aarang Posted September 12, 2009 Share Posted September 12, 2009 Just wondering about the water pump you are using, is it the stamped steel aftermarket impeller type or the Nissan cast impeller style. I had cooling issues at low speeds until I bought a genuine Nissan water pump ( cast impeller) and a genuine Nissan thermostat. I have dual 12" electric fans with a shroud and an intercooler that is the same size as the radiator (stock radiator) and my temps never go over 185 deg now, even when we had 105 deg temps here in Portland a while back. Aaron Quote Link to comment Share on other sites More sharing options...
ktm Posted September 12, 2009 Share Posted September 12, 2009 Hey, just wondering, but wouldn't that defeat the purpose of the bypass if that water doesn't go through the radiator, just right back into the block? I'm not 100% sure that's right, correct me if I'm wrong. You need to read the cooling sticky at the top of this forum. Zmanco, others have already chimed in regarding checking the radiator. I would suggest reading this thread http://forums.hybridz.org/showthread.php?t=153044 on the Gen I Chevy forums. It is discussing a hot running 383, but the principles are the same. Quote Link to comment Share on other sites More sharing options...
FlatBlack Posted September 12, 2009 Share Posted September 12, 2009 You need to read the cooling sticky at the top of this forum. Well I've read it but I guess I didn't understand it fully. I'll try to make it all the way through it again tomorrow if I get time. Quote Link to comment Share on other sites More sharing options...
pallnet Posted September 12, 2009 Share Posted September 12, 2009 I forgot to mention that if you're rad. has some miles on it and the coolant came out looking more like "swamp water" then coolant, I would have it boiled out at a local rad. shop. If you have a buddy that works at an auto shop then pull a favor and have him make the call to the rad. shop for you to drop it off, pay for the job and pick it up. This will get you a few bucks off the job because they will charge the shop rate.. BTW: I ran 8.9:1 compression ratio and turbo with my car. I had one cooling issue when I had the 76 hood in mid summer heat with a slight rise in temps, I went to the 78 hood with vents and with the other things I had done, the car was driven often in over 100' summer heat in southern Louisiana with no issues from that point on. My cooling mods: Local built 4 core rad. made from a stock rad. Large Hayden electric fan infront of the rad. on a thermostat switch. Nissan water pump Pink coolant extra long life (borrowed from work, don't tell anyone) New Nissan thermostat Oil cooler (custom job made from a 83 Jaguar cooler) Hood vents Hope this helps. Quote Link to comment Share on other sites More sharing options...
Tony D Posted September 13, 2009 Share Posted September 13, 2009 "A little bit of detonation from 4K on up" can blow a head gasket to the coolant side just as quick as you read this sentence... DO NOT recirculate the #5 & #6 clyinder head vents to the inlet of the pump, that is NOT where they are supposed to go! They go to either the radiator, or the lower theromstat housing. Ideally.... well, there is another thread dedicated to all that stuff, so I'll skip repeating it here. Quote Link to comment Share on other sites More sharing options...
RUZN Posted September 13, 2009 Share Posted September 13, 2009 I was going to say waterpump...... but if you checked it was good then I had a faulty thermostat that was brand new. give your Coolant hoses a squeeze like your pumping a heart it will help remove air and rev her up and down as you fill the coolant youll notice it drop and rise... you'll spill some but at least youll get all air out. Quote Link to comment Share on other sites More sharing options...
Careless Posted September 13, 2009 Share Posted September 13, 2009 Just wondering about the water pump you are using, is it the stamped steel aftermarket impeller type or the Nissan cast impeller style. I had cooling issues at low speeds until I bought a genuine Nissan water pump ( cast impeller) and a genuine Nissan thermostat. I have dual 12" electric fans with a shroud and an intercooler that is the same size as the radiator (stock radiator) and my temps never go over 185 deg now, even when we had 105 deg temps here in Portland a while back. Aaron Nissan now uses stamped steel impellers on many of their water pumps. I have had both versions of nissan water pumps. Can't say I saw a difference though, but I'm sure the design does do something to flow for sure. Quote Link to comment Share on other sites More sharing options...
