Coolant Leak Dripping from thermostat
 

Hey everyone, new poster but long time researcher since everyone here seems to have great knowledge. So I searched before I posted this to avoid duplicate posts.

So here's the background story, driving to work, my 97 ES300 overheats and steam is coming from the engine block. Pull over, oil dipstick is not white (no bhg..aka blown head gasket), so I put water and it's fine. Driving home, she steams out again; same situation, reservoir is full, oil is clean but coolant is steaming and it looks like it's coming from the thermostat. Put water in again, was able to drive it home (10 miles of refilling water).
Well the final refilling, water is pouring out of her, so I figure the thermostat housing gasket probably disintegrated. :cry:
I've replaced the thermostat, the gasket and the o-ring on the metal water inlet pipe just before the t-stat.
Well, it had the same leak while I was putting in new coolant and it appears to be coming from the general area of the thermostat but slightly above it. There seems to be no other leaks and the water pump appears to be functioning because the temperature rise is linear and predictable, the radiator is good shape and holds coolant. I'm perplexed as to what it may be.
Oh, I'm not a newbie, but I'm also not the guy that rebuild his transmission in a day (because I've never done it). I have the majority of the basic tools and hopefully I can get this car back up before the end of the weekend. Thank you!

Did you torque the three bolts to the thermostat housing? Quite possible you have an uneven seal that is causing the leak...

Check your central rubber coolant hose. It's located right under the intake manifold and is very close to the thermostat, which can be misleading. You would be the third or fourth person with this type of leak on this forum, if I'm right on the diagnosis. With the age of your car, the chances of this happening are very high.

Did you drive it around at speed for a while to see how it behaves or just idle the engine?

It does drive and yes it wound up being the bypass hose. I'm still wondering why Toyota would design a rubber hose under all of that...so should I go braided steel or the same thing? :uh:

Thanks for all the help guys! This is going to be a fun project!

Get the same hose from the dealer - only place to get one.

Actually, I bought the hose from Napa Autoparts. It's not listed under the vehicle, but it is listed as a bypass hose. You do have to cut to fit. I looked like the wrong hose initially, then you realize Toyota bent that hose to make it fit, so you're straightening it out instead of creating a tighter bend. Straightening a bent hose does not weaken it but creating a tighter bend certainly creates a stress point.

Most of the parts are available at the chain stores, so it's not that difficult. Just remember it's a 1MZ-FE at heart, so the parts are the same

So I replaced the hose today and figured I'd do all everything I can within reason. Ended up with new plugs (went E3, I've used them before and have had good success with them), rebuilt all injectors (go to PepBoys, they have a full kit to rebuild the injectors for about $8.00), cleaned out every single part with Berryman Parts cleaner or Carb/Choke cleaner in areas I couldn't/shouldn't hose off with water, and finally new gaskets everywhere. It was PITA but it was worth the $250.00 expense for all the parts.

I'll keep you guys posted if I get any mileage gains, since I was getting about 29mpg but hopefully I can get her up to 33mpg which is a cause for celebration with $4.00 So Cal gas prices.

A similar problem. Please help!
 

I've noticed steam intermittently coming out form under the hood of my car. A couple of data points:
1.) Paid the Lexus dealership to diagnose. They quoted $1,040 for repair. Said there was "a leak in the coolant valley." Their estimate also seems to imply that they will replace the thermostat and thermostat gasket as part of the repair. No mention of the bypass hose.
2.) Coolant levels remain stable. I haven't had to refill.
3.) Bypass hose doesn't look like it's leaking.
4.) No issue with overheating. Temperature remains stable.
5.) I've taken several endoscope pictures where the coolant is leaking. See attachments. Apologies in advance for somewhat confusing pictures. I the camera is right side up to the best of my knowledge.
https://cimg2.ibsrv.net/gimg/www.clu...c23b17929.jpeg
https://cimg8.ibsrv.net/gimg/www.clu...0806bc6ef8.png
https://cimg3.ibsrv.net/gimg/www.clu...593555a58d.png
https://cimg5.ibsrv.net/gimg/www.clu...f8df14ee39.png
https://cimg7.ibsrv.net/gimg/www.clu...9000f5581e.png
https://cimg8.ibsrv.net/gimg/www.clu...171a32f319.png
https://cimg0.ibsrv.net/gimg/www.clu...54bb7b8061.png
https://cimg1.ibsrv.net/gimg/www.clu...bf1bfc571f.png
https://cimg2.ibsrv.net/gimg/www.clu...042285c10f.png
https://cimg3.ibsrv.net/gimg/www.clu...5b0a611dbc.png
https://cimg4.ibsrv.net/gimg/www.clu...f4ab0f5779.png
https://cimg5.ibsrv.net/gimg/www.clu...8966b506bf.png
https://cimg6.ibsrv.net/gimg/www.clu...501b93f8e5.png
https://cimg7.ibsrv.net/gimg/www.clu...7748aa7520.png
https://cimg8.ibsrv.net/gimg/www.clu...7b3f748e4f.png
https://cimg9.ibsrv.net/gimg/www.clu...e6a57a3a03.png

I'd like to know what parts to order and if this is something that is out of my league to do. Also any recommended maintenance that I could easily do while I'm in there.

Any help or advice is greatly appreciated!

Looks like the intake manifold gaskets are leaking or the bypass hose, or both. Here's what you'll need to do the job

bypass hose 17177-20020 (don't use anything but genuine)
plenum gasket
intake gaskets
Toyota long life coolant or equivalent
distilled water

Also if needed a good time to do the rear valve cover gasket and replace the plugs.

I would also suggest changing your knock sensors and wiring harness. The harness becomes brittle and could break while working in the area. It would not be apparent until the job is completed and you go for a drive.

Thank you guys! I'm going to order the parts and take this on!