]

Have you always used Subaru coolant and conditioner in the cooling system. If not, then my first suspicion, if it's not HGs, is that the radiator is plugged with crud (read chemical buildup) in the radiator and the block from using coolant that isn't made for the Subaru alloy block. It will also cause your water pump to crud-up and start leaking. Did you follow the Subaru bleeding procedures for the block, when you re-bled the system, to make sure that you don't have air bubbles in the system. That will give you an immediate hot-spot and likely cause HG failure.

 

1st do a leak-down on the engine. If that's good, then I'd flow check the radiator. If that's good (and my sense is it isn't), then I'd move on to the rest. I mention the radiator because it sounds like it's blocked and the hose is just relieving the pressure that can't get through, which would also explain that your water pump is now leaking...

 

Just a couple of quick thoughts.

 

Thanks a lot for your thoughts.

No, I didn't use the original Subaru coolant, but I haven't been using it before I replaced the HGs neither.

 

I took out the radiator today and it seemed fine (I simply blew air through it and I couldn't feel any obstacles). Also this radiator was replaced about a month ago.

 

The water pump is not leaking, there was a hose leaking above the pump, but I tightened the clamp of that hose and it was fine in the end.

 

I might do the leak-down on the cylinders. But hopefully there's something minor than HGs (I'm very reluctant to have to replace the HGs again).

 

Could you please tell me what the Subaru bleeding procedure is?

Thanks.

[New Subaru Fan]

I was going to tell you to make sure the thermostat wasn't backwards, but since the car still overheats after you remove the thermostat entirely this doesn't apply.

 

If there is enough pressure to make the coolant squirt out of a tiny leak like the lower radiator hose, chances are the pump is doing it's job. It could be possible that gunk has found its way to the radiator where it has become lodged. I'd remove the radiator (Really easy, as you probably already know) and flush it out with a garden hose. Fill the radiator with water with no hoses attached and see if it flows out the other side. Make sure to cover up the transmission part of the radiator. You don't want any moisture to make it's way into the transmission fluid when you put the car back together. If you tuck the transmission hoses somewhere in a high enough spot when you remove them you shouldn't lose more than a quart of transmission fluid (The contents of the transmission cooler).

 

It could also be a blockage of the heater core. These are extremely expensive, so it's worth it to remove the blockage before trying to buy a new one (Since Autozone lists the part for about $370 new). Its a pain in the ass though, since you will have to remove most of the interior to get at it. Here is a diagram.....

 

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/06/70/87/large/0900c15280067087.gif

 

That just shows you how to get the heater core out, you still have to take the entire dashboard apart to get at it.

 

Consider this a last resort. Unfortunately, it looks like you're getting closer and closer to that last resort.

 

Thanks a lot for the idea and the map.

 

What did you mean under transmission fluid? My radiator is really simple and I don't think there's any other sort of fluid apart from the coolant circulating through the engine.

The idea of blocked heater core is pretty realistic. I've already seen some posts on that issue on the internet, However, our Subaru mechanics said they had never heard about that.

I would prefer to get the entire dashboard apart etc. rather than pooling the engine out and putting it apart to replace the HGs again.

 

What are actually typical symptoms of the blocked heater core in older Subaru Legacy?

 

Cheers

[Platinum_Racing]

If you don't have a transmission cooler built into the radiator, then by power of deduction I assume the car is a manual transmission.

 

Most modern automatic transmissions either have a section in the radiator that's separate from the engine coolant designed to maintain the temperature of the automatic transmission fluid, or a separate transmission cooler mounted (Usually) in front of the radiator.

 

Signs of a blocked radiator or heater core are pretty much what you're describing. Too much pressure causing hoses to leak, primarily around the area where they get clamped to something, or leaking gaskets around the water pump, or in some cases the water pump itself.

 

If it's the heater core it's pretty much the same deal as the radiator, only underneath the dashboard instead of in front of the engine. The heater core is just a little radiator with ducting designed to transfer the engines heat to air used to heat the cabin. It uses a similar design as a radiator, so it can be prone to the same issues.

[New Subaru Fan]

If you don't have a transmission cooler built into the radiator, then by power of deduction I assume the car is a manual transmission.

 

Most modern automatic transmissions either have a section in the radiator that's separate from the engine coolant designed to maintain the temperature of the automatic transmission fluid, or a separate transmission cooler mounted (Usually) in front of the radiator.

 

Signs of a blocked radiator or heater core are pretty much what you're describing. Too much pressure causing hoses to leak, primarily around the area where they get clamped to something, or leaking gaskets around the water pump, or in some cases the water pump itself.

