TriniTT

So I have a 93 s13 coupe with 216k miles, all stock engine components. It's a 5-speed. I was having overheating issues, so I replaced the thermostat with one from Autozone. Didn't fix my problem, so I decided my head gasket was probably blown after seeing coolant trickling from around the front side of the head.

I pulled the head, replaced the head gasket (the old one looked fine, no tears or anything) and valve stem seals (which needed replacing). I checked out the head and block for any wear and didn't see anything unusual, no visible warpage. Compression test verifies 150-158 across all cylinders. I also noticed that the coolant leak I initially saw was coming from below the water neck, and not the head, so I pulled it and redid the gasket for it. It's now no longer leaking.

I also replaced the thermostat with an OEM Nissan one, along with a new water pump (again, old pump looked fine), and a new aluminum radiator with electric fans. I thought maybe the fans were part of the problem, so I put the oem fan+clutch back in, along with the e-fans.

Even after all this, it's still overheating. If I drive it about 3-5 miles, it begins to overheat. If it's sitting still at idle, it won't overheat unless I have already driven it and it has begun to overheat. I even plugged up my Consult to verify the ecu coolant temp sensor was getting the same reading that the gauge cluster was putting out, and it is. I have no coolant leaks coming from anywhere. I'm out of ideas here. Any suggestions are greatly appreciated.

Thanks.

Jonnie B

Sileighty_85

did you have the head machined flat before reinstalling?

95% of the time when you pull a head (even per FSM) the head will be warped, and needs to be machined.

you will not be able to tell by looking at it. You need to use a straight edge and feeler gauges to determin the warpage if you choose not to take it to a shop.


Also are you sure you bleed all the air out? KA's are notrious for holding air pockets

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後輪駆動車１番
1989 Built SR GT2871R -363whp
1998 S14 W/RB25- 250ish (For Now)
1986 SR86 - 200ish
1990 R32 GTR - 320hp
Don't Buy Engines from JDM-Online http://zilvia.net/f/businesses/207457-jdm-online.html
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Killa_D

did you replace your temp sensor also did you bleed the system correctly and please put your clutch fan and fan shroud back on.

STEEZxIT

x2.

Since i wanted to be cool and put E-fan on stock motor and rad, shit went to hell, car runs warmer than normal. Operating but not like with the OE fans.

And yeah bleeding the system precisely is the key. An air bubble next to the thermostat wont make it operate correctly.

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@dangerdamian

TriniTT

Like I said in my initial post, I'm running the stock fan and clutch, along with a set of altima electric fans. The fans are not the issue; there is more than enough cooling capacity. These engines run cool to begin with (this is my 9th 240sx, and I work on them regularly, so I'm not exactly new to these cars).

I did not have the head remachined when I had it out, but I doubt that's the issue because I was having the same exact problem before I pulled the head off.

I'm sure I bled the system correctly, as again I've done it a million times. I'm not running low on coolant either. I didn't replace the temp sensor(s), didn't see a need to because both the gauge temp sensor and the ecu temp sensor are showing the same readouts. It would be a cosmic coincidence for them to both be giving a false readout.

Thanks for the suggestions. Any other ideas?

Sileighty_85

So how do you know the head is not the issue?

If the head warped at a coolant passage then it will send combustion gases into the coolant system causing it to over heat. (Seen it happen a few times)

Also might wanna check out the RAD cap for shits and giggles

__________________
後輪駆動車１番
1989 Built SR GT2871R -363whp
1998 S14 W/RB25- 250ish (For Now)
1986 SR86 - 200ish
1990 R32 GTR - 320hp
Don't Buy Engines from JDM-Online http://zilvia.net/f/businesses/207457-jdm-online.html
Don't Buy XS-Power or SSAC Shit

TriniTT

I don't know it isn't the issue, I just said I doubt it is. Really, my inclination was leaning towards warpage there, I just wanted to get feedback to see if anyone had any other ideas. I figured I would have at least seen some sort of indicator from the old head gasket that the head was warped from before I pulled it, but I suppose I wouldn't necessarily.

Also, if the rad cap was the culprit, I'd be losing coolant and I'm not. Still have an overflow reservoir and it's not bubbling over or even coming close.

STEEZxIT

^^ yes rad cap was my issue after changing thermostat water pump, hoses and such.

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@dangerdamian

STEEZxIT

Did you check your fluid on the reservoir if its even warm.

Doesnt have to bubble up, because rad cap isnt holding pressure so it jst lets the fluid to fill the reservoir.

anyways.

check to see if your heater is working maybe its jst bleeding issues. Bleeding the motor is quite a headache at times. Especially if its your first time, which im sure it aint since you've had 9. You can always bleed it again.

And maybe test each cylinder for compression just to check if the head is warped.

other than that, thats all i can think of.

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@dangerdamian

TriniTT

Something STEEZxIT said got me thinking, so I went and bled the hell out of the system again, for probably the 5th time. While I was bleeding it, a huge air bubble popped out of the bleeder screw hole, and I think that got it. Drove it around for a while and the temp held steady.

When he said "check to see if your heater is working", that had me scratching my head bc the heater wasn't blowing super hot like the other 240s I've owned. Thought maybe it was just bc it was a different car, and I haven't owned it long enough to have ever used the heater. But when I put that along with the overheating issue, I got to thinking there was probably still air in the heater lines.

Turns out I haven't seen everything

Thanks a lot for the input everyone, at least it got me to check everything to make sure I'm on top of my game.

STEEZxIT

good shit man... glad i can help.

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@dangerdamian

marcojdm

when i put an aluminum radiator in my ka it would overheat no matter what i did. i took the thermostat out and now no more issues at all. good luck

ShimiBoi

maybe u had an air bubble too. driving without the thermostat sounds kinda risky and shady. but hey...to each his own.

romero87

driving without a thermostat isn't really risky... but you lose your heat for the most part or until you have the car running under a load for a long time... but with no thermostat it can cause your mpg to drop due to a lower engine temperature.... air bubbles are leading cause to most overheating problem....

nismoman

Running without a thermostat can keep the ecu from switching to open loop and closed loop it it never reaches the temp it's looking for. Won't run properly.

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ShimiBoi

lets jus put it this way...it isnt recommended to run without the thermostat because it wont run as efficiently as normal. however, its possible...but most people wouldnt suggest it.

boosted KA24DE

If your radiator is partially clogged it will over heat as you begin to drive. It will stay cool at idle because there is very little load in pressure going through the radiator. Once you get on the highway and put more loaded pressure through the radiator it will begin to bottleneck and cause your overheating issue. I do not recommend not having your termostat out. I have gone through the extent of cutting open a rad to show a buddy how clogged actually was.