Overheating Rb25 180sx

[copycutter]

Hey people, finally got the car back from TTRacing with an rb25det from a s2 r33 gts-t.

The mods i've got are exhaust (with stock r33 dump), pod, intercooler, and a plazmaman inlet plenum. --->

http://i34.photobucket.com/albums/d106/tun...93252553477.jpg

It goes great - extremely responsive, especially because the throttle cable is much shorter and touchier with the plenum.

There is a problem though; Alex from TTR said he drove it to the gold coast to get the thing complied, and when he pulled in the the complier's shop, it overheated. So when he got back the cut out the little grill on my front bar to help with airflow.

Anyway, i also made alex hook up the tacho and temp gauge before id take it. When i was driving back on the highway the temp gauge took ages to start moving, and then only went up like 1 or 2 notches out of about 10. When we pulled in to mudgeeraba to grab a mates rb20 180, and show him the work it seemed fine.

We also drove to another mates place, then around the corner to a car wash to clean her up. Then at about 7, we drove to a 3rd mates house. When i pulled up and popped the bonnet to show em tho, the car switched off and the thermo kept running as per usual i guess. But the coolant overflow bottle started spewing water and coolant out of it for about a minute. We guessed this could possibly be cos the thing was a little overfull, but i was pretty concerned needless to say. Anyway we got to driving to broadie carpark and got there about 8. We all backed in to carpark spaces and then my mate noticed my car dumping a fair bit of water, so we popped the bonnet again and the overflow bottle is steaming and dropping water everywhere.

"F**k!" - was my first thought... Eventually we called out a mechanic mate, who decided we should bleed the system of any air bubbles that could be there. So we got it to operating temp (heater on), and undid the little bolt.. Sure enough, brown water comes spurting out in little bursts with heaps of air. We leave it till the flow turns green, as well as under the radiator cap, and top it up with some good coolant. Now the temp gauge is reading about 1 third of full, so we drive it around the carpark where theres no airflow to see if it overheats. We park it after 5 or 10, and it seems fine. We then drive it about 15 mins to hungrys on bermuda st, where it appears to drop more water only when we stop.

So i drive her home, instead of removing my front bar to see if its really an airflow problem - or just a rooted thermostat/blocked radiator.

Any help would be greatly appreciated guys, i know its pretty impossible to tell without seeing it. Ill call TTR on monday and let em know anyway. Our first thought was to get rid of aircon radiator and get another thermo, but my mechanic mate reckons one 12" should be able to cool it, because the things pretty standard.

Cheers, Nick

[SteveL]

You need to go over the car's cooling system with a fine tooth comb. Was the entire system flushed including draining the block completely ?? (brown water comment suggests not). A lot of these engines sit around for a long time in wreckers yards and cooling system clogs up with crap plus who knows how the original owner(s) treated the car (again - brown water comment). At the very least I would:

- pressure test the system (there's a chance you have a blown head gasket).

- change thermostat

- change water pump (or at least check it)

- completely flush cooling system

- have radiator cleaned and tested.

All of this assumes you have everything connected correctly.

[Al]

Has the radiator been upgraded from the std 180sx to at least the std 33 sized radiator?

There is a BIG differance between "should" and "does". I personally would consider fitting the largest aftermarket radiator, in the allocated space available, with the best high volume thermo fans. You now have 33 running gear, so you need at least 33 cooling.

[copycutter]

It does have a brand new water pump on it now so that shouldnt be the issue.

It is running what i believe to be either an r32 or r33 radiator. Im pretty sure its r32, and its running the one 12" thermofan on the left side of the radiator.

I drove it again today in the heat to a mates place, and it seemed fine. So we drove it around for a little and brought it back to his place - again fine...

I assumed that maybe getting those air pockets out must have helped a bit. So we decided to let it idle for a bit where it gets no airflow with the bonnet down. After about 5 mins the coolant was bubbling in the overflow resorvoir again, but didnt spill cos we turned it off.

I removed the front bar and cruised it home after about 30 mins or so, and it seemed fine. When i got home, the coolant in the overflow was exactly where it was when i started this morning; about 1cm under "MAX". Obviously, the extra airflow at the front helps also, but this problem seems to really occur when the car is sitting with the engine running.

Also, with this r33 ecu hooked up to my temp gauge, does it need any modifying to actually read the temperature accurately. Mine seems to take forever to get moving, and only gets to about a quarter up and stays there, even when the coolant starts to boil.

