crazy280 Posted August 29, 2005 Share Posted August 29, 2005 I searched this but found nothing. I went for a drive Saturday, and it was really hot, so I opened the floor vents on my '73 240z (you know the knobs just under the dash on driver and passenger side? I'm NOT talking about the normal vents for heat and a/c. I'm talking about the small round knobs that you slide in and out to open and close the flow of air to your feet). After driving on the highway, I noticed the car was running much hotter than usual. When I stopped, I checked the engine myself to make sure the gauge wasn't misreading the temp. Yup, the engine was super hot. On my way back home, it was still running hot, so I got an idea and closed the vents. Soon after I closed the vents, the engine temp went back to normal. I've tried this again since, and it has the same effect. Maybe these vents are drawing air away from the radiator and into the cabin? Anyone ever heard of this? Any input would be great guys. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 29, 2005 Share Posted August 29, 2005 The hole in the front of a Z for the radiator is GIGANTIC. The idea that you could somehow alleviate so much pressure in that area that it would make the car run hotter is not realistic. Look right in front of the radiator. There is another gigantic hole that lets air pass down underneath the radiator, and that huge hole will let way more air past the radiator then the little vent holes will. You need to check into your cooling system for sure. If your thermostat is working correctly and you aren't losing coolant, then the prime suspect would be corrosion in the radiator tubes. Here comes trouble once posted about using Jet Dry in the radiator to get rid of the corrosion. You might try searching for Jet Dry. IIRC the idea was to drain the coolant, fill the cooling system with distilled water and add a bottle of Jet Dry, drive for a couple days, then drain flush and fill with new coolant. Quote Link to comment Share on other sites More sharing options...
2126 Posted August 29, 2005 Share Posted August 29, 2005 Sounds like you're correct in your assumption. Air will flow in the path of least resistance. I think that when you open the vents, the air pressure in front of the radiator drops slightly......hence, less air flow through the radiator. You may consider flushing out your cooling system and if you have a clutch fan, check it for proper function too! Quote Link to comment Share on other sites More sharing options...
crazy280 Posted August 30, 2005 Author Share Posted August 30, 2005 jmortensen: Gee, I've never looked at the front of my car before... *sarcasm* But seriously, sorry if this sounded like a "help I'm overheating" post. Really my Z has no overheating issues; never has. I gave it a new thermostat, water pump, temp sending unit, and hoses when I bought it, just to be safe. The car does not have any overheating issues....UNLESS I open those vents (and even then it never quite boils over, it just gets extremely hot). I could easily demonstrate it if you guys were able to ride with me, but I guess that's the limits of the internet But still, has anyone noticed this before? Where do these vents draw in air from anyways? Thanks Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 30, 2005 Share Posted August 30, 2005 The vents draw in air from right at the top corners of the radiator support. You know those little black plastic elbows? That's what they're for. They take the air from the front of the radiator there and force it into the frame rail thingy underneath the top of the fender, then route it to the vents inside the car. With all of the other holes around the radiator I'm still skeptical that opening those little vents could cause problems. I suppose you could block off the little holes under the elbows with a piece of cardboard and see if that fixes the cooling issue. I'd be surprised if it did... Quote Link to comment Share on other sites More sharing options...
crazy280 Posted August 30, 2005 Author Share Posted August 30, 2005 Ah, I was wondering what those black tubes were used for. I guess they are pretty small holes. Still, it is enough to significantly raise engine temp when I open the vents up. I've been using the vents to warm up the engine in the morning quicker LOL. Oh well, I guess I'll just have to keep them closed. Thanks guys. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted September 2, 2005 Share Posted September 2, 2005 I would still suspect the cooling systems is not up to 100% and opening the vents are causing just enough airflow loss to push it over the edge. This is not normal as my trippled, high compression L28 in a 240 with stock cooling systems (no shroud) does not even run hot on 98 degree days in traffic - and I never shut those vents. In my experience the radiator probably is a little clogged up internally. I would take it to a shop and have it flushed or at least take a look down inside the radiator tubes and see if they look clogged. Cameron Quote Link to comment Share on other sites More sharing options...
crazy280 Posted September 3, 2005 Author Share Posted September 3, 2005 If I start to have any cooling problems, I will check the radiator. But my car never runs hot with the vents closed. Ever. Quote Link to comment Share on other sites More sharing options...
VRJoe Posted September 3, 2005 Share Posted September 3, 2005 It sounds like you need to shroud the front of the radiator. If opening the vents pulls too much air from the radiator, then you need to see why it's not flowing enough through the radiator. - Joe Quote Link to comment Share on other sites More sharing options...
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