I'm starting to think that my overheating issue is internal. Today, I pulled the radiator cap and ran the car. When it warmed up, flow to the radiator looked good. This at least tells me that the t-stat is opening up and that the radiator isn't clogged bad. However, it was foaming up really bad. And when I'd increase the revs of the motor, coolant would literally shoot out of the opening. Someone correct me if I'm wrong, but I think I'm looking at a headgasket or cracked head/block.


Wink
86 NA

 

Is it overheating all the time or usually only when the car is sitting, and not moving?

 

it's not neccesarily a BHG, but that's a very likely culprit. HAve you burped the system a few times? A sure way to check to see if it's a BHG is to go to Napa and get a tester that tests for combustion gases in your cooling system. you just put the tester in place of your radiator cap and run the car for a while. If it turns a certain color, BHG.

 

cafe-au-lait oil whenyou check the oil will also tell re bhg. is it foaming from the thermostat gasket area or from a crack in the block?? has the engine been thoroughly flushed--waterjackets,etc? every 2 years, man--is your fanclutch or clutch fan working properly?? (IS THE ORDER OF THOSE WORDS RELEVANT??)--my 1986 na had a soecial problem--the waterpump belt would scrape the lower radiator hose while hot--the hose bulges, the belt grabs it with acceleration, and then oops--spray when sitting,--good luck.

oh--and listen to zbzbe--she's cuter than i am. and probasbly smarter in these cars than me--i only knows what mine does--all 3 of them.

 

if your radiator doesn't leak, and your coolant recirculation system is in good condition, the next thing to check is your fan clutch. From my experiences, this is one of the most important parts to check. If the fan clutch can spin more than 2/3 of a revolution, there is a good chance that it is bad. Go down to your local parts store, ask to see a new fan clutch for your Z, and feel the resistance of the new one vs. your old one. If there is a noticeable difference, the fan clutch will need to be replaced.

Also, after letting the car warm up, let the car cool down for 15 mins. or so, and pull your spark plugs. Have a friend crank the engine over while you watch the spark plug openings. If any water shoots out, then your head gasket is leaking/blown.

Just a few tips, the spark plug idea won't always work, since the gasket could be blown in a different place than next to the cylinders, like around the side of the block.

Good luck!

 

It really seems to overheat when driving. Temps get out of hand in a hurry. But at idle, it's not as bad.

I've purchased a head gasket kit. And I'm hoping to get to changing them this weekend. When I have the motor apart, I'll be able to inspect the heads really well for any damage. If it all checks out, I'll put it all together and pray for the best.

Oh, by the way, I've got an electric fan to install on her radiator as well. I figure with spending the $$$ on a clutch, why not upgrade as well. Less parasitic losses this way.

 

use a level and make sure your head isn't warped...most of the time when a car blows a head gasket, it warps the head as well. You'll need to take the head to a machine shop and have them resurface it...not too expensive (50-100$)

 

That's the plan. Thanks for the heads up.

I've got my straight edge out and ready for it today.

 

I'm not too familiar with the 300ZX heads vs the 240Z heads, but I'm guessing that they are both aluminum. Be very careful with aluminum heads, you can get near invisible cracks which will not leak when pressure tested at the machine shop, but as soon as the car gets to normal operating temps, the aluminum expands, thus making the crack larger, and water spews out. I had this issue with my e88 head from my Z, where the head held pressure, but would leak when under normal operating temp.

Good luck, make sure the machine shop pressure tests the head if you decide to get it resurfaced.

 

might as well get it reworked if you are going to pull it