SATAN Posted September 13, 2009 Share Posted September 13, 2009 "A little bit of detonation from 4K on up" can blow a head gasket to the coolant side just as quick as you read this sentence... It took me a good 20 minutes to read that sentence. Common knowledge time. Advanced timing = cooler water temps. Retarded timing = hotter coolant temps. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted September 13, 2009 Author Share Posted September 13, 2009 Thanks again for all the thoughts and suggestions. At this point I do not think there is any exhaust leak into the cooling system as I've driven for extended periods and while the temps fluctuate a lot more than with the old motor, they are not out of line I suppose. As I mentioned before, the water pump came over from the old motor and has around 20k mile on it. I had no cooling issues like this on that motor. The radiator was purchased new and has no more than 40k miles on it, always with around 50% coolant. It's possible I suppose that it's the cause, but it seems unlikely. Moving the outlet of the 5/6 cylinder cooling mod to the intake on the passenger side didn't appear to make a difference so I'm going to move it back. I may have to pull the head anyway so would get a chance to be sure about all of this. http://forums.hybridz.org/showthread.php?p=1068258#post1068258 The 2 12" fans I have are slim to clear the AC compressor and were ok for the old motor, but probably didn't have much reserve capacity. There is no shroud. I was hoping that in stop/go driving where I didn't expect to use much boost that this setup would still be ok. But given I'm pulling the AC, I should be able to fit the Taurus efan so will probably go that route over the winter. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted September 13, 2009 Share Posted September 13, 2009 One of the best things you can do at this boint is put a shroud around your fan to insure it is pulling all the air through that it can, and sealing any possible areas that could cause air to 'leak' around the radiator... Numerous posts about lack of shrouding and overheating.... Quote Link to comment Share on other sites More sharing options...
Zmanco Posted September 13, 2009 Author Share Posted September 13, 2009 A shroud would be great, but with the limitied clearance and the 2 12" fans that's not easy. On my last engine I had plugged all the holes and once I'm sure about the intercooler piping I'll do the same again. I agree that maximizing the airflow over the rad is the key. And the Taurus fan comes with a shroud IIRC, doesn't it? Quote Link to comment Share on other sites More sharing options...
Tony D Posted September 14, 2009 Share Posted September 14, 2009 Nissan now uses stamped steel impellers on many of their water pumps. I have had both versions of nissan water pumps. Can't say I saw a difference though, but I'm sure the design does do something to flow for sure. Be VERY careful about comparing what is in a NEW DESIGN and one that is over 40 years old... I have NEVER seen a cast impeller eaten away to a nub after only 6 months in coolant that has gone acidic. "Oh hey, it's a new water pump, I just installed it last fall before I put it up for the winter---can't be that!" Pull pump, stamped impeller was rotted to nothing but vestigial nubs on the bearing shaft. This has happened more than once to cars I've worked on (L-Engines). I will not run a stamped impeller any longer because I feel I can't trust their reliability. I test my Ph 2X annually, and have seen corrosion on stamped impellers that scares me in my own cars, so they are a definate NO NO for my list of things to never use unless absolutely necessary! Quote Link to comment Share on other sites More sharing options...
Daeron Posted September 14, 2009 Share Posted September 14, 2009 Do you use distilled water to add to the coolant? Rusted out impellers are nefarious gremlins to track down.. Can you feel any surge of pressure in the radiator hoses when you rev the engine, while it is hot? Are there any clues to objectively reassure you that you have abundant water flow? I hate to point you towards this, but other than a possible lack of positive fresh airflow over the radiator, the water pump seems to be the likely culprit. Quote Link to comment Share on other sites More sharing options...
woldson Posted September 14, 2009 Share Posted September 14, 2009 I had a Honda impeller that would come loose from it's shaft randomly for about a year, drove me nuts. It was a stamped steal one. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted September 14, 2009 Author Share Posted September 14, 2009 I had to pull the head last night for a different reason and didn't see anything obviously wrong with the HG. I'm gone all week but will look more closely when I return. So far I don't understand why the temps fluctuate so much more for this engine than the old NA given so many of the components are the same. But the original issue of overheating is now gone, so I'll assume it was due to some combination of poor airflow (AC core and no hood) along with perhaps some air trapped in the system. Quote Link to comment Share on other sites More sharing options...
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