so you think you can diagnose cooling system issues?

[grandma's koukis]

Hello folks, I'm newly registered but not new to lurking, however I've come across a problem that I would like at least a second opinion about before I go throwing cash at my car.

Yes, I've searched. Then I searched some more.

This would've been posted in the tech section but as you're all aware that is down.

So here it goes.

Mishimoto radiator flushed multiple times, along with block.
New thermo
New temp sending sensor
New fan clutch, NO shroud or efans

Had shop bleed system, then shoot it with a laser temp gun. 240 degrees at the head.

Took it onto the freeway, overheated after about five minutes. Turned off, waited a minute, turned back on. Gauge slowly returns to normal operating temperature. Drive a few more miles, overheats. Stop, turn off car, wait a couple minutes, same story.I continue driving fifteen miles straight home and it doesn't overheat at all, even in stop and go traffic.

Shop says head gasket, yet there is no oil in the coolant or vice versa. No white smoke from tailpipe. Spark plugs didn't show signs of overheating. Coolant doesn't smell like gas, however it did smell like a rotten fish had been in the radiator.

Is the shop trying to get me to pay them to do a headgasket I don't need? Anything else I can do to confirm the head gasket is or isn't the issue?

Any/all help is appreciated. :)

[tabasco122]

have you replaced the water pump? is the belt tight?

[LUCKYxS13]

Usually, if the HG is good, i would say there is still air in the system or the thermostat was installed upside down. Also how was the system bled?? Your supposed to jack up the front of the car 3-4in, turn the car on and turn the heat all way up. Then take rad cap off, put a funnel in and pour coolant and bubbles should come out.

[squatting pigeon]

any water on the spark plugs?

[future]

How's your timing?

And also there is things you can buy to test the coolant for exhaust gases. That's your best bet

[grandma's koukis]

Should've mentioned I had the shop confirm the water pump was fine when doing all this, also they were the ones who bled the system so I can only assume they did it propery.

They have worked on hundreds of 240's which is why I figure they bled it properly, however I guess it's something that can be rushed as well...


Edit: shop did the thermo as well, so I'm guessing that's in there properly. I have no way of checking the timing myself but it pulls exactly as hard as my friend's 97, we're both bone stock and completely neck and neck.

[ca18_luv]

Check your thermostat. Could be upside down as stated or if its a crappy one it could be getting stuck open or close depending on the scenario.

[S14Lee]

Check your radiator to make sure you have enough coolant and check for broken hoses heater core and so on

[grandma's koukis]

If thermo was bad I don't think I would've been able to drive 15 miles freeway + stop and go traffic with out it overheating, ya know? Radiator hoses are brand new, coolant hoses held 20 psi for half an hour so they're good (connections are secure)

Shoudl've also mention the car has the heater core bypassed.

[trainkiller]

My car use to overheat but my issue was a bad rad cap.

just throwing another idea out there

[grandma's koukis]

I should also throw in that it isn't boiling into the overflow tank or steaming from the cap. The needle just shoots up and my ecu instantly tries to compensate, obviously making the car run like sh!t.

It just seems odd to me that it would overheat twice then be completely fine with no fluctuations at all. I ran the car hard as hell trying to get it to do it again and it was still at normal temps according to the gauge. I haven't driven it since said night

[LUCKYxS13]

If its not going into the overflow or steaming from the cap, i would check the thermo. Im guessing its installed upside down and isn't opening.

[silva.240]

I would definately bleed the system again. do it yourself. it took me like 4 trys after getting my motor installed. it was like a complete week that i had to test my car out. flush ,fill, bleed test, overheat, re-do.

[grandma's koukis]

I would definately bleed the system again. do it yourself. it took me like 4 trys after getting my motor installed. it was like a complete week that i had to test my car out. flush ,fill, bleed test, overheat, re-do.



I'm going to try this tomorrow and see what's up, then I can also check the temps on both the rad hoses to see if one is hotter than the other indicating thermostat problems.

My next step if both those check out is the chemical coolant test kit, I'll keep this thread updated but please feel free to mention if you think it could possibly be anything else.

[future]

When I swapped my motors my car didn't have engine for a month or two so the all the coolant in the heater core dried. It took me three new Nissan thermostats and two water pumps to find out that it was all cause I didn't bleed t right everytime. There was alot of air in the heater core and that was my problem. It would overheat, run good, then start to overheat when I would drive it the next time just like with you.

[Mishkin_707]

Well before you start tearing stuff apart, check your coolant temp sensor, the two pin that's the one that send signal to your ecu, single pin is tue one that gets signal to the gauge cluster, make sure there is no corrosion in the connector and make sure it's plugged in all the way.

[idahotuner]

do you have an after market water temp gauge? you cant rely on the stock on

[Tempo]

I had the same problems with my car when i purchased it last year , we changed the radiator/thermo/temp sensor/flushed it 5 times/new cap, it happend to be because the HG blew , but i didn't notice anything mixed into the coolant or in the oil for a while , so drove on turning my car off while coasting ever so often, until it got worse then shit started mixing , next thing im pouring a whole jug of coolant into my radiator everyday before i drove , swapped the engine for a lower mileage KADE and everything ran perfect, when i drove it off after the swap it over heated again, WTF?? :wtf: so i check and it was because the guy who put the engine in didn't tighten the belt so my water pump wasn't fully working, so i went back and had him tighten it and ever since car has been running strong :bigok:

long story short it could be a blown head gasket, loose belt , bad thermostat(even if its new, i replaced mine and tested the old(new one) and it was faulty), or it could be that there are air pockets in your radiator, theres a bolt at the top radiator hose near the head you have to unscrew when you fill up with coolant so that it lets all the air out.

take my story as a suggestion though, it could maybe be something else :bow: