Non Subaru thermostat for an SVX?

[Chucksta]

Just like the title says, I'm looking for a thermostat from someone OTHER than Subaru to put in a 97 SVX..

Why? Since I've owned it, it's always been quick to warm up, and the temp stayed dead stable at just under half. Recently, that changed. She seemed slower to warm up, and sometimes the gauge would actually drop. I bought a brand new thermostat from the local dealership, and installed it. The old one showed signs of rubbing on one side, so I figured I would be good to go.

Not quite so lucky, it would seem. Although it's now quicker to start to get warm, just barely into the operating range is the highest it goes when moving. In stop and go traffic, it slowly climbs, but as soon as I start moving with any speed, it drops like a rock back to just at the bottom of the operating range.

My mechanics opinion is that, although it's from Subaru, that doesn't necessarily mean that it's from the same manufacturer as the original, and as such, may have a lower "crack open" point. He liked the idea of finding a different one from ( hopefully ) a different manufacturer. My other option would be cardboard in front of the radiator, or , since it's got a black bra, black duct tape over the air inlet... I'd rather not go there..

[processengr]

This could be a temperature sending unit problem as well...

[NiftySVX]

The opening temperature of your thermostat is not going to cause that kind of problem. It should have said on the part what the temp is. I would make sure that the gasket for the thermostat is completely on it and installed correctly. The Tstat goes inside the seal, it fits on it. Not in front or behind it. An improperly installed or missing gasket can cause a problem like this. The bleeder also needs to face up.

I can promise you the unit is the same. There aren't very many different kinds and the difference isn't that great. I wonder if you filled the engine correctly. I have seen that a lot and it will cause your symptoms and is really just asking for major engine damage. If the system doesn't pressurize you need to get the air out and hope you didn't damage it.

You can get a different one if you want but if you get a good quality one it will probably be made by the supplier subaru uses, or to their specification.

[Tapani]

If you let the engine idle with the HVAC set to "econ" do the fans come on after a while and then switch off? If yes, then the coolant exit temp is fine.

This does not say you do not have air in the system :-), though.

I know I repeat myself, but get Evoscan or Ecutuner - you can monitor the engine temp - the ECU has a separate sensor (from the gauge).

Another possibility is to measure the temp at the coolant exit X-over - where the temp senders are with a contactless thermometer. The metal temp is within 1-2 degrees C compared to what the ECU sees (at least on my car).

I suspect the sensor too - crept out of range. BTW, there's almost a 30 degree C dead zone in the gauge at the horizontal position....

The Subaru thermostate is very well built and it has a wide opening and operating range. It is not on/off.

Tapani

[ensteele]

I would be careful using anything but Subaru Parts.

[Chucksta]

Gonna do this in Word, because, for the second time, I’ve lost everything I’ve typed. First time, when I hit “submit”, I got a page saying I couldn’t as I was already logged in and had posted. I copied and pasted to Word, re-opened the browser, logged into the site, pasted and posted… Damn it … I SAW the post .. Now… Nothing …WTF?? And again I just watched ten minutes of typing go back to a blank “reply to post” box mysteriously empty.. So, excuse the font, but I’m hitting “save” this time, BEFORE I copy and paste..

Anyways, Let’s get at it…

I don’t think it’s the gauge. The response is very linear since before this problem started. It took an appropriate time to warm up, and, the air temperature from the vents matched the gauge. The rad hoses feel about right for what the gauge shows. There’s no wild swings in the displayed temperatures. Exactly the opposite, It gets warmer and warmer if I sit at a light, or get stuck waiting for a couple of lights waiting to make a left. As soon as I start rolling, the temperature gauge starts dropping, and it never drops below a very, very, very specific point.

So… why does the font change in the next paragraph? No idea..LOL… but at least it didn’t disappear..

“It should have said on the part what the temp is.”.. Yup, it may well have, but never even occurred to me to even look. I purchased the replacement at the local Subaru dealership. I asked if there was more than one listed ( as in summer and winter), and was told “no” The box simply had a part code on it.

“The Tstat goes inside the seal, it fits on it. Not in front or behind it. An improperly installed or missing gasket can cause a problem like this.” When I put it in, I “used the force”.. I did it by feel, not by sight. I went with the assumption that, if it wasn’t leaking when I was done, it was O.K.. All I can say is that it felt like it was seating into the O ring and flat in the housing when I put it in, and the inlet housing seated flush before I put the bolts back in.

