Es250 Overheating, New Radiator

[bjd]

Hi,

I have a 91 ES250 that has been overheating. The radiator is new; the hoses are transferring water, although sometimes the heater does not get warm.

The water pump does not leak any coolant from the weep holes (assuming it has weep holes), so I assume it is working properly, but I could be wrong. Water does move through the engine because it gets to the top hose and circulates.

It seems as though their may be some ciculation problem due to the heater issue. I bypassed the heater it in case the core was clogged up; however, the overheating issue remained.

Should there be a certain pressure or volume of water that the water pump should be moving? And if so how do you check it?

The thermostat is good.

I don't want to replace the water pump if it is not broken. That would be a big waste of time because it is tough to work in the confined area.

Is there some tried and true way of testng your water pump and circulation without pulling things out first?

Anybody?

Bill :(

[monarch]

Was a genuine Toyota thermostat and thermostat gasket installed? Do the electric cooling fans come on when the temperature gauge gets about 1/2 the way up the dial? Under what driving conditions does it overheat? Is the coolant a mixture 50% antifreeze and 50% water?

[bjd]

Was a genuine Toyota thermostat and thermostat gasket installed?  Do the electric cooling fans come on when the temperature gauge gets about 1/2 the way up the dial?  Under what driving conditions does it overheat?  Is the coolant a mixture 50% antifreeze and 50% water?

←

Wow, thanks for the fast response.

Yes, the thermostat is genuine Toyota. Fans come on when they should. 50/50 mixure.

Driving conditions:

Pretty much after about 10-15 min of driving normally, with or without putting on ac.

The car is also running a bit rough at idle. I adjusted the timing a little to smooth it out as best I could and turned the idle up to about 1000rpm in neutral. This is sort of a quick fix. It has new plugs and wires and the cap and rotor are only a year old. So I don't think ignition is a problem. I wondering if the rough idle and cooling problem are related.

I first started to notice the cooling problem after a long trip from Houston to Phoenix and back. I'm wondering if something is causing blockage somewhere. I backflushed the cooling system, but that didn't help either.

Bill

[Toysrme]

Recheck the thermostat, check that the pump is pumping, check for blockage, check pressure cap<s>.

The pumps don't leak unless their gasket is damaged.

If you don't stay on top of coolant changes, it's pretty common for water pump impellers to corrode away (regardless of make).

My guess is that barring the thermostat is faulty / installed incorrectly, the pump may be damaged.

A side note

Stop playing with the adjustments until you fix it. Put the car in Diagnostic mode & set the timing @ 10*btdc. You can overheat an engine by incorrect ignition timing fairly easily without pinging. We can all flash back to the time I advanced my distributor till it sounded good & later found out after it started running like !Removed! that it was 40*btdc base timing LoL!

& don't play with the air-flow meter bypass, the throttle body screw, or the coolant sensor either. The ECU sets it's own idle speed. It'll run whatever it should be running.

[bjd]

Recheck the thermostat, check that the pump is pumping, check for blockage, check pressure cap<s>.

The pumps don't leak unless their gasket is damaged.

If you don't stay on top of coolant changes, it's pretty common for water pump impellers to corrode away (regardless of make).

My guess is that barring the thermostat is faulty / installed incorrectly, the pump may be damaged.

A side note

Stop playing with the adjustments until you fix it. Put the car in Diagnostic mode & set the timing @ 10*btdc. You can overheat an engine by incorrect ignition timing fairly easily without pinging. We can all flash back to the time I advanced my distributor till it sounded good & later found out after it started running like !Removed! that it was 40*btdc base timing LoL!

& don't play with the air-flow meter bypass, the throttle body screw, or the coolant sensor either. The ECU sets it's own idle speed. It'll run whatever it should be running.

←

Yeah, I'm starting to lean towards pulling out the water pump, although I hate pulling transverse V6 pumps. I sure love my old 78 Chevy Van that has a fan belt to loosen and 4 bolts and lots of space.

The whole ciculation problem seems to have happened gradually, so maybe the impeller was decaying and finally reached the point where is was still circulating water, but not enough to cool down the car. The comment about the pump not having weep holes and leaking is helpful because that was what was hanging me up from changing out the pump. That and the fact that there is some water circulating but doesn't appear to be of high volume.

[bjd]

One thought I just had,

If I pulled out the thermostat completely first, and still encountered overheating, shouldn't that confirm that my water pump just doesn't have any muscle left?

If the cooling problem vanished, then I could blame the new thermostat as faulty and just get another one.

Any comments on this idea? Or will the computer freak out from the temperature sensor due to the lack of temperature control that the thermostat provides.

Will dogs and cats be sleeping together after that?

I have a bunch of vehicles. Some call me a collector, others call me crazy.