 

If it's the heater core it's pretty much the same deal as the radiator, only underneath the dashboard instead of in front of the engine. The heater core is just a little radiator with ducting designed to transfer the engines heat to air used to heat the cabin. It uses a similar design as a radiator, so it can be prone to the same issues.

 

Yeh, that's correct it's a manual one.

[New Subaru Fan]

Here's my update:

 

1) I removed the heat core from the system by simple short cutting (I just connected those two pipes coming from the main system using a short hose)

2) I tried to bleed the system, but there was only a little air coming out.

3) I went for a ride assuming there's no much air left but

she overheated again!

 

My observations:

 

- while bleeding the system the both upper and lower hose seemed to be pretty cool or just warm (the radiator fans were not on!): it looked to me there was no circulation through the radiator

 

- also the water level in the reservoir was almost constant even if I turned off and on the engine - the water was not sucked in as it should be!

 

- while revolving motor at higher rpms (over 3000) there were no bubbles coming out of the cooling system so I assume the head gaskets are ok

 

It's unbelievable: the only thing that I can consider as a problem for overheating is a water pump. But it was brand new as I installed it!

 

I know it's not easy to check whether the water pump is working properly. But are there any typical symptoms that would indicate a faulty water pump?

[Bdubs]

Well, if the water pump seized, you'd know it. It'd probably snap the timing belt, if not knock it right off. If it's brand new, I wouldn't question it, but if you have ruled out every possible source, return it and get another.

 

Not sure if this was mentioned above, I have ADD, and cannot possibly read that much small writing, but there is a weep hole in the water pump, and that may be why coolant was escaping from there, due to all the pressure.

 

The engine tends to have to be running fairly warm for the fans to kick on. Even if they weren't working, that wouldn't be causing the build up of that much pressure within your system.

[New Subaru Fan]

FINALLY SUCCESS!!!

 

After 4 days of struggle I figured it out. There was just a tough air pocket.

Apparently those older Legacies are meant to be bled under vacuum, because there's no air outlet valve on the radiator. My friend has a 1999 Legacy and the bleeding was not an issue at all because the air trapped in the cooling system was coming out freely as we were adding more coolant.

 

In my case I just lifted the right side of the car as much as I could, disconnected the upper radiator hose and turned it upwards. Then I turned on the engine and was slowly adding coolant until it appeared in the hose. Shortly after that the coolant started to come out of the radiator. Then I quickly connected the hose to the radiator. Although pretty pessimistic I decided to give her another go. She didn't overheat this time!!!!

 

And now my car is back and I can happily celebrate the New Year's Eve!

 

You have a good one too! Cheers

 

PS: By the way I'm driving without a thermostat now. Do you guys think it would be a good idea to keep it like that? This turbo engine tends to warm up very quickly even without a t-stat.

What are the pros and contras of not a having it?

[Bdubs]

Glad you fixed it. It just hit me that the 2.0GT is a FI engine, and bleeding the air out of those systems are a real pain. Next time, put the car on a steep incline to get the bubbles out easier.

 

You really should put the thermostat back in (which means having the fun of bleeding all over again). But, better safe than sorry.

[SBT]

Glad you fixed it. It just hit me that the 2.0GT is a FI engine, and bleeding the air out of those systems are a real pain. Next time, put the car on a steep incline to get the bubbles out easier.

 

You really should put the thermostat back in (which means having the fun of bleeding all over again). But, better safe than sorry.

 

It's the special 2.2T Legacy Sport (1st Gen) and yes bleeding the air is a pain if you don't do it right. First step is to get the top hose off.

 

And I agree, do put the thermostat back in. FI likes temps that are stable and no sense having cold and hot-ter spots in the block, when everything can be normalized.

[New Subaru Fan]

Yeh, finally the car runs well now! Thanks for your help in this matter. A thermostat is indeed important for a normally functioning engine. I found that it took for the engine ages to warm up without a t-stat.

And I'm also good at bleeding the air out now. I've recently added some radiator-flush into the system. It will hopefully remove all the rust and other crap.

Now having fixed this leakage problem I'm moving on to the other issues: check my recent topic 'My Legacy 1990 turbo 2.0 (manual) starts to jerk when I push her hard'. Maybe you can suggest a solution to this one. Cheers

[Matturbo36]

I have a similar problem with my 2005 GT. I've tried to bleed the system too many times to mention. I know I have an air pocket in the system since I installed a 146 degree tstat and it runs nice and cool for about 15-20 minutes then heats up to the stock temp of 176(?) or somewhere around there. Same syptoms, turn the heat and only ambient air pumps out for a while until the system decides to move the fluid. Any suggesstions aside from jacking the car up from the front? I drove my car up on import car ramps, is that enough of an angle?