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  #1  
Old 09-07-2014, 06:32 PM
svxcentric svxcentric is offline
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Overheating troubleshooting

Hey everyone. I'm looking for some help on troubleshooting a coolant system issue on my 97 SVX.

Symptopms:
I can travel as long as I like at highway speeds with stable coolant temperatures. As soon as I come off the highway or if I get stuck in stop and go traffic, the coolant temperature rises, sometimes just before the red line, and then drops back down again. It will do this 4 or 5 times and then will stablilze again.

I can delay or prevent the onset of these temperature changes by keeping the revs below 2000 rpm when crusing on the highway. This limits me to speeds around 60-65 mph

Actions taken:

At first I thought I might have a bad thermostat and I replaced that. The new thermostat had no effect. Since It was time for timing belt service anyway I had that done which of course included a new water pump. All parts were genuine Subaru, Again, no effect on the temperature changes. I also replaced the radiator cap. Again, same result.

I thought that maybe the system had not been purged of air properly so I bought a Lisle No-Spill funnel kit. I filled the funnel over halfway and also made sure there was coolant in the overflow. The heat was on - "Econ" with max temp and the fan on low. I was able to see that there were bubbles in the system coming up through the funnel and let the system purge for 25 mins at idle once the car came up to operating temperature. During that time I monitored the temperature remotely via a bluetooth OBD adapter and my Android tablet running the Torque app. The temperature never rose above 209 F and the fans operated as expected.

Results:

What I noticed is that even after 25 mins at idle, I still had small bubbles coming up every 5 seconds or so, three or four at a time. From my experience the system should have been completely purged of air by that point so I have to conclude that I have a leak in the system somewhere. The problem is that on visual inspection of all the hoses and the radiator, I can not see any leaks. No wet spots, nothing.

Likewise I would expect that if I had a leak in the heater core I would smell antifreeze in the cabin or see a leak. Neither of those things are the case.

By the way, the head gaskets are fine, at least for the time being. The car does not perform in any way like one with a head gasket leak would. There's plenty of power and there are no signs of coolant in the oil or any visible smoke in the exhaust.

So I'm left scratching my head about where to look next. I know I should have the radiator pressure tested, but as I've spent quite a bit on the car of late I want to eliminate stupid stuff like maybe loose hose connections or maybe some SVX quirk I don't know about before sending it to the shop again.

Has anyone had this issue or can anyone point me in the direction of a likely source of a coolant system leak so small that would let in air but not let coolant out at any significant rate?

Jim
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  #2  
Old 09-07-2014, 06:45 PM
92 SVX 92 SVX is offline
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Re: Overheating troubleshooting

Quote:
Originally Posted by svxcentric View Post
Hey everyone. I'm looking for some help on troubleshooting a coolant system issue on my 97 SVX.

Symptopms:
I can travel as long as I like at highway speeds with stable coolant temperatures. As soon as I come off the highway or if I get stuck in stop and go traffic, the coolant temperature rises, sometimes just before the red line, and then drops back down again. It will do this 4 or 5 times and then will stablilze again.

I can delay or prevent the onset of these temperature changes by keeping the revs below 2000 rpm when crusing on the highway. This limits me to speeds around 60-65 mph

Actions taken:

At first I thought I might have a bad thermostat and I replaced that. The new thermostat had no effect. Since It was time for timing belt service anyway I had that done which of course included a new water pump. All parts were genuine Subaru, Again, no effect on the temperature changes. I also replaced the radiator cap. Again, same result.

I thought that maybe the system had not been purged of air properly so I bought a Lisle No-Spill funnel kit. I filled the funnel over halfway and also made sure there was coolant in the overflow. The heat was on - "Econ" with max temp and the fan on low. I was able to see that there were bubbles in the system coming up through the funnel and let the system purge for 25 mins at idle once the car came up to operating temperature. During that time I monitored the temperature remotely via a bluetooth OBD adapter and my Android tablet running the Torque app. The temperature never rose above 209 F and the fans operated as expected.

Results:

What I noticed is that even after 25 mins at idle, I still had small bubbles coming up every 5 seconds or so, three or four at a time. From my experience the system should have been completely purged of air by that point so I have to conclude that I have a leak in the system somewhere. The problem is that on visual inspection of all the hoses and the radiator, I can not see any leaks. No wet spots, nothing.

Likewise I would expect that if I had a leak in the heater core I would smell antifreeze in the cabin or see a leak. Neither of those things are the case.

By the way, the head gaskets are fine, at least for the time being. The car does not perform in any way like one with a head gasket leak would. There's plenty of power and there are no signs of coolant in the oil or any visible smoke in the exhaust.

So I'm left scratching my head about where to look next. I know I should have the radiator pressure tested, but as I've spent quite a bit on the car of late I want to eliminate stupid stuff like maybe loose hose connections or maybe some SVX quirk I don't know about before sending it to the shop again.

Has anyone had this issue or can anyone point me in the direction of a likely source of a coolant system leak so small that would let in air but not let coolant out at any significant rate?