“The bleeder also needs to face up.” O.K…. Now I’m really starting to feel like a dumb-ass.. I searched this site to see what was involved in changing it, and, where it was. If that info was there, I missed it. I’m not doubting that it needs to have the bleeder pointing up, but I definitely didn’t see an arrow on it or any other indication. If you would be so kind as to explain why, I’d really like to know the physics behind that. As it is, even trying to figure out how the thermostat could even function in that configuration stumps me. I’ve never seen a thermostat anywhere else other than at the top of the engine, with coolant flowing from the engine over the coil and then through the rad. Theoretically, the thermostat sits in coolant at the bottom of the engine in it’s housing, seeing the coolant heated by the engine mixed with whatever coolant from the bottom of the rad that comes through the bleeder orifice. The coolant could be coming out of the engine boiling and then be cooled enough to not even open the thermostat by the time it passes through the radiator, especially at sub-zero ambient temperatures at highway speed..The more I think about it, the less I obviously know…

“I wonder if you filled the engine correctly”.. That one, I didn’t really worry about. The rad was full before I started, and the reservoir was at the correct level. I only managed to miss the catch pan with about three ounces when I drained the system. When it was all buttoned up again, I filled the rad and started her up. When the temp gauge started to move, I was getting cold air out of the vents. I went to 2500 RPM for about twenty seconds, and started to get warm air. The rest of the coolant went in at that point, and the amount that I had to add to top it off was pretty much equal to what I spilled. So, from that, I really didn’t feel that an air pocket was an issue. There have been three hot / cold cycles since I put the thermostat in, enough for the reservoir to cycle any pockets out. The upper rad hose agrees with temp gauge, by feel. It gets hotter as the gauge rises ( as it will do when not moving ).

“If you let the engine idle with the HVAC set to "econ" do the fans come on after a while and then switch off? If yes, then the coolant exit temp is fine.” Can’t tell.. I let it run for over half an hour, it got to about 1/3 and stopped there. Interior warm , HVAC set to econ, low fan. It’s just too cold here, or it’s gonna need a less windy day and more time.


“I know I repeat myself, but get Evoscan or Ecutuner - you can monitor the engine temp - the ECU has a separate sensor (from the gauge).” Are those specific devices, or are they brand names for an OBD2 code reader? I have an Innova code reader with a feature called “Live Data” Would that pull it’s info from the same source as the Evoscan or Ecutuner you mentioned?

“Another possibility is to measure the temp at the coolant exit X-over - where the temp senders are with a contactless thermometer.” I have an infrared temp sensor somewhere in my RC toolbox. Now I’ll have to find it and put it to use.

“The Subaru thermostate is very well built and it has a wide opening and operating range. It is not on/off.” That’s the part I don’t get.. Traditionally, a 180 thermostat should crack open at about 160 and be fully open at it’s rated temperature of 180. But, when it’s located at the bottom of the engine, with coolant that has passed through the rad coming in through the bleeder orifice, I now realize it may have some different operating “characteristics”..


It would seem at this point, that it’s time to find a hoist somewhere warm ( it’s freekin’ cold here for the next week, at least), pull it out, check the O ring placement, put it back in with the bleeder facing the top of the engine and see if that makes a difference. First, I’ll try and reconcile, ( with some of your great suggestions), if the temp gauge is in sync with the actual engine temp.

The only thing I’ve done to the cooling system since I bought it last fall was add 1/6 of a bottle of “Rislone Liquid Copper” stop leak. I was losing about an ounce of coolant every thousand miles, and couldn’t see where from.

Score :

SVX and it’s cooling system idiosyncrasies….1

Chuck……………………………………………………………..0

[NiftySVX]

The thermostat has a small little doomahicker on the flat part of it. It is a little dangly guy. That is the air bleeder. It allows any air trapped to come through it as well as a little bit of coolant. It sort of looks like an um…body piercing.

A quick search yielded a few pics. One is an aftermarket unit but shows the temp on there. The other shows a correctly installed gasket around the thermostat. It also shows positioning of the bleeder.

You can have an air bubble that displaces only a few fluid ounces of coolant behind the thermostat to cause a malfunction or in a head to crack it.

The fact that you mentioned the heater core had air in it proves there was air in the system. These can be tricky to fill. You can't just pour coolant in it and close the cap and move on with your day. It can be done by removing the upper radiator hose and pouring coolant in it but the best way to do it is with a spill free funnel.

Winter and summer thermostats have not been in use for many, many years. You can put whatever temp thermostat in the car you want and it will only change the time it is opening and closing. The cooling system is designed to operate at a specific temp and it made to do so by specific specs and a thermostatically controlled three speed cooling fan system.

I don't remember seeing if you answered the question about the hoses being pressurized. The fact that the hoses show a temperature difference doesn't mean much to you unless you've put stop leak in it or your radiator is clogged.

