Thoughts on overheating

[Cpt_Impossible]

Since I had my swap done in July I have been struggling with an overheating on my 90 240sx with RB20. It only happens on the freeway even off the boost. I have tried a lot of things to get rid of the problem and it has helped, but it still strays a bit hot on the freeway just cruising. If I stop and idle or just drive city streets it goes back down though. It isnt just a bad temp gauge though, the cap sometimes opens and the coolant resivoir level raises. Here is what I did in order.

Two 12" PushersUpper radiator Cooling PanelWater WetterFMIC (thought the smic was soaking too fast which it was)Lower Cooling PanelKoyo RadiatorNew ThermostatHonda OEM Coolant + Water Wetter

So like I said the problem is slight now, but I don't like flirting with disaster on my daily driver (which this hasn't been till I get it fixed). Today I took it to a good shop and told them to flush the block because I head read on skylinesaustralia that some of them had had freeway cooling problems because of a stuffed coolant passage in the engine. The shop has a nissan specialist who works mostly on racing motors and he told me not to bother doing the flush that it wasn't my problem. He ran a bunch of tests and told me that everything in the system is fine, headgasket is holding pressure, pump is flowing properly, radiator is good... He said that my problem is that with the FMIC in place the koyo isnt getting enough airflow, that the cooling fans didnt have enough air to blow. He advised that I should cut out the vents on my pignose or find a way to duct air directly to the radiator.

The thing that bothers me is that I had the same problem with my SMIC which was not in front of the radiator but at that time I was using the stock RB20 radiator which wasnt in the best shape at the time. A lot of bent fins and age.

Any thoughts from fellow pignose owners on whether opening up the vents would make that big of a difference or if there is something that I am looking over?

[themadscientist]

20s run hot as ****, that doesn't help. You would likely not have this problem with a 25. I can tell just by pulling my hand on an R32 which motor it has, it's that bad. A trick I have use is to washer up the back of the hood at the hinges so the engine bay can vent out across the entire back end of the hood. It's drastic though and if the look bothers you not a viable solution.

[dsm]

Take those fans off and see if it still overheats on the freeway. Try to fit a good puller or find some pushers that don't block that much of the rad.

[Cpt_Impossible]

Take those fans off and see if it still overheats on the freeway. Try to fit a good puller or find some pushers that don't block that much of the rad.

Pullers are out of the question, Koyo radiator leaves like 1.5 inches of space between it and the crank.

[Kansei240sx]

20s run hot as ****, that doesn't help. You would likely not have this problem with a 25. I can tell just by pulling my hand on an R32 which motor it has, it's that bad. A trick I have use is to washer up the back of the hood at the hinges so the engine bay can vent out across the entire back end of the hood. It's drastic though and if the look bothers you not a viable solution.

lol, thats awesome, i took washers and lifted my hood as well a few years back its seemed to work and i like the way it looks.

If you're sick an tired like i was... You'll ditch your koyo alum 3 row cut your radiator support up and put in FAL 220's and a copper SR20DET koyo and it will fit.... like so...



That radiator support will be re-attached, cut a bit more, and re-assembled to utilize a little bit more support and the stock hood latch.

[l0nestar]

You sir, rock!

Thanks for the info! (which I will be copying as well ) What hoses are you using for the SR20 radiator? Same ones as before? Thanks.

[Cpt_Impossible]

So I took off the bumper and cut out the fake vents. I am going to paint the exposed yellow plastic but it started raining (Seattle, go figure) so I will have to finish another day. I am planning on painting anything past the bodyline primer black so that it looks like a shadow.

[Carl H]

first off, what kind of gauge temp sensor is in the motor and second do you have a proper coolant temp gauge?if you are running the rb's temp sensor then its gonna read VERY strange, you should be using the ka temp sensor...

[Cpt_Impossible]

I am using the RB20 sensors. I have a cyberdyne digital temp gauge but with the koyo there was no room to install the sensor so it isnt doing me any good right now. It isnt just that it is reading hot. It is getting hot. It has boiled over in the past and after long freeway drives the coolant resivoir level is higher than when I left home and you can hear the coolant surging in the lines.

