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91 VR4 wish scissors BBK wheels and tint
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Discussion Starter #1
Hey again...
VR4 91, 230k stock boost, at writing the driveline was 100% stock, except a cone air filter)

After the last thread I burped the system and topped it off with 50/50 mix.

So last night (only 55F) I took the out again, got gas a few blocks from my house, turned the heater OFF, got on the freeway went about 30ish miles ands it over heated... pulled over, tons of steam. When it had cooled enough I topped off the coolant and went straight home, on the same route.

This time I turned the heater on FULL BLAST, with fresh air (not recirculating)
After a very warm trip I made it back home the same distance, not overheating... coolant is at the same level it was when I overheated/topped it off. (though I did not spent the time to burp it on the side of the freeway)

So now I am stuck... I was driving on the freeway doing 70-80mph the whole time... but with the heater on it did NOT overheat.
Knowing that Ive replaced most of the cooling system Im lost on as to WHY its overheating.
I suspect the radiator is not getting hot fluid, but Ive replaced the thermostat... and I did test the old one, while it was a bit crusty, and "ticked" open vs opening smooth... it did open up just before the pot boiled.

this is an update to this thread:

again to recap:
new radiator (flushed when doing the below)
new thermostat (170F)
new radiator cap
new radiator hoses
mixed 50/50
 

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I can't really remember from the last thread but we are sure your water pump and fans are working correctly? 1g cars actually have 3 temperature sensors for some damn reason. Two in the radiator(one for the radiator fan, one for the AC) and on in the thermostat housing(ECU reported temperature). At idle the fans should kick on around 200(203 maybe?) And kick on high around 209 I think.

Is the thermostat in upside down? The little flappy relief port should be at the 12 o'clock position.
 

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I mentioned thermoswitches in the previous thread as opposed to ECU controlled...

291274


291275


-sent from my Galaxy Note 9
 

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I mentioned thermoswitches in the previous thread as opposed to ECU controlled...

View attachment 291274

View attachment 291275

-sent from my Galaxy Note 9

I knew the fans turned off at speed, just figured it would be higher than 50mph. That actually explains a lot, even for my car with a FMIC and new water pump/radiator. Guess I need to make some ducting(it also doesn't help that the 3sx radiator fan mounts leave quite a gap)!

Also it's hard to tell based on what you posted, but does that mean the ECU and thermo switches are basically redundant? As in the fans will turn on by the switches at the designated temperature regardless of the ECU, and the ECU will turn on the fans regardless of the switches?
 

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91 VR4 wish scissors BBK wheels and tint
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Discussion Starter #5
I can't really remember from the last thread but we are sure your water pump and fans are working correctly? 1g cars actually have 3 temperature sensors for some damn reason. Two in the radiator(one for the radiator fan, one for the AC) and on in the thermostat housing(ECU reported temperature). At idle the fans should kick on around 200(203 maybe?) And kick on high around 209 I think.

Is the thermostat in upside down? The little flappy relief port should be at the 12 o'clock position.
I haven't removed the water pump yet (I will do it when I do the timing set)
However, there does seem to be good flow, when I did the thermostat there was very minor deposits on the housing (both sides) and with the cap open there is a nice swirl at idle, if I rev slightly it flows accordingly.

The previous owner wired the fans to a medium or lower setting when key is on... but the overheating when Im doing 70+ on the freeway indicates to ne airflow isnt the problem (and I still have stock intercoolers)

I did replace the ECU sensor.
the dash sensor is reading as it should
the fan sensor, well its hardwired ON so im not concerned...
I think there is a 4th for the AC too... not related to my current thread.
 

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91 VR4 wish scissors BBK wheels and tint
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Discussion Starter #6
I mentioned thermoswitches in the previous thread as opposed to ECU controlled...

-sent from my Galaxy Note 9
good info for when I'm fixing my AC...

I don't see how that applies to my car belching out steam when I was doing 70+ mph in 50 degree weather.
The radiator and thermostat are not ECU anything.
 

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Your logic is ass backwards...

Good airflow usually means that the engine will run at an appropriate temperature with the fans off while at speed - not the case here.

Ambient temp does not matter if things are not functioning correctly. Undo the fan f*ckery and report back.

-sent from my Galaxy Note 9
 

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91 VR4 wish scissors BBK wheels and tint
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Discussion Starter #8
Your logic is ass backwards...

Good airflow usually means that the engine will run at an appropriate temperature with the fans off while at speed - not the case here.

Ambient temp does not matter if things are not functioning correctly. Undo the fan f*ckery and report back.

-sent from my Galaxy Note 9
I agree with fixing the fans, but perhaps I'm missing something then...
How do you think the fans would make a difference (assume I fix the wiring)

It would seem to me that doing 70 mph would provide more than enough fresh air to keep the engine cool for cruising in 5th at 70.

I'll fix the wiring this weekend and report back...
 

