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lexis lexus

Overheating

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94 es 300 w/ 111k, bought 1 month ago, overheated on the way home, but found cap to resevoir flopping free spewing coolant on the abs pump. Added 1.5 gal coolant, got a new rad cap and it was good to go. 300-400 mi later, overheated today, resevoir bubbling away. Took 3/4 gal of coolant, running ok now.

I'm thinking head gasket?

How common do these blow?

Any way to tell which head?

Lex

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The first thing I would check is the thermostat. You are bubbling out, not losing coolant through the combustion system. If coolant were dissappearring without flowing olut into the expansion tank then I would look at the head gasket. If you keep overheating, you may need a new head though.

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When does the overheating occur? Is it when the car is moving at speed, or when it is moving slowly or idling?

A very common problem with the 94 ES and the other mid-90's models involves the hydraulic cooling fan. The fan is operated by fluid from the power steering pump. When the temperature coolant sensor senses the need for more cooling from the fan, a signal is sent to the power steering pump. The pump increases the flow of fluid, and the fan speed increases. There is a wire harness which connects to the power steering pump. This harness must be connected for the cooling fan to operate properly. It seems that this harness often gets disconnected when work is done on the power steering pump and other engine components in this area. Since the hydraulic power steering fan is not seen on many cars, many folks doing mechanical work on these engines do not realize how important this connector is.

If the connector is not attached properly, the cooling system will probably work okay when the car is moving at speed where air flow is sufficient to keep the coolant temperature down. However, when the car is moving slowly or idling, proper fan speed is necessary to cool the engine.

Make sure this connector is plugged in.

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The first thing I would check is the thermostat. You are bubbling out, not losing coolant through the combustion system. If coolant were dissappearring without flowing olut into the expansion tank then I would look at the head gasket. If you keep overheating, you may need a new head though.

That makes sense. I have this service manual on pdf purchased on fleabay, (92-96 coverage, reads like a fsm, but...) showing tstat on front of engine on top of water pump. But on my 94, the tstat/inlet appear to be on the rear of the forward bank. Is there a pipe running to the water pump up front (Ive seen this in other cars)? Looks a bit tricky to get it out of there, expecially the bottom bolt (hands like a child needed I think....).

Anybody w/ some experience/tips about this?

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When does the overheating occur? Is it when the car is moving at speed, or when it is moving slowly or idling?

A very common problem with the 94 ES and the other mid-90's models involves the hydraulic cooling fan. The fan is operated by fluid from the power steering pump. When the temperature coolant sensor senses the need for more cooling from the fan, a signal is sent to the power steering pump. The pump increases the flow of fluid, and the fan speed increases. There is a wire harness which connects to the power steering pump. This harness must be connected for the cooling fan to operate properly. It seems that this harness often gets disconnected when work is done on the power steering pump and other engine components in this area. Since the hydraulic power steering fan is not seen on many cars, many folks doing mechanical work on these engines do not realize how important this connector is.

If the connector is not attached properly, the cooling system will probably work okay when the car is moving at speed where air flow is sufficient to keep the coolant temperature down. However, when the car is moving slowly or idling, proper fan speed is necessary to cool the engine.

Make sure this connector is plugged in.

CU,

The first time it overheated, as I noted was the day I bought it, driving home, surface streets, about 15 miles. The resevoir cap was not on/in and overflow was not being saved (I missed that on inspection of the vehicle, and it didn't overheat on test run of 15 minutes). I filled w/ coolant 1-2 gals(when it had cooled down) so it was pretty empty. The 2nd and last time it overheated was about 2 tankful's later (400-500 mi, 3 weeks). I hadn't been checking coolant as I thought I'd solved the problem by replacing resevoir cap. My suspicion was that I was losing coolant slowly. No obvious leaks.

I did check the connector at the power steering pump, and it was intact; noted fan running nicely as well (is that a weird setup, seems to me a variable speed electric motor would have less problems, take less parts, etc). Burped the system, taking it up to 190 degrees, just a few bubbles noted nothing big, but nice of them to put the rad cap up so high...

My plan is to run it for a while, checking coolant regularly to see rate of coolant loss, use cardboard under car to ck for leaks and await some imput on how to to the tstat which contrary to the fsm I'm using, is located behind the front bank, and I can't seem to find a water pump on the front at all? Where is it? If/when I replace tstat, if it keeps loosing, may consider some cooling system stop leak to target a gasket....

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The water pump is behind the timing belt cover, the thermostat plugs into it.

DJ

That's the same pix I have, but not what is actually under the hood. The return hose from radiator comes off the bottom right (facing toward firewall), runs into a silvery tube that connects to a t-stat like housing that's attached to the block just below the right front tip of the intake manifold. I saw a similar one in the upullit today, think it's a 94 like mine, but the 92 I looked at had the tstat housing as in your picture.

Anyone have experience w/ a set up like mine?

Lexis

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The water pump is behind the timing belt cover, the thermostat plugs into it.

DJ

That's the same pix I have, but not what is actually under the hood. The return hose from radiator comes off the bottom right (facing toward firewall), runs into a silvery tube that connects to a t-stat like housing that's attached to the block just below the right front tip of the intake manifold. I saw a similar one in the upullit today, think it's a 94 like mine, but the 92 I looked at had the tstat housing as in your picture.

Anyone have experience w/ a set up like mine?

Lexis

I looked over at rockauto to see what kind of water pumps they have for your car and all of them are timing belt driven. Even if yours isn't, it would still need a belt attached to it to make it work. I've attached a pic of my pump. To get to it there is a metal plate you have to take off after you open up the timing belt cover. The pump is that shiny thing at the top, the coppery colored tube at the bottom is the crankshaft. The camshaft pulleys would be above & to either side of the pump. Just looked through a book I have and maybe your setup looks like picture #2?

DJSG3

post-62551-128201304884_thumb.jpg

post-62551-128201453994_thumb.jpg

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The water pump is behind the timing belt cover, the thermostat plugs into it.

DJ

That's the same pix I have, but not what is actually under the hood. The return hose from radiator comes off the bottom right (facing toward firewall), runs into a silvery tube that connects to a t-stat like housing that's attached to the block just below the right front tip of the intake manifold. I saw a similar one in the upullit today, think it's a 94 like mine, but the 92 I looked at had the tstat housing as in your picture.

Anyone have experience w/ a set up like mine?

Lexis

I looked over at rockauto to see what kind of water pumps they have for your car and all of them are timing belt driven. Even if yours isn't, it would still need a belt attached to it to make it work. I've attached a pic of my pump. To get to it there is a metal plate you have to take off after you open up the timing belt cover. The pump is that shiny thing at the top, the coppery colored tube at the bottom is the crankshaft. The camshaft pulleys would be above & to either side of the pump. Just looked through a book I have and maybe your setup looks like picture #2?

DJSG3

DJ,

Ya, #2 is looking a lot like my set up, particularly at the back of the engine w/ the heater hoses. I have a similar water fixture there, I assumed is the inlet, but is outlet in pix. However, what would then be the inlet, usually next to the water pump seen in your pix, is in front but at the top most part, w/ the rad cap, not down low as in the pix. I'm sure your right about the water pump being up front, as it typically is (timing) belt driven. I can't see it as it's hidden behind the timing belt/cover. Now where is the darn t-stat!

Lexis

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