Nealio240z Posted September 4, 2007 Share Posted September 4, 2007 I have had this problem for some time now.. Iv replaced my hoses to steel braided, i got a 4 core radiator, and a 160 thermostat. Iv changed out everything but the waterpump. My 1990 350 still heats up on the freeway. Runs fine around town. Could my water pump be bad and show no physical signs? Any help would be appreciated... Quote Link to comment Share on other sites More sharing options...
80LS1T Posted September 5, 2007 Share Posted September 5, 2007 Whats overheating, temp wise? What kind of fan are you running and what kind of fan shroud do you have? This topic has been beaten to death(search), you must seal up the radiator and fan or you will drastically reduce your radiators efficency. Guy Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted September 5, 2007 Administrators Share Posted September 5, 2007 Air flow “to†and “through†the radiator seems to suspect in our S-30 Z cars. The results of the recent wind tunnel tests show the Z car definitely shows signs of having issues in that area. As you, I chased my tail trying to get my V-8 Z to run cooler as it wanted to run warm on warm days, even down the freeway under light to no load where air "should" be flowing through the radiator. In an effort to keep it cool I employed the following mods, and alterations. 1) Blocked off the internal block coolant bypass and redrilled the plug with a smaller hole. 2) Reduced the water pump impeller to housing clearance. 3) Ported the water pump itself, thermostat housing outlet and intake manifold coolant ports. 4) Added a backing plate to the water pump impeller. 5) Port matched the water pump to the block. 6) Over drive pulleys in two steps. 7) Colder thermostats. 8) Special high flow thermostats 9) Higher pressure rad caps. 10) Burping the cooling system using a few different methods. 11) Stock car racing radiator. 12) GM Radiator from JTR. 13) Higher flow cooling fan, (I should’ve went to a REAL fan as I was still using inadequate cheesy cheap-o fans). 14) Removed the license plate from in front of the grill. 15) Removed the grill. 16) Sealed off the holes in the radiator core support . Now the only mods that made ANY noticeable improvements whatsoever in the engine running cooler were the mods that improved air flow “to†and “through†the radiator. All other mods to improve coolant flow made no difference. With what I learned from the wind tunnel testing recently, I feel quite confident that if I would’ve employed some of the principles learned from the wind tunnel testing, the overheating issue in my car would’ve been 100% solved, at the time, I just had no idea what else would or would not improve air flow “to†and “through†the radiator in an S-30 Z car. That’s my $.02 Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted September 5, 2007 Administrators Share Posted September 5, 2007 I have had this problem for some time now.. You didn't mention if this was something that developed over time or its 'alway's been that way'. The more clues the better. If its the latter, maybe your water pump is the wrong one... throughout the years, GM spun the water pump with both V-belt and serpentine... they are not interchangeable, as the direction of rotation is opposite. Quote Link to comment Share on other sites More sharing options...
Nealio240z Posted September 5, 2007 Author Share Posted September 5, 2007 Iv always had the problem... Im using a ford tarus fan and shroud. I have two temp guages- one digital, one not. Does that help?... Quote Link to comment Share on other sites More sharing options...
burrl Posted September 6, 2007 Share Posted September 6, 2007 To fix my V8-Z overheating issue, I just bolted a small air dam (stainless steel) to the bottom of the aluminum radiator core support strap, bent it slightly forward and curled the edges like a scoop. It catches air moving under the air dam (hangs 1/2 inch lower than the air dam) and deflects the air up to the radiator core. I haven't had a problem since. Hope that helps you. Quote Link to comment Share on other sites More sharing options...
datsunlover Posted September 6, 2007 Share Posted September 6, 2007 Your '4 core' rad.. is it a decent size? Also, is it mounted completly vertical, or is is tilted back some? (I havn't done a Z V8 yet, don't know what the clearence's are like..) My 85 RX7 V8 had a major overheating issue when I orriginaly built it, in part, because the rad, a 4 core stock car unit, had to be tilted back (foor hood clearance) which makes for a bit of a problem getting air THROUGH it. Also, I had NO shrouding or duct work of any sort, so a lot of air got around it, and the one electric fan I had pulling through wasn't quite enough. It ALWAYS ran around 200 and over. Recently, I have 'rebuilt' this car, again with a simmilar rad, but now I have TWO fans; one in front pushing, one behind pulling. (just 'junkyard' fans from frond wheel drive cars) The sides are a lot more sealed up, and I am going to mount a piece of stainless up top to stop air from getting over the rad. However, even though the top isn't sealed up yet, I had the car out for it's first road test the other day and with a 160 stat it ran steady around 175-180. I was sitting in traffic and it climbed to about 190 at one point, but I think it will be fine once I finish sealing it off up top. Also, I plan on building an air dam of sorts in the front of the car which should help as well. Oh, you could try some additive too, called 'water wetter' and it will drop your temp by 10-15 degrees or so. (I've run it in a few cars now, and yes, it really works) Quote Link to comment Share on other sites More sharing options...