[copycutter]

And the compression between all the cylinders is between 160 and 154. If the engine had a blown head hasket wouldn't i see water stains down the side of the rocker covers and the compression be off?

[Bl4cK32]

thermos dont work efficiently without a shroud. Ive never seen any other setup work better than the std factory cooling system. If you want thermos, try the el(?) ford factory twin thermo setup with the shroud.

Are u running a std clutch fan, or is the 12" you are talking about the aircon fan?

[SteveL]

And the compression between all the cylinders is between 160 and 154. If the engine had a blown head hasket wouldn't i see water stains down the side of the rocker covers and the compression be off?

<{POST_SNAPBACK}>

I didn't say you had a blown head gasket, I said "there's a chance....", and there always is when you've got coolant boiling, etc.

I've told you what I think, and waterpump wasn't the only thing. If this were my car I wouldn't be driving it until I found out exactly what was causing the issues your having, but it's impossible for anyone here to tell you the exact cause just from a description on the forum (sorry, but that's just a fact)

You now say the waterpump was changed, but I would question how it is that you still had 'brown water' in the system if that is the case. Removing the water pump drains most of the colant....but not all of the block. To me this says the system wasn't flushed completely.....and that the job hasn't been done properly.

[copycutter]

thermos dont work efficiently without a shroud. Ive never seen any other setup work better than the std factory cooling system. If you want thermos, try the el(?) ford factory twin thermo setup with the shroud.

Are u running a std clutch fan, or is the 12" you are talking about the aircon fan?

<{POST_SNAPBACK}>

Obviously i'd prefer to run a clutch fan in a shroud, but in a 180sx the room is fairly limited - so thermos are the only option. The aircon radiator has no fan at all, there is only one 12" thermofan on the rear of the r32 radiator. If need be ill remove the aircon system altogether and run another 12" thermofan on the front side of the radiator. I may also get the radiator cleaned and pressure tested before this also.

[Bl4cK32]

Id say your best bet is to try the el thermo setup with the shroud. They are slimmer than the clutch setup, and will cool better than 2 thermos without a shroud.

[Al]

You stated that it has a new water pump, is it a Genuine RB25 std pump? As the VL and N1 pumps fit, but have less fins, thus don't flow as much water at idle, causing the engine to overheat.

Could also be a airflow problem. May be worth lifting the rear of the bonnet (near the windscreen), using washers, to allow better ventilation in the engine bay.

Also, if the front bar is more restrictive than a Skyline you will need a larger radiator than a std Skyline. I may be wrong, but i think the R32 radiator is smaller than the R33, so you may already caused a heating problem anyway.

Just another suggestions.

Alan

[BH_SLO32]

Obviously i'd prefer to run a clutch fan in a shroud, but in a 180sx the room is fairly limited - so thermos are the only option. The aircon radiator has no fan at all, there is only one 12" thermofan on the rear of the r32 radiator. If need be ill remove the aircon system altogether and run another 12" thermofan on the front side of the radiator. I may also get the radiator cleaned and pressure tested before this also.

<{POST_SNAPBACK}>

As a guide I have a 14", 10" and the factory AC fan operating to keep my R32 with RB25 cool. I have noticed that my temperature is slightly above the half way mark on hot days. The single 14" fan was insufficient.

My previous car had 2x12" fans and the standard AC fan (from memory) and it seemed to cope ok.

My bro-in-law is currently about to fit a 10" fan to his R32 as the recently installed 14" thermo and standard AC fan are not able to keep up with the demands of his motor on these hot days.

With respect to the slow moving and low reading temp gauge I would suggest the RB25 sender unit has a different resistance characteristic to the sender unit used in the factory motor. I had to use the temp sender from my R32 RB20 motor to maintain correct temp readings. If you have the old motor it hopefully will be simply a means of unscrewing the RB25 unit and inserting the unit from the old motor (fingers crossed - I don't know what old motor you had).

Hope this helps.

Cheers,

[copycutter]

Hey guys. Took her back for a re-think all day today. We decided to open the airdam on the ca18 front bar, as well as remove a little bit of the steel support behind it, and the grille between the headlights. All assist with the airflow. We then removed the aircon condensor and radiator - as well as the custom aircon lines that i got made up (lucky we hadn't re-gassed it yet ).

