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Occasional Overheating

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Old 05-27-14, 12:49 PM   #1
groverwood
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Default Occasional Overheating

I have a '93 SC400. I bought it a few years ago for $2200 and have put bits of time and work into it here and there. replaced instrument panel, fuel pump mod, replaced radiator, O2 sensors, and a few other odds and ends Its a fun little toy car with ***** and i love driving it.

My current problem is with the thermostat, radiator, water pump. I'm looking for somebody to tell me it;s not totally screwed.
What happens is the car will run fine and all, but gets hot, real hot. The fan doesnt kick in, i don;t get hot air from the vents unless I race the engine and get the RPMs up.

once i get the engine rockin' the temp gauge comes down to mid level.

I've since replaced the thermostat and taht didn;t help so, i replaced the thermostat again with a better one. Still no help. I have attempted to burp the raidator and i think i got all teh air out, but still have the problem.

Somebody suggested it may be the water pump. Is it this? Is there any other thing it could be? How much of a pain is the replacement project?

Thanks for the advice,. This place rocks, great community.
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Old 05-28-14, 08:05 AM   #2
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it was 1 gallon low on coolant. I added water and drove for an hour with no overheats. I'm really hoping it's just air
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Old 05-29-14, 10:01 PM   #3
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If your fans are not coming on check the wires to them. Also check the fan clutch.
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Old 06-04-14, 10:57 AM   #4
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It's been stable for the last week+. I think it was air in the line and it finally cleared out.


Thanks
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Old 06-04-14, 11:45 AM   #5
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I have been around here long enough to know whenever someone with a sc400 says there is no heat, they are low on coolant (do a search and you will see). has happened many times in the past when the 1uz is even a little low on coolant you loose hot air from the vents and the low coolant and air will give you those overheating issues if its bad enough, but not everyone gets the overheating, sounds like yours was quite low. that should take care of it though, and if it comes back burp it again with the heater on full blast this time.
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Old 06-04-14, 12:06 PM   #6
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Thanks again.

any clue as to why, when it's running at normal operation, I don't get vent air. What i mean is, if I open the vents and try to get some air (not A/C air, just air) it comes out hot.? I replaced the climate control unit thing last year and that did not help. It just seems the car gets hot and has no other way to discharge that hot air other than the cabin vents
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Old 06-04-14, 03:03 PM   #7
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most likely the heater control valve has gone out, and that or someone bypassing it previously lets the coolant circulate through the heater core at all times, instead of when just the heat is on.
check to see what yours looks like and if the vacuum line connected to it is still good and connected.
do a search or start reading here
http://www.clublexus.com/forums/perf...rol-valve.html

you would want to fix it as it will make your a/c work double in the summer, cause of it having to fight the heating affect from the hot coolant as well.
the oem part is expensive (which is why some people remove it and bypass it altogether but its not a good idea long term or if you use the a/c), but you can get an aftermarket replacement there are several DIY's on the topic, check towards the end of the thread posted above I think there are part numbers on the last page or 2. the replacements are very reasonable compared to the OEM price, but takes a little patience to retrofit it.
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Old 06-12-14, 10:45 AM   #8
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Overheating started again. yesterday i had to pull off the side of the highway and wait for it to cool off so I could add another 1/2 gallon of water.
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Old 06-12-14, 12:33 PM   #9
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Sounds to me like you're losing coolant....Is it dripping out or burning?
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Old 06-13-14, 07:24 AM   #10
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I see no leaks/puddles so it must be burning.

where is it burning?

anybody wanna buy a Lexus?

Last edited by groverwood; 06-13-14 at 10:02 AM..
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Old 06-14-14, 03:37 AM   #11
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Did you check the valve like was suggested in post #7?

Or you never burped the system prperly. .

Does the car smoke?

Last edited by GSXMike; 06-14-14 at 03:41 AM..
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Old 06-16-14, 11:55 AM   #12
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I replaced that valve last year with a used on I bought from a CL member. I believe I burped the system. numerous times, probably. And there is no smoke. It's almost as if there is a leak, but I don't see any dripping or puddles or anything.

I'll take a closer look at that valve tonight, There's got to be something off somewhere. I don;t see how it can go through so much water/coolant and not have a leak or bad head gasket.
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Old 06-17-14, 07:20 AM   #13
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I would also highly recommend adding some uv dye to the cooling system.
just because you don't see any puddles doesn't mean there aren't any leaks
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Old 06-30-14, 07:16 AM   #14
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OK. so I did the HCV fix mentioned above:

http://www.clublexus.com/forums/perf...rol-valve.html


it was incredibly easy.

Filled up the radiator reservoir and, so far so good. It usually takes a couple days for the issue to present, so We'll see what happens this week.
Thanks.
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Old 07-11-14, 10:45 AM   #15
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Q: "any clue as to why, when it's running at normal operation, I don't get vent air. What i mean is, if I open the vents and try to get some air (not A/C air, just air) it comes out hot."

I'm pretty sure this is what I've got going on, too. My vacuum hoses are all new and look to be routed correctly. I did the continuity and ground tests on the heater control valve's VSV and they checked out okay, but I didn't do the blow-through (with and without battery power) test since the port configuration is different than the EGR and fuel pressure VSVs, so I wasn't sure what exactly to check.

Is there anything else I can test, or do I simply need to replace the heater control valve? I haven't measured my cold air relative to outside temps -- tough to know what to compare to since both will be warmer at a standstill than when moving -- but it's at least 10 degrees warmer. A/C is cool but not icy cold. Heat works just fine. Pretty much every other thread I've found deals with cold air but no heat.

Quote:
Originally Posted by Ali SC3 View Post
most likely the heater control valve has gone out, and that or someone bypassing it previously lets the coolant circulate through the heater core at all times, instead of when just the heat is on.
check to see what yours looks like and if the vacuum line connected to it is still good and connected.
do a search or start reading here
http://www.clublexus.com/forums/perf...rol-valve.html

you would want to fix it as it will make your a/c work double in the summer, cause of it having to fight the heating affect from the hot coolant as well.
the oem part is expensive (which is why some people remove it and bypass it altogether but its not a good idea long term or if you use the a/c), but you can get an aftermarket replacement there are several DIY's on the topic, check towards the end of the thread posted above I think there are part numbers on the last page or 2. the replacements are very reasonable compared to the OEM price, but takes a little patience to retrofit it.
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Old 07-11-14, 10:45 AM
 
 
 
 
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