Nealio240z Posted September 6, 2007 Author Share Posted September 6, 2007 The radiator sits vertical. I just changed the water pump last night and there is no difference in temp...RRRRRRR. made me mad... I got a 160 thermostat and it still runs at 200+ degrees. Maybe I need to direct more air to the rad using some type of scoop? Quote Link to comment Share on other sites More sharing options...
Nealio240z Posted September 6, 2007 Author Share Posted September 6, 2007 I forgot to mention that the engine is a 1986-1994, with vortec heads. I dont know if that is going to help or not... Is this a common problem? I just went for a ride and it did a steady increase in temp up to 240 degrees!!! Could there be something in the engine that is clogged, like a water jacket or the wrong headgaskets? Im at the end of my rope here and dont know what to do about this... Quote Link to comment Share on other sites More sharing options...
MikeJTR Posted September 7, 2007 Share Posted September 7, 2007 What transmission and gear ratio are you using? The reason I ask is because there have been others on this forum who had overheating problems at freeway speeds, and I think it may be due to coolant foaming. If the coolant is foaming, an underdrive pulley may help. Quote Link to comment Share on other sites More sharing options...
bjhines Posted September 7, 2007 Share Posted September 7, 2007 What kind of hood do you have on the car. Have you added vents or a cowl indution modification? Did you seal the radiator to the core support? Improper underhood airflow is known to cause cooling problems at highway speeds. If aiflow can get into the engine compartment without going through the radiator it will overpressurize the engine compartment and stall airflow through the radiator. Quote Link to comment Share on other sites More sharing options...
TimZ Posted September 7, 2007 Share Posted September 7, 2007 I have had this problem for some time now.. Iv replaced my hoses to steel braided, i got a 4 core radiator, Not the answer to the question you asked (Paul and others handled that pretty well already), but did you mean to say you are using SS braided hose as replacements for the upper and lower rad hoses? This is fine so long as your engine is solid mounted, but will fatigue your rad inlet and outlets if the engine can move with respect to the frame. Quote Link to comment Share on other sites More sharing options...
Nealio240z Posted September 7, 2007 Author Share Posted September 7, 2007 Im using a TH-350 w/ 3.90:1 ratio with 27" tires. I run 3000rpm @ 60mph. I have a cowled hood from a 1978 280Z with fiberglass vents... The hoses are internal coiled rubber. Im statring to think that the headgaskets are wrong for the year, or the block is clogged with something... Quote Link to comment Share on other sites More sharing options...
bjhines Posted September 7, 2007 Share Posted September 7, 2007 You say "COWLED HOOD"... This is a KEY PROBLEM! Please describe the hood for us in more detail. Quote Link to comment Share on other sites More sharing options...
Nealio240z Posted September 7, 2007 Author Share Posted September 7, 2007 Its a 1978 280z hood with the "cooling holes" on each side. I replaced the cooling slats with fiberglass vents from motorsports. They face back to the driver and leave a 2" x 4" opening for air to escape... Iv also ran the car with the hood off and the problem is still present but it takes longer to over heat... I just found out that the motor has had alumina-seal through it before. Could it still be clogging something in the heads or block? Quote Link to comment Share on other sites More sharing options...
gretchen/jason Posted September 8, 2007 Share Posted September 8, 2007 Eh i fought the same problem when i used the radiator from JTR . I got a Universal 2 row rad from summit racing got a black max xtreme fan put in a 185 degree stat " yes i ran a cowl induction hood " but even without that hood it over heated with the stock 78 hood . After i added those products i went damn i should try to slow down the flow of the water seeing as im running 4.11 gears with a Th350 3,700 rpms at 60 mph so i slowed down the water flow problem solved . The new rad from summit racing droped me from 230 degrees to 200 !!! Then the slower water flow keeps me around 175-180 with a supercharged 350 . Or it did till i yanked it to do a 383 It seemed the more water i tried to flow the worse it got so the longer it can stay in the radiator to cool off the better it got hence the slower flow so a stock water pump helped as i tossed the high flow pump and got the biggest water pumpo pulley i coud fit on there i believe it is about 7 1/4 inches the crank pulley is about 6 1/2 across Jason Quote Link to comment Share on other sites More sharing options...