If the hoses don't feel firm when you squeeze them after the engine has been run for 5-10 minutes then it isn't pressurizing and you either have a bad cap or an air bubble. You can drive it for 25 years and not get the air out of it. I have seen this many, many times on Subarus.

I promise you there is air in your cooling system. If this problem only surfaced after you replaced the thermostat, I would bet you the cost of a plane ticket to wherever you are that I could fix it with coolant and a funnel. Also, I hope you used genuine subaru coolant mixed 50/50 with distilled water.

Edit: also, the coolant does not flow against the thermostat. It works the same as any car. The only difference between having a thermostat at the top and having it at the bottom is the placement of it. Could be the top hose is in to the rad, could be the hose is out. Just depends on where the engineers put the thermostat. Doesn't change the cooling capacity of the radiator or the design of the system

Some more edit: You don't need to be measuring temps. Unless you put stop leak in it or something like that you don't have that problem.

[steamer99]

Looking at the FSM (see attached pictures) there is a good illustration of the correct way to install the thermostat gasket (cooling system1).

Originally Posted by NiftySVX

Edit: also, the coolant does not flow against the thermostat. It works the same as any car. The only difference between having a thermostat at the top and having it at the bottom is the placement of it. Could be the top hose is in to the rad, could be the hose is out. Just depends on where the engineers put the thermostat. Doesn't change the cooling capacity of the radiator or the design of the system

I hate to disagree with someone with a lot of experience but according to the FSM (cooling system2) the top hose is to the rad and therefore seems to be backwards, as the thermostat is at the outlet of the rad, and the inlet to the pump. It also shows why it will not work unless the spring (sensing element) is toward the engine. Air anywhere in the system will cause issues, and as I understand it one of the best ways (other than the one described by Nifty) is to raise the the front of the car fill the rad, start the engine with the rad cap off and top it up once the thermostat opens and the level drops.

[Chucksta]

Well, This is getting weirder by the second...

"The fact that you mentioned the heater core had air in it proves there was air in the system. These can be tricky to fill. You can't just pour coolant in it and close the cap and move on with your day."
Umm.. I didn't do that.. I let it circulate, THEN added the rest of what was taken out, plus probably an ounce or two more, then put the cap on. If anything, there's actually more coolant circulating in the system there was before. Also, I used to get a rumbling from under the dash on a warm re-start. I haven't heard that in the last little while, not since the temperature thing started rearing it's ugly head. For sure I haven't hear the rumble since I changed the thermostat.

The low temperature readings where why I changed the thermostat. I changed it and it got worse....

The upper rad hose has definitely got pressure when hot..



Still don't know if an "Evoscan or UCUtuner" is the same as an OBD code reader, but, as "Timpani" states, the ECU doesn't use the same sensor as the gauge..

I'm going to plug in my reader and go for a boot.. I'll see what the readings are and post back in a bit..

[NiftySVX]

He's right the coolant fans and the engine temperature sensor are different.

Has the thing ever had any stop leak or anything like that in it?

[NiftySVX]

Originally Posted by steamer99

Looking at the FSM (see attached pictures) there is a good illustration of the correct way to install the thermostat gasket (cooling system1).




I hate to disagree with someone with a lot of experience but according to the FSM (cooling system2) the top hose is to the rad and therefore seems to be backwards, as the thermostat is at the outlet of the rad, and the inlet to the pump. It also shows why it will not work unless the spring (sensing element) is toward the engine. Air anywhere in the system will cause issues, and as I understand it one of the best ways (other than the one described by Nifty) is to raise the the front of the car fill the rad, start the engine with the rad cap off and top it up once the thermostat opens and the level drops.

How are we disagreeing? I agree with everything you said. Especially the elevating the front thing. Done that many times! I usually leave it running though, and I massage the hoses to get anything out. Just about the only way to get the air out of the heater core on a 07 ish camry. It is confusing. We are all thinking the same thing but are getting lost in the words. What I was trying to say is that it doesn't matter if the tstat is at the top or bottom of the engine, it doesn't matter if the coolant inlet is at the top or at the bottom, it is all the same.

I am confused myself! Let me try and be a little clearer. Despite what the diagram or whatnot would imply, there is not "hot" coolant on the "wrong" side of it. The water pump has the bypass pipes that circulate coolant when the tstat is closed. So we have that hot coolant going around in the engine with the radiator sys out of the loop for all intents and purposes. Then, the thermostat opens. The coolant is now circulated past the tstat and across the radiator. EDIT: Don't pay attention to the order of what I said about radiator and tstat here. It doesn't matter. And again, coolant can flow past a tstat either direction, different designs exist.

