33 replies to this topic

[podmak]

Hi all, 

 

the car is a 1995 Subaru BG5 - twin turbo ej20 - Liberty GT Sedan

 

 

 

Problem: No hot air out of cabin vents. Bottom (lower) radiator hose doesn't warm up. 

 

Notable fact: The car does not overheat when driven. 

 

 

What I did already: 

1. I checked the thermostat, replaced it with a genuine Subaru part. Boiled it prior to installing it, it works fine. 

2. Removed radiator and flushed it. It doesn't seem to be clogged, the flow seems to be 1:1 - as far as I was able to observe. I took it out, pumped water to the top opening and the water came out nicely from the bottom opening. 

3. Replaced radiator cap - new genuine part. 

4. Cooling system pressure test revealed no leaks.

 

 

I have not seen the passenger side radiator fan come on - ever. Only the driver side fan comes on once the car heats up - and then stays on infinitely. But there is no hot air coming out of the vents. 

 

I believe I bled the cooling system properly - I raised the front of the car up. Filled through the radiator filler all the way to full, then put on the cap. 

 

I then filled through turbo tank, started the engine, put heating temperature inside to max, A/C off, fan to min... 

 

I massaged both the top and bottom radiator hoses until there were no more bubbles coming out. And filled the turbo tank as required. 

 

 

 

But still - no hot air inside the vents, and the bottom radiator hose doesn't get warm. I heard some other members of the forum saying it's meant to be cooler than the top hose. I agree, but the top radiator hose is boiling hot, and the bottom is dead cold. The bottom radiator hose should be warmer - much warmer that this. (engine working temperature)

 

Also the driver's side of the radiator is boiling hot, and the radiator cap itself is very cool.

 

I know, this could be something as simple as clogged heating core - it wouldn't bother me - but how can I be sure? The lower radiator hose is what worries me - along with the fan that only comes on and never turns off. 

 

At this point I am open to hearing all the opinions - what else should I try? Also please feel free to comment on something as obvious as "that's normal Subaru behavior", I've only had the car for a very short time, and it's all very new to me. 

 

Thank you in advance for all your input. 

[duncanm]

If you're worried the heater core may be blocked - bypass that then restart the diagnosis on the important bits of the system.

 

A suby heater core should always have water flowing through it, regardless of state of HVAC controls.

[podmak]

If you're worried the heater core may be blocked - bypass that then restart the diagnosis on the important bits of the system.

 

A suby heater core should always have water flowing through it, regardless of state of HVAC controls.

 

Aha! 

 

So if the heater core is blocked, it prevents the coolant from properly flowing through the system; That would explain the lower hose being cold all the time. (?)

[duncanm]

Yes, but.

 

Not all the coolant flow is pushed through the heater core - just some of it.

 

I'm just suggesting that you should bypass the heater core if its suss, then proceed with your diagnosis of the other parts of the system.

[podmak]

Thank you.

 

I bypassed the heater core; it seem to have resolved the problem temporarily. Immediately after I put everything back together, I bled the system and the lower radiator hose heated up properly, the fan started to cycle correctly and for a while the problem seemed to have been solved.

 

Unfortunately it didn't last very long. I went for a longer drive the following day and when I came back, I was parking the car in garage and noticed the fan was on uninterupted. I touched the lower radiator hose and it was really cool.

 

So now, I am wondering; If it was working the day it was fixed, but is no longer working now, there must be a way for air to have found its way into the cooling system. And since pressure test doesn't show any pressure loss when testing, this leaves me with only one possible cause of my problems.

 

Thoughts, anyone - please?

[podmak]

Yes, but.

 

Not all the coolant flow is pushed through the heater core - just some of it.

 

I'm just suggesting that you should bypass the heater core if its suss, then proceed with your diagnosis of the other parts of the system.

 

And duncan, since you're the only one responding here, am I missing anything else out of my cooling system troubleshooting list please?

 

1. Radiator - I've had it out, I flushed it, the flow seems to be flawless.

2. Thermostat - new; cooked prior to installing, opening/closing with no probs.

3. Heater core - bypassed.

4. Pressure test - holds pressure -> according to the mechanic. (I don't have a pressure tester) (So I am assuming the turbo tank/radiator caps are not a problem either)

 

Thanks again.

[duncanm]

I'm not really an expert here.

