LOL at above 2 posts *nods head in agreement* Rant/ A good M8 of mine races a 289 Mustang in Group N. Its a fairly potent little 289 @ 680 Hp @ 8400rpm. Cooling is ALWAYS an issue. The simple (bandaid) solution was to plumb up the original heater core and duct the hot air away and the car via the gearshift hole!!! The low pressure area under the car draws hot air thru the heater core in addition to the usual ram inlet. I can also concur with this. My old V6 Capri (god i miss that car....) always had overheating issues in traffic. Ignoring the actual reasons as to WHY it overheated, (Im a little wiser now than I was at 17) the trusty heater trick largely dealt with the issue! was a little uncomfortable on hot sydney summer days but a small price to pay. The heater bypass issue is real and valid, ESPECIALLY if the system is marginal to begin with. My 125cc superkart uses an inline thermostat. It only has a small, prolly 1mm bypass hole to allow for de-aeration and a poofteenth of water flow so hot water actually get there at all! The engine would run up to very hot and then the thermosts would suddenly open dumping a larger slug of cold water into the engine and Pffft... cold seizure....... A real problem with Nikasil bores and..and...another day perhaps! After much buggerising around, I found the diameter and therefore flowrate of the bypass hose was crucial to the correct operation of the cooling system. Too small and the sudden and late opening of the thermostat resulted in the dreaded thermal shock. Too large and the engine would warm very quickly and less of a thermal shock when the 'stat opened which is yay but overheating at high power levels due to greatly reduce water flow available thru the engine. Moving on, An unrestricted 16mm ID pipe/hose system will bypass a huge amount of water between the discharge of the pump and the pump inlet under pressure. And PLENTY of pressure is available from a centrifugal vaned pump, otherwise needed to be sent to other areas that actually do something useful cooling wise. The cooling system is designed with operate certain pressure/flowrate limits to maintain certain water flow thru different sized orifices in the head gaskets and so-on. You might notice over time that later generation head gaskest often show significantly different restrictors/orofices in place as, over time of the development of the engines, which will run to many years AFTER the introduction of the engine, the designers alter the waterflow to different parts of the engine to help cure whatever repeated cooling system failures they encounter over the R & D timeframe of a given engine. I digress again! The fluid will always follow the path of least resistance and in the case of the water system could provide a sufficient pressure drop to almost stall the watwer flow thru some of the smaller orifices in the gaskets which are designed to force more water to other areas of the head and block. "IF" the water boils locally adjacent to these low flow areas due to a design fault with the gaskets/whatever and reduced flow available due to an unrestricted bypass, the entire cooling system can eventually become aerated with tiny air bubbles which can be enough to cause cavitation of the water pump. Thes especially if the design of the inpeller blades is marginal. The bubbles can...whats the word?? "combine" (will do) into larger bubbles that can also collect at high points subject to reduced flow, evenyually releasing into the water flow further compounding the issues!!! Cavitated water pumps lead to reduced output, lower discharge pressures, further reduced flow in those low flow areas and a further locallised boiling.... and so-on and so-on........ ad-nauseum. So, Im with the Kiwi on this. Why not just at least TRY GENTLY pinching off the heater bypass loop temporarily with some vice grips and note any changes in cooling system behaviour. See what happens before getting too funky! L8r E /rant
Definitely worth further investigation due to an uncharacteristically coherent argument from the shagger. I see what you are saying, and I think a small loss is possible, but like most cooling problems it is often more than one thing that brakes it back, and alleviation is a long way from solution, as you said the system would have to be on the edge already for something like this to have an effect, the system is designed to flow in such a way with one big difference and IMO has nothing to do with flow rate, what it has to do with is the water returning from a heater core has cooled the water being routed to the beginning of the cooling circuit, where as a bypass mod returns hot water to the beginning. What I also get from this exercise is that pre under plenum bypass the turbos are probably seeing cooler water after it has traveled through the small pipes and throttles which are somewhat air cooled, mind you with the above argument in mind the turbos will be returning VERY hot water to the beginning of the cooling circuit. This is why I am such a big OEM fan, Nissan has done some wonderful work that is often not a standalone solution but part of a wonderfully integrated and designed machine, they have also had the benefit of service feedback of thousands of cars in varying environments. I am not saying you are right or wrong, but I much prefer this kind of interaction with you Glenn, it makes me think and helps me and everyone else learn and furthers our joint cause, the understanding and ownership of the 300ZX. Hopefully you will take what I have added and add it to your thoughts on this subject. In relation to the thread and the OP's problem, it is not a crap shoot with winners and losers, it is about a diagnostic procedure, reading his first post, what I saw was highway speed cooling problems, this says to me serious cooling capacity issues, my best guess was a flow problem, the first and most likely cause given the information he provided was a restricted lower hose, I still think this is the most likely key issue, and just a starting point, not a definative answer. He has a hose on hand so easy to test, I am not sure what part the radiator plays in this situation if any, but the first port of call when a new problem arrives is "what was just changed", we have posters saying I have a new miss fire and I recently changed my spark plugs but are off chasing demons elsewhere (possibly causing more problems in the process), and then you have a nightmare, 2 related problems at once, shortly followed by stuff this I am selling my car. Where is Anti up to with this anyway ?