After adding another 12" thermofan to push on the RHS of the radiator, as well as the "pull" one on the LHS of it.

We then re-bled the radiator, and added a ca18 temp sensor to the engine, as obviously thats what the gauge cluster wants to read off of. It now runs at mid-way through the temperature gauge - exactly where the ca18 used to run at. And with the front bar on, and leaving it running sitting for like 15 mins it didnt skip a beat. So i took it for a drive - and fine

So i drove to logan hyperdome to check the temps after driving around the carpark for a bit.. parked and checked - still fine.

I then drove to the airport to get my dad in Brisbane, checked and still fine there, although i still put in about 10ml of water into the overflow bottle as the radiator had drawn it in a bit, but no leaks whatsoever.

I then drove all the way home to Robina on the Gold Coast, and its fine; so my guess is that the r32 radiator seems to be able to cope with the thermal loading that the larger engine generates, but not without the removal of the aircon as a restriction, and creating as much airflow into the engine bay as possible.

Thank you everyone who posted for the quick and helpful ideas, as i mentioned all the possibilities to pinpoint the solution. I asked about jacking up the rear of the bonnet - but apparently this is illegal, because if you have an oil leak it will spill onto the windscreen. This would probably be more helpful to airflow when the car is moving, and the problem was more a stationary one.

Thanks again ppl,

Nick (ill post up pics of the conversion when i clean up engine bay )

[Al]

Glad to hear you found a solution.

I personally couldn't live without the aircon

[copycutter]

Mate honestly i'm the same... lol

But u do what u can to own the RB when you couldnt, and im paying the price - which i consider reasonable compared to owning an sr!

[Cubes]

SR is a damn good motor.

I found in traffic with the a/c on that 2 x 12" fans pulling with the std 12" fan pushing was not good enough, it was constantly spewing coolant out when stationary and when turning off the car.

They 100% need a shroud. If you were to grab some sheet metal bend it up a little, fit 2 x 12" thermos pulling and run soem decent wiring to them I suspect there will be no cooling issues.

With the a/c on and these 40+degree days I've noticed she will hit the occasional 100degree's, sometimes slightly over if I'm stuck in traffic then hit a big hill to drive up. Do note that the std temp guage stays on half from around 72degree's right up until 109degree's, only then will it start to creep up.

A mate of mine fitted a temp guage to his VLT, suprisingly it runs basically the same temps, often hitting 100degree's.

[copycutter]

SR is a damn good motor.

I found in traffic with the a/c on that 2 x 12" fans pulling with the std 12" fan pushing was not good enough, it was constantly spewing coolant out when stationary and when turning off the car.

They 100% need a shroud. If you were to grab some sheet metal bend it up a little, fit 2 x 12" thermos pulling and run soem decent wiring to them I suspect there will be no cooling issues.

With the a/c on and these 40+degree days I've noticed she will hit the occasional 100degree's, sometimes slightly over if I'm stuck in traffic then hit a big hill to drive up. Do note that the std temp guage stays on half from around 72degree's right up until 109degree's, only then will it start to creep up.

A mate of mine fitted a temp guage to his VLT, suprisingly it runs basically the same temps, often hitting 100degree's.

<{POST_SNAPBACK}>

Of course the sr is a damn good motor. But u have to understand that i had a ca18, which aint bad either - but for both to support the 270+kw atw i was after would be impossible for a std motor. So i would have had to trasnplant in an sr AND rebuild it. not feasible...

And if i was to rebuild my ca, which i was very near to doing - if i ever ran a bearing or blew it --> there's all my money gone. This way is more streetable, the 6-cyls make very nice street cars to get around with.

As for the water temp gauge in my cluster, we used a ca18 temp sensor and it appears to work now - behaving itself and sitting on normal. We rigged one 12" thermo to push all the time, and another 12" one to a termostatic switch to pull air through, as well as some major cutting to the front bar and air apertures. There's quite a bit more airflow now that the aircon gear is all gone, (so now she's a windows down girl ). I'm also planning to put a sheet of alloy underneath the intercooler and radiator to stop the air from dipping out and under the car - as the air will take the easiest path in terms of restriction, thus forcing the air to pass through the radiator and engine bay.

Cheers, Nick

[Cubes]

Of coarse the rb25 is a better motor.

hrmm I wonder how GTR-Ben's S13 Rb30DET is going...