Help! Rb25 problems

[specialedition]

Hey guys,

So i just got my car swapped from a rb20 to an 25 s2. So the first day back my problems started!

I was driving back to my garage where i work from the swapshop and the car started to over heat. So i get to my shop in the nick of time pop the hood and what do i find! Black Coolant!

So after i finished work i continuously flushed my cooling system the the following three hours! The Sh*t that came out of my motor was terrifying! Basically looked like my coolant and oil were mixing! Only problem is my oil is super fresh and golden! So i know my coolant isnt mixing with my oil via head gasket or atleast i hope so.

So after 3 hours of flushing i decided to wrap it up with hopes the over heating would stop. i was wrong had to pull over nearing my house 10 mins later as temps spiked.

Anyway so i got the car back to my swap shop that did the swap and they said could be a possible oil leak within the oil cooler and coolant lines. So they replaced it and same problem!

Im a little lost for ideas as i couldnt figure it out and neither could the mechanic at the other shop. Im assuming if i remove the thermostat and flush the block it might solve my issue with the current crap coming out of my engine perhaps even drain the block completely.

Has anyone had issues like this before, or an idead on how to fix this? any help wouldk be appreciated greatly.

Thanks

[Skym]

Sounds like a headgasket leak (oil is getting into coolant).

Can pressure test cooling system via radiator pressure test kit (fits where radiator cap goes). If pressure drops and there's not external leaks, then you sort of have found your problem.

Thermostat is easy to check, as bottom radiator hose would be cold (compared to top radiator hose) when you touch it. That's when engine is up to temp.

[specialedition]

Thanks for the reply skym

I checked pressure and it holds which is a bonus, along with there is no coolant in my oil. No i brought my car to another shop to get it pressure flushed as the regular was wasnt doing it! turns out there was a lot of crap in the motor from transport im assuming.

So now i got my car back with fresh coolant! i drove it back home ( 25 mins) it didnt over heat on the highway, the second i got off the highway my temp on my greddy gauge started to climb. Im starting to think or im hoping its just the thermostat is faulty maybe not opening fully and or perhaps i have a head gasket or cracked head as the issue.

As of right now there is no more black stuff in my coolant and no coolant in my oil. Does anyone know if i can use a thermostat from a 240 or a 300zx?

Thanks

[nick-nismo]

300zx works, use oem though
what are you using for your cooling system, still have the r32 gtst rad? are you using the clutch fan? is there a shroud?

[specialedition]

still using oem set up for the r32. Im certain the thermo is working because on idle top rad hose is hot and lower rad hose is cooler. its only when i start moving under load that the temp seems to climb. Although i went on a 25 minute drive and the temp peaked at 95 degrees on my greddy gauge.

I also removed the rad cap and tried to get all the bubbles out of the system but it just continues to bubble so im starting to think head gasket is the issue.

[Rblove26]

I would make sure you dont have a air trapped in your cooling system first, just wondering if you have take the bleed valve out thats between the head and intake manifold.
dont have a picture of mine, but here's similar

http://www.skylinesaustralia.com/forums/topic/164805-does-radiator-need-bleeding/

also while your bleeding it, have your heat on high and make sure your getting lots of heat, if it goes cold from time to time then you know there is still an air pocket
good luck

[specialedition]

Thanks for the reply Rblove26, i will definitely look into this tomorrow! I appreciate the responses everyone hopefully it is just an air pocket! Will update tomorrow!

[supersayianjim]

was the coolant black or dirty brown



like this??

[specialedition]

it was super black, not like the pic you posted above!

Update: i bled the head this morning before leaving for work. It had no air in it as coolant started coming out instantly once i started the motor. I drove the car to work (25kms away) and it was sitting at 82.5 degrees which is still abit hot for my liking. Then drove it home and it reached 100 degrees with the sun and warmer weather.

i think im gonna try and swap thermostats see if it makes a difference it might solve my problem.

Thanks

[h4X6]

Head gasket. If you coolant is not clearish and it's brown/black you have a Headgasket leak.

Sent from my Z10 using Tapatalk 2

[specialedition]

Thanks for the reply H4x6, The only problem is there isnt any coolant in my oil. And after the coolant flush there hasnt been any oil in my coolant. My coolant is clean still maybe a bit dark green but still green none the less.

Either way now im bringing the car to the jdm shop i bought the engine from they are gonna sort it out. Perhaps a new motor will be installed if the head gasket is the issue

[Skym]

Should be bright green. Also don't mix coolant brands and flush heater, etc of old coolant and run recommended coolant from Nissan.

You're welcome. What I mean when engine is up to temp and the top radiator hose being warmer than bottom radiator = thermostat not opening when it should. That's what my car did when thermostat failed and started to late open at around 95 degrees+ when tested thermostat in hot water afterwards. Water level dropping in radiator is another symptom of failed thermostat.

If thermostat late opens it can overpressurise the cooling system and headgasket can let go (one of the weakest points).

Also stock radiator does block, as my cars radiator was I think around 15-30% blocked (from memory of the 2x I had it checked, cleaned). It involves removing top or bottom tank and rodding core to clean it properly, fit new gasket to top or bottom tank. Can do it 2x, once with top, once with bottom tank. Why you do it once top, once bottom is because the tabs that you bend over can break if do it too many times.

Stock should be around 76.5 degrees C when thermostat starts to open and fully open at around 90 degrees C and idles around 79-80 degrees C which is normal (factory figures). My car would sit at around 82 degrees C when I lasted tested it (years ago), but that was due to a ECU tune problem. When stock it was 79-80 degrees C. Around 84 degress C is common for RB25DET at idle once modified with stockish cooling system.

[specialedition]

Thanks again for the reply Skym,

My car does idle at the temp anything more then idle the temp will rise above 95+ over a short period of time, at this point i cant even boost considering im still using the r32 gts-t fuel pump i run lean very quickly. I showed my step brother who came over for dinner the car. i started it no rad cap and it just bubbles away every 2-5 seconds theres a air pocket that comes out.

My coolant has become darker as well with black seeming to be in the mix. So im certain the head gasket is the cause for this.

i will be driving the car back to the jdm shop tomorrow so hopfully i can either get a fresh motor or the problem can be fixed

[Skym]

You're welcome. It could be cylinder to coolant gallery. But if it was, engine should run very rough at idle (or could be a small leak that shows up after a long drive). You can crack the block, head if ran cold water through a hot block, head when flushing engine or cylinders are alot hotter than coolant (run engine lean). In future when servicing, should leave it overnight to be safe, flush when engine is cold.

R32 GTS-T fuelpump is 135lph, same as what's fitted to R3325T for RB25DET. But fuel pump could be on the way out (check fuel pressure), fuel filter is blocked or close to.

Bubbles can be caused by waterpump cavitation at higher rpm (N1 water pump reduces creation of these bubbles) or headgasket leak.

[specialedition]

then i guess my motor has more then one issue! i didnt get a chance to return the car to the shop today so ill be doing so first thing tomorrow morning. I just checked my coolant levels and oil levels and preparing fluids for tomorrows long drive. Turns out my oil is lower then it should be along with dark spots in my coolant so! i know what argument to bring up tomorrow!

Skym thanks again for all the answers and responses! youve helped me out quite a bit! hopefully i can get a new motor in my car