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91 VR4 wish scissors BBK wheels and tint
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Discussion Starter #9
Actually, speaking with a friend... I guess the "catfish camero" has a lower air scoop under the faux grill that keeps it from overheating.
Anything like that on the VR4?
I know I'm missing the front active aero and engine cover behind my front driver side wheel.

is there something I should look for specifically?
 

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Actually, speaking with a friend... I guess the "catfish camero" has a lower air scoop under the faux grill that keeps it from overheating.
Anything like that on the VR4?
I know I'm missing the front active aero and engine cover behind my front driver side wheel.

is there something I should look for specifically?
Yes there should be ducting that sounds like what you described. There should be ducting basically all around, between the front bumper opening and the radiator. If you have any gaps between the front bumper opening and the radiator where air can go around the radiator instead of being forced through it, the vast majority of the air is going to take that path of least resistance. I dont have a OEM front bumper but i still have the plastic that goes from radiator to under the front bumper opening, so air is forced through the condenser and radiator.

Also, does the car overheat while idling for extended periods of time?
 

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Yes there should be ducting that sounds like what you described. There should be ducting basically all around, between the front bumper opening and the radiator. If you have any gaps between the front bumper opening and the radiator where air can go around the radiator instead of being forced through it, the vast majority of the air is going to take that path of least resistance. I dont have a OEM front bumper but i still have the plastic that goes from radiator to under the front bumper opening, so air is forced through the condenser and radiator.

Also, does the car overheat while idling for extended periods of time?
It looks like I have something on the lower, I dont know if thats correct for the top?

Ive never tried letting it idle for an extended period of time.
 

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Yea the ducting is there. But your condenser is SUPER dirty. If your condenser is clogged up, air can't get to your radiator. Go to Walmart/Lowes/Home Depot and get some condenser cleaner in a can, spray it on and then use a soft bristled brush to agitate the dirt, then rinse it off. I'd go from the backside of your radiator too to ensure whatever you blast out of the condenser doesn't get logged in the radiator too.
 

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Yeah ducting looks like its there. Make sure its 'airtight' the best it can be to force air through radiator. Also +1 for cleaning everything.

As far as the idling goes, if you are able to let the car idle for an extended period of time on a warm day without it overhearing, that would be evidence that your fans are working properly.
 

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I had a cooling issue with my previous VR4 that I was hunting down for a while. The high temp/fan speed sensor was shot in the bottom of the radiator.

One fan would always click on when car warmed up and the other would turn on when the AC was turned on to low speed. With the AC on and its fan going it’d control the temp but under heavy load it’d start over heating.

The high temp sensor when it trips activated the AC fan in high speed and does the heavy cooling.

I removed the strut blister on hood to help with air flow escaping to back of engine bay to make it home. It worked a bit bit not entirely.

Sensor is very easy to replace and a cheap part.
 

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But if your blowing steam it means your system isn’t pressurizing and coolant is boiling and escaping through something.

Hunt down where the steam is coming from and that is most likely where your pressure is escaping.

Being under pressure it raises the boiling point of the water.

Temp gauge will creep up because air/steam will be messing with the sensor at the fill neck and looking hotter then it really is.
 

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Feel the lower radiator hose when it’s at operating temperature to feel for warmness.

If it’s COLD like ambient temperature your radiator could be clogged up.
 

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91 VR4 wish scissors BBK wheels and tint
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Discussion Starter #17
I had a cooling issue with my previous VR4 that I was hunting down for a while. The high temp/fan speed sensor was shot in the bottom of the radiator.
Sensor is very easy to replace and a cheap part.
I'll test that sensor and or replace it.

But if your blowing steam it means your system isn’t pressurizing and coolant is boiling and escaping through something.
Hunt down where the steam is coming from and that is most likely where your pressure is escaping
Being under pressure it raises the boiling point of the water.
Temp gauge will creep up because air/steam will be messing with the sensor at the fill neck and looking hotter then it really is.
You miss understand... I am holding pressure, its getting THAT HOT.
It's getting so hot that its pushing the rad cap open (a new one) and venting out through the overflow.... and then the overflow is coughing up coolant too
The water pump IS pumping, I need to check if the radiator hoses are getting hot.
for sure the heater core is getting coolant (only way I can drive it) but I dont think its flowing to the primary radiator.

Feel the lower radiator hose when it’s at operating temperature to feel for warmness.

If it’s COLD like ambient temperature your radiator could be clogged up.
when I swapped my radiator hoses I put my garden hose in the upper hose for 5 minutes to flush out whatever may have been building up.
for sure it flowed, this week I'll pull the radiator hoses again and put my borescope in the radiator/down the thermostat housing.
 

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You've got all the symptoms of a leaking headgasket. . The easiest cheapest fix is to retorque the heads before it gets worse. If you catch it early, then retorquing always works but if you let it get worse, it won't work. The headbolts lose clamping load over time due to the softness of the heads.
 
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