[DriftingisLame]

I had trouble bleeding my coolant system in the past and caused all kinds of over heating problems... I'm sure you've tried that, but just a suggestion.

I've heard pullers cool significantly better, especially on the highway because it does not affect the airflow. I'll be doing this when I get around to it.

[themadscientist]

That's a good point. If you had air trapped in the system it would hurt performance. Have you bled the system at the manifold? The highest point of the system is the bleeder screw on the front of the intake not the radiator cap.

[rotorimp]

My last 240 had that same problem--I fixed it by closing up the area on the sides of the intercooler,condenser and radiator. It was a huge difference. the air had no choice but to go through all three. Even at stoplights here in the AZ summer it was----->cool

[DriftingisLame]

Now I make sure to bleed the **** out of the system, squeeze all your heater hoses, lower and upper radiator hose, and pull the bleeder screw off of the manifold. I even pour a little water in the bleeder untill it spills out the filler on the radiator lol.. I bleed the system religiously.. Me and my roommates RB20's overheated like mad in Oregon heat, after my master bleeding teqniques were applied, I made it all the way to AZ and its held up in the heat.... so far, lol.

[Cpt_Impossible]

System was bled thoroughly every time the coolant was changed. I filled, bled with screw, ran, bled with screw, ran, bled with screw, ran, bled with screw, ran, bled with screw,... and then jacked up the car and ran while bleeding, then filled in the bleeder hole, then ran some more and bled again.

If there is air in the system car overheats like crazy, when the car is bled thoroughly its only overheating on the freeway a little but a little overheating is a little too much because it means I can't boost and sometimes have to pull off the freeway.

Right now the bumper holes are cut, and the paint is done, just waiting to dry.

[Kansei240sx]

I bet the coolant jackets in your block are clogged my friend....

My friends RB20 had the same problem yours did. When we went to replace the head gasket with a Trust HG it had goosh and solid orange **** in the coolant jackets in the block and the bottom of the head. That would be my last resort.

[alex288]

That could make sense.. My roommate back in oregon had the orangest coolant ever. We must have flushed it 20 times and used that intense coolant system cleaner in it... I mean, these are iron block engines, where do they come from? Probably sitting in a junkyard for a couple years full of fluids... RUSTING.

Perhaps try flushing it and then adding that coolant system cleaner, drive it a few miles, and flush it again...

I'm all out of idea's, your car shouldnt over heat, the last possibility I can think of is internal.

BTW this is driftingislame, on my roommates computer, lol

[Cpt_Impossible]

This is what I had read about on the skylinesaustralia forums. The shop I went to said that my coolant was flowing fine though and flushing was a waste of money.

My coolant isnt orange at all, its blue. In an effort to cool the engine better I now use honda OEM coolant, the good stuff. Car has been driven maybe 150 miles since the change to blue and coolant still looks new.

[DriftingisLame]

I'm not talking about the kind of coolant you use or how often you flush it, I was just sayin you might try that coolant system cleaner that you're supposed to run for a few hours or so and then flush out... a bunch of crap should come out if it really needed it.

[Jesse J]

I would check your AF ratios if possible, you could be running too lean under low throttle loads. Extended periods of lean A/F's lead to increased EGTs and increased coolant/oil temps. Also, I wouldn't trust the shops flow test seeing as how there is no way to tell whether a quintessential peripheral coolant channel is plugged. Also, replace all those rubber hoses and metal coolant line gaskets underneath your intake manifold. Just some ideas I had. I too had many problems with my rb20 overheating. They are just bishez sometimes.

[turbocrisper]

have you tried replacing the thermostat mine ran hight temps and stuck occasionally

[Coolwhip]

FYI...the little hood spacer mod has it's disadvantages:

Makes the hood shake at higher speeds.Causes low pressure from the top curculate under the back of the hood at higher speeds as well causing unwanted drag. Good for low speed autox and city driving, not so good for highway driving.

[Cpt_Impossible]

At higher speeds the back of the hood is like cowl induction and air goes in and then under the car creating drag, but also I would think that airflow by the turbo wouldnt be such a bad thing.