strotter Posted September 9, 2007 Share Posted September 9, 2007 I came up with the same solution as burrl - piece of sheetmetal, 8 x 20 or so, mounted to the radiator support, pitched forward so as to catch air moving under the car - though after reading through the windtunnel thread, I may be stopping air escaping from in front of the radiator. Note that my air dam routes the air directly to the radiator, but does not come in contact with the support (as it probably should). In any event, I never had a problem with overheating at speed again. BTW, also using the Taurus fan & shroud. Quote Link to comment Share on other sites More sharing options...
MikeJTR Posted September 9, 2007 Share Posted September 9, 2007 Eh i fought the same problem when i used the radiator from JTR . I got a Universal 2 row rad from summit racing got a black max xtreme fan put in a 185 degree stat " yes i ran a cowl induction hood " but even without that hood it over heated with the stock 78 hood . After i added those products i went damn i should try to slow down the flow of the water seeing as im running 4.11 gears with a Th350 3,700 rpms at 60 mph so i slowed down the water flow problem solved . The new rad from summit racing droped me from 230 degrees to 200 !!! Then the slower water flow keeps me around 175-180 with a supercharged 350 . Or it did till i yanked it to do a 383 It seemed the more water i tried to flow the worse it got so the longer it can stay in the radiator to cool off the better it got hence the slower flow so a stock water pump helped as i tossed the high flow pump and got the biggest water pumpo pulley i coud fit on there i believe it is about 7 1/4 inches the crank pulley is about 6 1/2 across Jason I remember your cooling problem at highway speeds, how you used the JTR radiator, and how you experienced better cooling with the two-row Summit radiator. I always felt that your highway cooling problem was from the coolant foaming because of the 4.11 gears and the non-overdrive transmission. I'm glad you mentioned that slowing the water pump improved cooling. It should be noted that when coolant isn't foaming, slowing the water through the radiator will not help cooling. The fact that slowing the water through the radiator helped your situation is an indication the coolant was foaming. I have made some see-through hose splicers out of polycarbonate, that allow you to see the coolant as it goes through the radiator hoses. I initially made them because of cooling problems with LS1 swaps caused by air pockets in the cooling systerm. These splicers can also be used as a diagnoses tool for coolant foaming problems. The splicers are similar to our brass and aluminum hose splicers, but they are made from polycarbonate, and are longer to allow a window to view the coolant. Quote Link to comment Share on other sites More sharing options...
cobraz240z Posted September 9, 2007 Share Posted September 9, 2007 Maybe your using the wrong year water pump.... Remember some years had reverse flow...... are you runing a serpentine system or v-belt Quote Link to comment Share on other sites More sharing options...
gretchen/jason Posted September 9, 2007 Share Posted September 9, 2007 I remember your cooling problem at highway speeds, how you used the JTR radiator, and how you experienced better cooling with the two-row Summit radiator.I always felt that your highway cooling problem was from the coolant foaming because of the 4.11 gears and the non-overdrive transmission. I'm glad you mentioned that slowing the water pump improved cooling. It should be noted that when coolant isn't foaming, slowing the water through the radiator will not help cooling. The fact that slowing the water through the radiator helped your situation is an indication the coolant was foaming. I have made some see-through hose splicers out of polycarbonate, that allow you to see the coolant as it goes through the radiator hoses. I initially made them because of cooling problems with LS1 swaps caused by air pockets in the cooling systerm. These splicers can also be used as a diagnoses tool for coolant foaming problems. The splicers are similar to our brass and aluminum hose splicers, but they are made from polycarbonate, and are longer to allow a window to view the coolant. Ah ya remember me from that long ago , im not giving the JTR rad a bad name in fact i used it for a few months after i slowed down the water flow . I did reinstall the other rad because i had the aluminum polished to a nice shine for looks . But i still keep the JTR rad at hand just in case . Jason Quote Link to comment Share on other sites More sharing options...
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