Two vehicles are Y2K compliant, ie, no onboard computers. These types of ideas I come up with work great on those vehicles.

[steviej]

before you go through all this, have you eliminated the radiator caps as suspect?

steviej

[Toysrme]

Werd. The only thing better than $5 fixes are sub $5 fixes LoL!

Ya you can run without a thermostat.

Werd on changing timing belts / water pumps on this type of stuff. Remember it could be worse. on the 3.0+ you have enough room for a wratchet to take the bolts partway off, then finish by hand! :(

[bjd]

Yes, the radiator cap is new also. I should have mentioned that.

Thanks for all the comments so far. I think I'm going to try thermostatless and try that idea.

Bjd

[monarch]

The thermostat gasket on Toyotas typically fits on the thermostat itself; therefore you may not be able to seal the thermostat housing to the engine if you remove the thermostat.

If I owned your car I'd be concerned about the rough idle. I'd want to get the engine's compression tested to make you don't have low compression on one or more cylinders due to a leaking head gasket, mechanical engine damage or excessively tight valve clearances, all of which would tend to contribute to the engine's tendency to overheat. If the compression tests out good (high and even on all cylinders) and you have verified the spark plugs and ignition timing are good and that the catalytic converter isn't clogged, then I'd look more closely into restricted coolant circulation .

Another idea: Idle the engine for 10-15 minutes with the radiator cap off and watch the temperature gauge. If the temperature gauge rises way above the 1/2 point on the temp gauge dial, but the coolant doesn't begin to boil over then your actual coolant temp is normal (180 degrees) and the temp gauge is faulty.

[bjd]

You know Monarch,

That sounds like really good advice. It seems like the rough idle and the cooling probem developed together, although I'm not completely sure.

A compression test is not a bad idea, although that means I have to get to those friggin' rear plugs again. Crap. I guess you can do a compression test with the throttle body assembly off, right? I'm just compressing cylinders and the throttle body doesn't tie into that compression in any way, right? I suppose that would be the same as doing a compression test with a carbeurator removed. As you probably are realizing I have not ever done a compression test on a fuel injected car, just detroit iron V8's with carbs.

[yes250]

Well, I finally got around to replacing that water pump. Turns out the bozo that replaced the timing belt before me had the cam #1 BTDC marks about 90degrees off from the camshaft sprocket #1 BTDC mark.

I put in the water pump, repositioned the cams and crakshaft correctly. Now the car runs beautifully and remains cool.

When reassembled, I also had to backflush the crap out of the car. That seems to be a better way to purge air from the system also.

230,000 miles and running great again, my 91 es250.

PS I'm bjd. Now wjdthree.

Well, I finally got around to replacing that water pump. Turns out the bozo that replaced the timing belt before me had the cam #1 BTDC marks about 90degrees off from the camshaft sprocket #1 BTDC mark.

I put in the water pump, repositioned the cams and crakshaft correctly. Now the car runs beautifully and remains cool.

When reassembled, I also had to backflush the crap out of the car. That seems to be a better way to purge air from the system also.

230,000 miles and running great again, my 91 es250.

PS I was bjd. Now I'm yes250.

[Toysrme]

Awsome job!

Ya... Cam alignment newbies. It's sad too, cause all of these v6 engines are the flat easiest cams to align for the most part.

I'm glad you purged air out of it. I know a lot of people that forget to do that & wind up wondering why they keep overheating when they've got all new parts & good compression. :whistles:

[chargerucd]

Question,

how would one "purge" the system to remove air inside? i've wondered about that for a while.

you guys a re a grat help.

thanks,

[yes250]

Well, the Haynes and Lexus shop manual specify a procedure using a small air purge bolt with a hole in it up near the throttle body where the discharge hose meets up. However, I didn't have too much luck with that procedure.

What I did was put in 2 new hoses in between the radiator core and the engine and then in between the hoses, a t-fitting for a back flush system. Then I disconnected the engine input (bottom fat hose) hose from the radiator. I hooked up a garden hose to the t-fitting, warmed up the car so the thermostat would be open, and then opened the water valve on my house and blasted water through. Oh the crap that came out of the engine input hose! Once the crap was all clear, I hooked up the input hose and continued to backflush out the radiator. This is an important step because you don't want to clog up your radiator and heater core with crap from the engine initially. There could be big clogging chunks of corrosion and other goodies. In hindsight, it may be even wiser to remove the thermostat for the first step (in case of REALLY BIG chunks, and then reinstalll it for the radiator clearing step. However, the current method worked fine for me.

After the radiator was cleaned out, I drained some water out from the drain plug, and topped off with antifreeze, recapped, and filled the overflow reservoir with antifreeze. Abracadabra, all arteries were clear!