Hey Martin I replaced the clutch fan in my car today and it fixed all my problems. While I was doing this I thought of something else for you to check. It's simple and you most likely have already done this but..........when I installed my 56mm radiator, one of the things I had to do was to shorted the upper radiator hose. If this is not done, the extra length can cause it to fold and it's not always very noticeable. Also I noticed you didn't come pick up the OEM radiator, let me know if you still need it.
He's prbably half way to Dubbo by now lols I may also keep my thermo fan as it did such a great job . Also less load on the waterpump and engine power . With basically next to no mods I need all the horsies I can get
I'll be changing the radiator first, then if that doesn't work I'll be going to the clutch fan. I wasn't able to get the thing registered in time for Zedfest, so there was no need to hurry over and pick up that radiator. It's still at the engineers in Narellen. I'll be picking it up late next week and tackling it then.
May have already been covered but anything against thermo fans? electric fans? I have a 15" on mine and it pumps air like there is no tomorrow, also due to the fact it is bolted straight to the radiator there is no issues about air being lost elsewhere (without a shroud etc) I also think it just makes the engine alot cleaner and nicer..... plus safer lol... can get in and play with all the belts, PS, alternator etc without having removed anything.
Yeah 100% sure. I don't know the figures off the top of my head but the factory clutch fan will flow in excess of 3000cfm... you won't get near that with a single 16" puller fan despite what you read on ebay or twinturbo.net haha.
+1 .... Commodores have adopted this and im sure for good reason . I have never had issues with the V6 motors overheating or cooling issues . But I do remember the old clutch fans on the 202's in the VB - VK's etc where I recall the cooling situation back then was dicey . Now that I think about it I may even investigate with a VT fan/shroud setup .
stick with clutch fan. Investigated this with my TT slicktop. 3500cfm on idle the clutch fan pulls. Highest available 16" thermo is 3630cfm. No room for twins on a TT radiator.
zirgo 16" s-blade 3630cfm. Imported from US vendor. Found flow sheets when investigating for my TT. Probably means nothing as was conducted by manufacturer Still nothing on the OEM clutch fan at revs
it doesnt couldnt unless its 145% YOUR ANSWER IS INVALID please restart your computer and have a teaspoon of sugar.
It's closer to 5000CFM at full lock and good RPM. The best electric fans out there were in the mid 3000s and they cost heeeaps. Some were mid 2000s and still expensive. Majority seem to be about 1800-2000 from the last time I looked around. MoulaZX
It not at revs when you need it but, at revs means you are driving an thus plenty of air flow. You want it at idle when sitting at lights.
honestly it appeals to me but after everything I've read about them the thought left my mind as soon as it arrived. no thanks.
Ashspec has a 16" SPAL that flows 2460cfm .. but even if it was 3000cfm I would still use the clutch fan .(as I am) http://www.ashspecz.com/shop/prodInfo2.php?prodID=51
