What is this? (pic)
 

Ok so yesterday I pulled the old thermostat out and was cleaning the housing and saw this red rubber - ish gasket inside the housing. What is it and what should I do? The other pic is the old TS (top) with the gasket still intact and the new TS on the bottom, which I am returning for a refund and getting an OEM TS b/c they are obviously not the same. I see no leaks or evidence of any problem on the outside of the housing, hoses, etc. Thanks in advance. '99 4Runner Limited 3.4L V6 190k miles
Thanks in advance.



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I'd say gasket maker for good luck perhaps on a previous install. FSM says clock the jiggle valve to 6, OEM is much better quality. I found corrosion on my T-stat housing flange needed a bit of JB weld to smooth it out for a better seal, so far so good.

Sooo, what do I need to do? Have this thing towed to a shop or just put the new TS in and see what happens?

I would put the old t-stat & gasket back in, return the non-OEM, and get a OEM replacement like you planned.

^^ That is what it looks like to me.

If your thermostat housing is not too corroded, the rubber thermostat gasket should be all that is needed to create a good seal.

If you are going with an OEM thermostat (good choice!) I would also consider replacing the original rubber gasket while you are in there.

:safari:

thanks for the replies so far...so I replaced with an OEM TS and gasket but I still have a problem...the temp gauge crept up slowly but stayed slight above normal but here's the weird thing...the top radiator hose got super hot and the bottom stayed cool to touch. Same thing as before I replaced the TS. Also there's a clicking noise coming from a very small black box under the hood that is positioned behind the steering wheel...i think it has a green tag on it that says "vacuum"...? I've never heard that noise before.

1) shouldn't the rad hoses both be warm/hot?
2) Since TS and gasket are both brand new OEM, what else can be the problem?
3) Can the clicking noise be part of the issue?
4) what the heck do i do now?

1. The T-stat will open and close accordingly, hot water will come from the motor and cool water will enter the motor after it has cooled down going through Rad.
2. What is the problem
3. Clicking is normal, you emissions systems is working as it should.
4. Enjoy, drive off into the sunset, keep an eye on your fluid levels occasionally, your temp gauge is not very accurate, as long as it is close to the middle your good, if not wash AC condenser and rad out.
5. You might consider changing the rad incase it hasn't been done to avoid the Strawberry milkshake syndrome.

Forgot to mention that the heater is still not working and that top rad hose is BLAZING hoot and the bottom hose is cool. My gut tells me this is not normal. Now what?

-new rad cao
-new OEM TS and gasket
-new Coolant and bled properly with no more air bubbles coming out

Plugged heater core would be a good thing to mention as your problem, Make sure your Climate control system is operating properly and that you are switching to hot air but not getting hot air, The Limited Climate control system has a 99% failure rate.. if it is switching over but not heat then I would disconnect the lines going to the heater core at the firewall under the hood, figure out a way to hook up a garden hose and start flushing. How long have you been without heat, and I thought you already decided to buy a new OEM T-stat and changed it? if not maybe finish that. Could alway throw the old T-stat in a pot of hot water with a thermometer and see when it opens and that it opens fully. But if your unsure of the maintenance I would go ahead and flush that Heater core, replace the Rad, T-Stat, and fluids.

you are correct. I already replaced the TS, gasket, fluids and assured the heater control valve is working properly and it is. I live in Tampa Florida so I have no idea how long heat hasn't worked b/c I rarely use it. I'll try the flush and report back. Thanks so much!

EDIT/RECAP:
So my 4runner was overheating and I saw green fluid on the left side of the engine only. I couldn't find a leak or anything loose so I dumped some K-seal in, replaced the old TS with an OEM TS, gasket, new fluids and burped/bleed the system with a funnel in the rad , while it was running at a slight incline. It bubbled a bit then stopped but I had to turn off the 4Runner b/c the fluid was slowly creeping up the funnel and about to spill over. The reservoir is about 1/4 full. I also replaced the rad cap. But it's still trying to overheat and the top radiator hose got super, super hot and the bottom stayed cool to touch. I turned off the ignition before it got too hot. I've done this procedure several times just to make sure I got all the air out but it still continues to overheat and no heat inside.

The heater control valve works/moves fine. There is 2.5 gallons of fluid at proper water/fluid ratio as that is what the manual indicates. To get the fluid in the block I had to let it cool, pull off the top hose and dump the additional gallon in that way as the rad wouldn't accept the entire 2.5 gallons, even while running it.
1999 Toyota 4 Runner Limited, 190k miles.

1) shouldn't the rad hoses both be warm/hot?
2) Since TS and gasket are both brand new OEM, what else can be the problem?
3) what the heck do i do now? Flush heater core even tho both heater hoses going into firewall are warm?
4) I still have no heat and it engine is still overheating. Not that it matters b/c I live in Florida but I suspect no heat is telling me there's a problem somewhere.
5) All of this was done w/heat turned to hot setting


Thanks in advance.

Because you mentioned using k-seal and the overheating problem persists (does the temp gauge go near red?), it looks like the sealing additives may have clogged areas in your cooling system that shouldnt clog.

Oh boy.

Sounds to me like it's time for a replacement radiator. Super hot on top and cool on the bottom indicates limited (or no) coolant flow thru the radiator. Also,you mention that the coolant slowly rises in the funnel that you put into the radiator fill hole. Again, I would say replace the radiator (from $80 up).

When replacing the thermostat, did you place the jiggle valve of the new thermostat in the 6 o'clock position as mentioned by Malcolm?

When doing a drain/refill or a flush of the cooling system, drain the rad then fill first with distilled water and turn on the engine and the front and rear heaters so the coolant in both heaters are replaced, check the temp and after 10 minutes, shut off the engine then drain and fill with distilled water. At this time, do not close the radiator cap. Repeat the process until the drained distilled water is clean. Fill with coolant. Keep the radiator uncapped then jack up the front and turn on the engine and heaters to let the air in the system burp out. Watch the radiator filling neck until no air comes out then close the radiator cap.

HTH