Edit some more: look at the design of the block and the water pump in your picture (I don't have mine here so I can't comment on it specifically) And it will make sense to ya. IIRC the coolant flows from bottom (where the pump is located) to the top of the block, thru the crossover pipe, into the top hose, then to the bottom hose past the tstat if it is open. If it isn't then it doesn't flow past it. The coolant is staying on the back side of the pump.

[Tapani]

There's actually a big difference in the thermostat location.

If it's in the upper hose it controls the coolant engine exit temperature. If it's where it is in Subaru flats, Porsche liquid cooled engines, Toyota Supras and many other high performance engines it controls the coolant engine inlet temperature. The "signal" comes from the bypass flows - x-over bypass, heater core, oil heater (if equipped). That's why the thermostat seems to be installed "backwards". Cold coolant is mixed to the bypass flows to get disered inlet temp.

The delta T across the engine (cooling circuit) is designed to be very low, this requires a high flow rate - and a flimsy looking radiator :-).... these are basic design features in our system - and also the cause of the very long discussion in the famous cooling again and again thread elsewhere on the forum. The stock system is very carefully balanced as it is, including the rather funny rad fan control scheme (engine exit temp).

I trust you either have bad sensor or air in your system. The bleeder nipple in the thermostat is important - make sure it points up. The reason: Gravity.

I did not realize your car is OBDII - the Ecutuner is out. I trust the Evoscan does work on your car, but it need a different cable (from mine). These both are diagnostic software - you can hook up a laptop to your diagnostic port and monitor all accessible engine and tranny parameters.

Kind regards,

Tapani

[NiftySVX]

Originally Posted by Tapani

There's actually a big difference in the thermostat location.

If it's in the upper hose it controls the coolant engine exit temperature. If it's where it is in Subaru flats, Porsche liquid cooled engines, Toyota Supras and many other high performance engines it controls the coolant engine inlet temperature. The "signal" comes from the bypass flows - x-over bypass, heater core, oil heater (if equipped). That's why the thermostat seems to be installed "backwards". Cold coolant is mixed to the bypass flows to get disered inlet temp.

The delta T across the engine (cooling circuit) is designed to be very low, this requires a high flow rate - and a flimsy looking radiator :-).... these are basic design features in our system - and also the cause of the very long discussion in the famous cooling again and again thread elsewhere on the forum. The stock system is very carefully balanced as it is, including the rather funny rad fan control scheme (engine exit temp).

I trust you either have bad sensor or air in your system. The bleeder nipple in the thermostat is important - make sure it points up. The reason: Gravity.

I did not realize your car is OBDII - the Ecutuner is out. I trust the Evoscan does work on your car, but it need a different cable (from mine). These both are diagnostic software - you can hook up a laptop to your diagnostic port and monitor all accessible engine and tranny parameters.

Kind regards,

Tapani

He said it better. I was trying to be more general and describe the basic operation of the system. (It doesn't matter meaning the coolant system still works by using a thermostat to keep coolant in the engine and not going thru the rad)Note what he said about the bleeder.

[Chucksta]

So.. According to the "Live Data" function on my ODB2 reader...

It's a bad temp sensor ( the one for the gauge ). The starting reading on the meter was pretty close to ambient temperature. The dash gauge didn't even budge until 140 F. The lowest edge of the operation zone clocked in at 160 F. It's "I'll never fall below this point once I'm warm" point, located at just less than two needle thicknesses into the operating zone, was 180 F.

Some probably less than judicious application of throttle, followed by parking nose against a building, out of the wind, got fans on at 202 F, with the dash gauge showing just under half, just a bit lower than where it sat and never budged from, before this started a couple of weeks ago. The fans came off at 190 F.

Would the sensor be sensitive to anti freeze additives? Does it actually contact the anti - freeze? As in could a contaminant cause them to malfunction? There's about 1/6 of a bottle of "Rislone Liquid Copper " rad sealant in the system. I couldn't find my mysterious one ounce per thousand mile coolant loss source that it's had since day 1. I git tired of trying to find the source of the loss, and put it in the system.. The funky gauge readings began around the same time it was put in, but just before, or just after, I can't recall.

The worst part of this? Before, the gauge was lying to me ... AKA.. "The SVX temp gauge dead zone" Now, it accurately reflects the actual changes in coolant temperature, but with horrendously poor calibration. Do I replace the sending unit and return to oblivious happiness as the gauge always sits where it's supposed to ? Or, leave it as it is ( assuming the sensor doesn't get any "worse"), as I now know what temps are being shown at what needle position, it's actually an improvement... well sort of..

[NiftySVX]

Remember how I asked about stop leak additives? Yes it will effect it. That stuff is bad. Real bad. Never use it. Ever. Ever. Ever. You need to replace that sensor, and flush that stuff out of the coolant. I wouldn't be surprised if the sensing element had a layer of that stuff on it.