I have a 97 Z34 3.4 with a cooling gremlin. The fans come on, I put in a new radiator cap, a new thermostat and the antifreeze is Green.( there appears to be little bits of particulate in it though). My issue is that the heater works fine, so the coolant is moving around. I'm not sure where the sensor is...any other ideas? compression check?

 

BTW, I have a new "bleeder" coming in a few days to see if that helps, the existing one is broken. The PO said they did a water pump, one head gasket and a intake gasket. Basically the car overheats on highway use and intermittently on street driving. When the temp gets high I need to rev the engine to about 3000-3500 RPM's for a couple seconds and the temp backs down again. The belt tension seems appropriate with little deflection. Any ideas would be great....thanks.

 

Since you have to revi t up to get the Temp down ... that sounds like a Water Pump to me!

Either that or you need a thermostat. But, since the temperature will come down with moving the Pump faster ... I think you have a Water Pump that's going!

 

I just did the thermostat yesterday, I replaced it with the 195 Superstat I think it was. I was thinking water pump too, but, the heater works fine so it made me think the pump was working okay. But, after replacing the thermostat and having the same cooling issue where it will cool down if I rev the engine had me thinking twice about the pump. It seems like there are no issues while idling before driving. If I get off the highway and sit in traffic immediately after, I need to increae the RPM's to not overheat.Normal city driving is better due to thefluctuation in RPM's.Is it more likely a water pump or wouldit be beneficial to try and flush the coolant system? The PO thought the system had air in it since he said he changed the water pump already. I thought I read somewhere the pumps are reverserotation... is there a chance the wrong one was put in? I am absolutely unfamiliar with the 3.4...I'm kinda grabbing at straws here, but the repair manual is not that helpful with this.

 

the guy saying he thought it had air in it doesnt put much faith in hismechanical skills. it's a must that you bleed the system. it's worth lookingat. sounds like a pump problem though or a hose collapsing internally.

 

He did bleed the system, however, he did it with a broken bleeder screw. I'm not quite sure how that worked out aside from removing the entire bleeder and getting a face full of coolant when the tstat opened up. I will have my new bleeder in a couple days...it was three days out from GM. I will bleed the system once I get it and check the lower hoses...uppers are new. If that doesn't work, I guess it'll be time for a water pump. Thanks for the help.
Ironically enough, the PO was a mechanic

 

i have heard that there are two kinds of water pumps out there and the new revised pump isnt up to the task. you need a rebuilt older one or a GM OEM one. not a simple part store replacement... these 3.4L's are very picky... but very good engines.... if you are in the florida area, we should meet up... i have a tuner for these cars... and i could reset your fan turn on temps to help eleviate the over heating issue some.

i also highly recomend using a 180* thermostat in these engines too. i personally run a 160* in the summer but i have heard issues with the 97 and a colder Tstat. so i say 180* is as low as you should go. make sure the spring of the Tstat is down facing the engine... also the temp sensor is in the lower intake manifold pretty much near the Tstat housing but underneith that valley. if you go to my webpage and flip thru the site you will find plenty of engine bay shots. z34phoenix.piczo.com