Jim
Its unfortunate but the likely hood is the headgasket is leaking, it doesn't leak water into the oil or water through to be burned, at least not yet, this appears to be a mild case that may run that way for 10k or more miles without affecting anything else.
What is most likely happening at this time is exhaust gases are slowly seeping into the water passages and those are causing the bubbles.
Your symptoms (getting hot after slowing down from highway speeds) are very consistent with our cars when they blow the headgasket.
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  #3  
Old 09-07-2014, 06:52 PM
Blacky Blacky is offline
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Re: Overheating troubleshooting

When operating, the cooling system is under pressure. No air could enter the system, only coolant could leak out.
There are test kits to check for exhaust gases entering the coolant. I would not rule out a head gasket issue just yet, although it sounds like it must be in it's very early stages of failure.
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  #4  
Old 09-07-2014, 07:59 PM
Tireiron Tireiron is offline
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Re: Overheating troubleshooting

I'm sorry to tell you, this is exhibiting the exact symptoms of a Subaru headgasket gone bad. As was stated, the bubbles rising are exhaust gasses being pushed from the combustion chamber into the coolant. You should pull over just when you get off the highway and take a look at the coolant bottle, you may see the bubbles there, you should also see the coolant level rise but not get drawn back into the system to the point where after a few trips it will overflow the bottle.

Here is a video from mine where you can see it bubbling violently in the coolant reservoir after a hard run.

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  #5  
Old 09-07-2014, 10:31 PM
1986nate 1986nate is offline
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Re: Overheating troubleshooting

This is signature SVX head gasket symptoms.
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  #6  
Old 10-07-2014, 03:58 PM
svxcentric svxcentric is offline
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Re: Overheating troubleshooting

**UPDATE**

Less than a week after having diagnosed my overheating issue as a blown head gasket, a long crack developed in the top of my radiator near the filler neck, This meant a new radiator regardless of what else needed to be done. Because of the symptoms I described and the failure of the radiator I began to suspect that the source of the problem might have been the radiator the whole time. I reasoned the crack that was now steaming had grown longer and wider over time, letting in more and more air, reducing the pressure in the system and causing the intermittent overheating (air bubbles).

I got the radiator and hoses replaced and haven't had the problem since. I've monitored my running temps and in regular driving coolant temp does not ever go over 208.4 F according to the ECU. The fans kick in at 203 F and a few seconds later it might go higher but then back down into the 190s.

I think that the fluid in the block tester kit I used may have been contaminated by some stray coolant being sucked into the tube, giving me a false reaction. To be honest the indicator fluid color changed from blue but not to bright yellow. It was a pale color change. It just goes to show that one should confirm any diagnosis that could result in a very expensive replair with more than one test.

Anyway, just in case it will help anyone needing to replace their radiator with a factory replacement, the going price from newenglandsubaruparts.com is $435. This is cheaper than subaruparts.com in Colorado, but if you're physically closer to CO, remember that suubaruparts.com has free shipping for orders over $50 so the price difference could be a wash. Since newenglandsubaruparts.com is in CT and I'm in NJ, the shipping was minimal. Also, I ordered on a Thursday, they shipped on a Friday and my order arrived Monday.

For anyone looking at the cheaper ebay radiators available from anywhere from $120-$150, the reviews are mixed to negative for durability on these. While they might be 1/3 the cost of a factory part, with stories about them lasting as little as 5000 miles it wasn't worth the risk for me.

Out of curiosity I priced the all aluminum radiator from PWR Performance. They do not keep them in stock. They have the plans and will build you one to order. Even though the company is in North Carolina the radiator will be fabricated in Australia. The radiator costs $735 and the shipping from Australia is $150. So if you want a hand made bullet-proof all aluminum radiator and you have $885 to spare, PWR will make you one. If you're building an SVX track racer with a high performance engine build, it might be worth it. If you're like me and your SVX mainly sticks to highways and byways, not so much. But now you know the price as of 2014.

Thanks to everyone for the advice and help, especially Tom (a.k.a. svxfiles) for answering my phone call, talking me through the options and generously offering to connect me with various folks and sources that might help with getting the engine work done. Luckily I don't need an expensive repair at this time but it's nice to know there is that kind of support out there for SVX owners.

Jim
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  #7  
Old 10-07-2014, 05:58 PM
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Conn SVX Conn SVX is offline
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Re: Overheating troubleshooting

My overheating was a bad radiator cap.
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  #8  
Old 10-07-2014, 07:37 PM
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Coan Coan is offline
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Re: Overheating troubleshooting

Good to hear it was relatively minor! My '95 that I recently picked up was exhibiting this same behavior, and it too ended up being a cracked radiator. Seems like any leak in the system will behave this way, be it a radiator, cap, or head gasket etc.

For what it's worth, when the radiator cracked in my '97 I replaced it with a Silla radiator from eBay (around $115 shipped IIRC). It's been 5 years and almost 20k miles without issue thus far.
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  #9  
Old 10-08-2014, 03:14 AM
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SVX92-97 SVX92-97 is offline
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Re: Overheating troubleshooting

Great News! Wish I was that lucky Keep your fingers crossed and hope that was your real issue the whole time.
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