I am having a very frustrating problem with my Z. Under normal highway driving and cruising around town(maybe 5psi of boost) everything is fine. When I lay into it on 16-20 psi the temperature is ok then I let off for 10-30 seconds then all of a sudden the temperature goes crazy(about 245*) This motor was built last spring(pistons,rods,bearings, etc) and it ran ok on 16-17psi for the most part but still had cooling issues off and on since the rebuild.

This spring we replaced the turbos since they were smoking and finally tried to get a highboost tune. What we found was anything over 16psi would cause the car to overheat and **** all the coolant all over the place. We determined that the heads were either lifting or the heads were warped so we tore the motor apart, had the heads checked and resurfaced, new head gaskets, and seals done.

Strapped it down on the dyno last week and it was fine, made great power on 21psi, zero overheating. When its on the road and you go into boost its doing it all over again and overheating. I have the APS Extreme TT kit, built motor(2nd one), E85 setup, Proefi, and the list goes on and on. I dont feel its an issue with the radiator being insufficient since im on the stock radiator and t-stat and its usually fine on 16-17psi but no so much anymore. I feel that an air pocket is being created in the cooling system everytime I go into boost. I lose my heat and the temps go straight to 245* and shoot the coolant all over.

I dont know if anyone else has had similar issues but Im beyond frustrated with the situation and just need some good input as to possible solutions.

Thanks!!

Ryan

 

air in the cooling system?

is so, possibly headgasket, or cooling system needs burping

 

Theres definitely air in the cooling system... only after I go into boost. Ive spent hours bleeding the air out of the system on the rack, at an angle on the rack, and just on the ground. I rev the motor up, squeeze all the house, have the heat on high, etc etc... Its got brand new cometic head gaskets and L19 head studs. Im just trying to think of all possabilities... should I just bypass the whole heater core and eliminate that out of the system? Its pretty much a drag car now so heat really isnt important to me. What about the possability of some cavatation being caused by over spinning the water pump as I accelerate? Idk, I doubt thats it im just trying to think of all possabilities here.

 

i would upgrade the rad and fans. If u pushing that much psi I dont see how the stock rad is going to cool everything down in the HOT summer months.

 

Cometic gasket is meh at best. Why not HKS, or HR gasket if the block is cut for it? Definately sounds like the heads are lifting. I assume you are being tuned by SP because you're in Chicago and running Pro EFI. What do they have to say?

 

I too agree that it could be head lift

 

Could be steam pockets also once coolant temps get high enough. Are you losing coolant - could be a leak, letting air in? If you have used the spill proof funnel and you feel the air is out, then it's probably head lift. Next time around you may want to choose the HKS headgasket and use waterless, pressureless Evans coolant.

 

Yea the cars at SP. I asked them what they thought about Cometic vs HR head gaskets and they said to definitely go with the cometics since they havent seen or had any problems with them. I highly doubt its lifting the heads with the L19's, Ive never seen that on those studs before. What are the chances of having 2 different sets of head gaskets go bad within a year? The first time I only got 900 miles and 3 months of driving out of it before it started overheating all the time when going into boost. Now it was put back together with resurfaced heads and new head gaskets and its having the exact same issue and Ive only got about 90 miles on the motor since it was rebuilt. SP is swamped with work and short handed this week so I dont think they will be able to look at it until next week. I just hope we can get the issue sorted out once and for all, its beyond frustrating...

 

Just curious if you've got an oil cooler on there? The air's getting in somehow. I do believe there have been other failures with cometic, but you may want to research it to confirm or refute if you want to stick with that, again.

 

so bumping an old thread. 20/20 hindsight shows that the OP was pushing water due to some sleeve walk under high boost. Apparently, it seems to be a common problem >700whp at least with a few shops that build a bunch of cars. Maybe one of our AZ friends can chime in about thier tune the other day...

Either way, I've never heard anything about our cars pushing water at 700+ whp. The theory is that the open deck sleeves walk just a bit, enough to open a gap by the headgasket allowing exhaust gas to pressurize the coolant system.

I know there are not many VQs pushing 700whp, sleeved or unsleeved but has this been other people's experience?? It was portrayed to me as common knowledge and a real eye opener based on the # of cars that exhibited it.

with threads like this https://my350z.com/forum/forced-indu...ll-cold-2.html it makes it hard to tell whos really pushing water or just had other cooling issues.

 

A stock radiator is NOT enough!! Get a 53MM Koyo not the slimline 36mm. ASAP. You have been informed....now go get that radiator!!!!!!


website: http://www.koyoradracing.com/product...sp?make=Nissan

 

This would explain the cap letting off, but are you sure that's applicable here since the OP described a big temperature spike. If it was spike, then blow, I don't think your description would fit his problem.

 

hmm wonder how common that is in vq's got me a tad antsy now especially since im sleeved

 

I had the Koyo and still pushed some water.

I don't attribute it to a rwhp number (i.e. not a heat issue)...cause at 706rwhp I had zero issues (21psi)....above 22psi it would start pushing water on the 60mm turbos (never did it with the 54mm turbos at 30psi and 768rwhp).

Almost wonder if the cylinders were mushrooming up there.

Tom