I believe I have an air pocket in my cooling.

Cooling fan comes on but not when the gauge says but when the engine is hot. That is the gauge could read 3/4 but the fan won't come on. The fan comes on at idle (as usual) after I run at 2500 rpm for a couple minutes. This leads me to believe the gauge is not showing the engine temp but something else. The thermostat is hard to get to so I don't want to replace it. But when starting a cold engine after a few minutes the top radiator hose will get hot like normal when the thermostat opens.

I just now I removed the temp sensor which is above the thermostat. The coolant is at the top. I am going to drive it now to test it. Also I should say I put some stop-leak liquid in the system and this is when the gauge problem began(I should say the problem began when I drained the radiator). I backflushed the heater core for 15 solid minutes with a flush kit because I thought it was clogged. I don't think the system is clogged but your advice is golden to me. I also had drained the radiator before the stop leak so I could put in 4 qts of coolant and the 1/2 qt stopleak. The K&W stopleak I used does not require you to remove the thermostat or drain it out of the system after.

I know you may say to change the thermostat but please bear with me as I learn the hard way. Thanks

I just drove it 20 miles and reproduced the Gauge problem. The gauge goes high when after I drive at 55-65 mph and then sit and idle for a few minutes. The reaon I put Stopleak was to seal the radiator hose that would suck air as the engine cooled and leaked vacuum used to draw coolant in from the reservoir. Which would result in having to top off every day. I know the stopleak was a mistake and I am depressed about it but now I have to live with this new problem. A couple days ago I emailed the Stopleak company on how to dissolve the substance in their product. They responded promptly saying just water will dissolve it. I am thinking of backflushing the radiator can you give me some tips for this? How much flow to look for for example. Can you give me the way to test the thermostat in the car? What steps do I take and what to look for? Thanks

Can you tell me the steps for testing with a Temperature gun(I have one) Are these correct? 1) run engine until gauge says middle 2) Run at 2500 rpm then and check temp of lower hose every 15 seconds. (I notice the top hose was cold and then got hot very notcieably shouldn't I temperatur check the top hose?) Okay here's what I will do: Wait till top hose changes to hot then check the lower hose with my temp gun, is this right?I hope you understand I only used the stopleak as the last resort. This engine has three radiator hoses. Top, Bottom and one under the intake manifolds. I reclamped top and bot but to access the third hose you have to remove the intakes, this is beyond my skills.

For an acid flush do I take the radiator to a radiator shop? It has to be out of the car right?

Also, where do I click to add $$ to this question?
Thanks

Also, the problem seems to be a flow problem since at hiway speed the temp is normal. Only when I slow to idle does the gauge read hot.
The fans(both of them) were coming on and the reservoir was full so the car was truly overheating at idle. However the fans shut off before the gauge read normal.

I will test the thermostat opening temp after the car cools for a couple hours. I will email the Stopleak company again and ask again about clearing their sealant from the engine. Thanks

At the first response it only has Unfollow Flag Ask a Question Auto Parts Car Repair Manual. Previously I would click on Upgrade Question to put more $ in but I don't see that option now.

This is the message I sent them:

Hi thanks for your quick reply. I flushed the heater core and it seems clean now. I am having trouble now, the engine overheats at idle after a highway drive. This seems to be from an restriction in the cooling system. Can you tell me what will clear the blockage (your product) such as some chemical other than water. Your product won't clear with water as it is made to seal in water. Please help me to understand this.

Thanks Roy,

Pete

Yes I will have it flushed. Can they test it for blockages before it is removed from car? After?

Here's their answer:
Dear Pete;
There is no chemical that will help any blockage, except for water. I would suggest you remove some of the Fiberlock mixture by opening and draining it out of your block or siphoning. You can then refill will only water to dilute it. That should free any blockages.
Sincerely,

CRC Technical Support

Thanks, Pete

The radiator shop said they can't wash plastic/aluminum radiators. For a new one at AutoZone is $115. I will get it and install it and test it today. I will post the results later.
Also I checked the temps: at idle, Gauge at medium, the upper hose got hot 160 F while the lower stayed at 100F(car was not totally cooled down) The thermostat housing stayed around 140F but the inlet housing(where the Rad cap goes on opposite side of engine) was 182F(thermostat is a 180F in service manual) I did rpm 2500 for a minute and the lower hose got warm. I am using this info to OK the new radiator.
Thanks, Pete

Ok I put in the new radiator but am letting the engine cool down for a couple hours so I can add more coolant mix. I checked the temperatures and am a little confused. After driving 2 miles 750-3500 rpm the upper is 170F the lower is 140F the TS housing is 170F and the inlet housing is 190F. Could these be bad values, meaning a bad thermostat? Or are they normal? I take the avg of 3 measurments each time. I think the coolant flows from the engine to the upper hose through the radiator then the lower hose to the thermostat is this correct.

I am going to buy a thermostat, gasket, and O-ring just in case. How is it possible though for that stopleak stuff to make a thermostat not open correctly when the thermostat had been working fine? Is there an answer? I may be jumping the gun a little I will top off and test drive again. By the way this engine doesn't have the radiator cap on the radiator. I really don't know if I am skilled enough to change the Thermostat in this car. I have done it in my 1996 Ford Ranger and my 1996 Ford Aspire with competence. I pulled a junkyard thermostat housing off another Avalon and it seemed complicated.

Thanks, Pete

"Temps sound good" that's promising. I can wait to buy the thermostat until I top off and testdrive. As I was reading my e-manuals I realized that the "jiggle valve" on top of the thermostat could very well get clogged by the stopleak I used. Let's see how it goes.

FYI Mike from 2carpros sent me this message:

The donation upgrade option is available below the initial question. We will be fixing it so you can donate at any time. We really appreciate your donation. Thanks, Mike

Thanks

I just road tested, mini torture test(same as before), and the temp on the gauge moved less than 1/2 a gradation throughout various driving and idling tests. It started at a point 1/2 a graduation less than middle once warmed up.

So the radiator was restricted. Thanks for your help.

The temps I recorded now fixed are Upper 162F, Lower 148F, Inlet 175F, and TS Housing 175F.

Thanks for your help. I will donate some more when they allow the feature. Pete