 

It sounds a lot like an air lock / bubble in the system.

 

Is your radiator cap ok, plenty of coolant in the overflow bottle and the overflow hose down to the bottom of it?  When cooling down, the header tank radiator cap should suck any expelled coolant back in from the overflow bottle. If the cap is busted, line has a hole in it, or no coolant in the bottle, then it'll suck in air.  Not sure about the BG5 - if you have a cap on the radiator itself, I think it should be a sealing non-springy type, so it doesn't try to vent or suck in - that's the job of the header tank cap.

 

When you say the radiator cap is cold -- are you talking about the header tank?  That should be quite hot - as its where all the turbo cooling flow ends up (so that when you stop the engine, it keeps circulating through the turbos via convection).  Maybe check coolant is flowing through those ok (all those metal lines and hoses on top of manifold leading to header tank should be hot).

 

Guys - chime in. Someone here knows more than me about this stuff.

[podmak]

Still appreciate it; it is true I replaced the radiator cap recently; now the new cap is written to have to withstand pressure of 109kPa - is this correct please? If anyone could comment on this;

And yes duncan I meant the radiator cap; the header tank (turbo tank) is hot; just like the upper radiator hose;

Also yes there is enough coolant in the overflow tank, and both of the overflow hoses are submerged all te way;

Again, I really appreciate your help; thank you.

[podmak]

Update:

 

I took out the thermostat - car runs fine. Fan cycles properly. Lower hose heats up, no overheating, no problems. 

 

I cooked the thermostat again, just to rule it out - it seems to be opening/closing without any issues.

 

 

It's weird it works in the cooking pot, but doesn't work inside the water pump.

 

 

I have a theory, if anyone cares to comment, you are welcome to do so (please!).

 

 

 

The "return pipe" that is coming from the back of the engine block is blocked. There are 3 water outlets on the water pump housing. 1 is for the lower radiator hose - this is where the thermostat sits,

 

Then on side, there are  2 additioanl outlets. 1 of these is the "return pipe" and the other one is I don't know. These two hoses are bringing the water from the back (and elsewhere) of the engine to thermostat, and the water flows directly onto the thermostat's spring - that's how the thermostat knows when to open; It's being awashed by the incoming hot water from the block/etc.

 

And I think that these two, or at least one of the pipes is clogged.

 

 

I am really only just fantasizing here, and would love someone to shed more light on the issue.

 

 

I will run without the thermostat for the time being. But it sure bugs me.

[CodeBurn3r]

one inlet is the bypass hose the other is for the OIl Cooler/Warmer haha

[duncanm]

double check the thermostat is genuine / the right one / installed correctly.

[acres]

Stick a thermometer in the pot and check the thermostat is actually opening at the correct temp.
And also make sure it is actually opening all the way.

[Adam]

Just buy a new thermostat. They are like 20 bucks

[podmak]

Can you tell from the images the thermostat is working fine?

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[RX25SE]

Are the heater hoses to the heater core both hot when the engine is warmed up?

 

Are you sure the temp gauge on the dash is accurate?

 

 

 

All the symptoms sound like a dodgy water pump (corroded impellor) or except for the fact it doesn't overheat.

 

 

Weird.

[CodeBurn3r]

This might be common knowledge but make sure you fit the thermostat with the little hole thing at the top.
Also, just pull the hoses of the block and pump some water through them.. Also make sure they flow the correct way.. I think it causes an issue if they are mixed up.. Aka in is connected to out

[acres]

It's a bit hard to tell in that bottom pic but are you sure that thermostat is opening all the way? And what was the final temp when it was open all the way?

 

I would think that if the problem went away with the thermostat removed, than it is most likely the cause of the problem. 

[podmak]

.

[podmak]

With regards to the faulty waterpump - wouldn't the car overheat?

With regards to the temp gauge - How can I make sure it works properly; it behaves normally, just like any other of my previous skoda, suzuki, bmw, subaru and subaru.

With regards to the thermostat - yes it opens all the way; There is no need to drill into it; tstat is a simple thing and this particular works;

I've had the car sent to a subaru mechanic; I spoke to him about it and he mentioned that there may be a blockge when the thermostat is inside the pump housing;

He hasn't had a chance to check it thoroughly yet, but when he does I will make sure to share with people here.

Thanks all for their constructive feedback, much appreciated.