93 cx d15b coolant goes to overflow but doesn’t return when cold and the fan won’t turn on. I’ve replaced radiator, temp sensor, coolant switch and thermostat. I’ve jumped the fans from the switch and they turn on. Any help is appreciated

 

Get the radiator as full as you can. Start the engine (cold) with the radiator cap off and rev it. If bubbles or coolant blow out of the radiator, there's a leak in the engine, usually the head gasket.

 

The coolant continuously rises up until it’s at operating temp n I’ve let it sit for like 30 minutes with the cap off filling it and revving it,some bubbles came out. the fan never come on. Took it for a drive real quick, came back and had coolant in res and let it cool and it did not suck it back up


the only reasons I can see the fans not turning on are a) because I bought a faulty coolant fan switch from autozone ( because I tested the circuit by jumping it at the fan switch and it worked) or b) the headgasket is blown and is somehow making the fan not turn on.

 

Coolant not being drawn back in is a faulty or incorrect radiator cap. You need the 1 bar (16 psi) radiator cap. You can test your cooling system and the radiator cap with a rad pressure tester. If there is a leak, it will tell confirm.

 

The one I have says 1.1 on the cap

 

Did you bleed the cooling system properly, which includes purging air by loosening the bleed bolt?






.

 

I’m sure I bled it right but like I said the fan wouldn’t come on, I’m sure it’s not normal, I jumped it from the fan switch and it comes on but plug it in to the new sensor and nothing, no matter how long I let it sit the fan won’t come on. The coolant only seems to go to the red if I drive it, if I fill the radiator n let it sit it won’t overflow or overheat.

 

Answer to this^?

Read the diagram carefully.

 

Yes of course. Until a constant stream of coolant came from it

 

If bubbles continued to appear in the radiator through the entire bleed process, then the headgasket is blown, as mk pointed out.

You can verify by renting the block tester kit at AutoZone.

 

Yeah 1.1 is the proper psi one, the 1.6 is the one you don't want. The block tester and the rad pressure tester will tell you all the info you should be concerned with.

In hopes to clarify some from my experiences in bleeding. Without the spill proof funnel kit, the radiator will continually spit out very tiny bubbles each cycle when the fan kicks on with the rad cap off. The reason being the coolant level always drops below the lower neck line as the thermostat is wide open and coolant flow/exchange is at it's max. Then fan goes off and the coolant level rises above the lower neck but it captures a little air in the top of the rad. This tiny bit of air spits back out as a very small amount of small bubbles for a moment or two.

When your head gasket is bad, you get larger bubbles consistently regardless of fan cycles or coolant levels dropping. It's not easy to tell the difference without having experienced both. This is the benefit of the spill proof funnel kit. The coolant never goes below the lower neck line of the radiator so you can get to the point you never see bubbles of any kind. Also when the head gasket is good, when you rev the engine, coolant will rise and come out the radiator from the higher water pump output when the thermostat is closed, but it won't shoot out as mk378 mentioned. When the gasket is bad it tends to shoot out pretty strongly when you rev it. Once again, hard to distinguish without having seen it first hand on both sides.

Your best bet is to rent both the block tester and the coolant pressure tester and do both tests then report back your findings.

 

Will do, Omw to work atm. As for the fans not kicking on even without the cap on could this be because the bubbles whether the headgasket or the bleeding incorrectly trick the sensor into not turning on? Switch is new and circuit works

 

The top gasket in the radiator cap is essential for the coolant to return from the reservoir. It has to make a good seal on the top edge of the radiator neck. Also the hoses between the radiator and the bottom of the reservoir (including the elbow and the one inside the reservoir) must be airtight. The system works on the very slight vacuum that forms as the coolant contracts when the engine cools off. Any slight leak will stop it from working.

The fan switch is activated by the temperature of the coolant leaving the radiator. If there is no flow through the radiator (lack of coolant, clogged radiator, stuck thermostat, etc.) the fan may not run even though the engine does overheat. Jump the fan so it runs all the time and test drive. If there is still overheating it's not fan-related.

The head gasket check is most definitive immediately after starting the engine cold. There should be no action in the radiator when it is cold. When it warms up and the coolant starts to flow, as others noted it is hard to tell what is normal and what is not.

Another way to execute the test is to close up the radiator and feel the pressure in the top hose after you start the engine cold. There shouldn't be any until it has warmed up considerably. If you feel pressure right away after starting, that is a gas leak in the engine.

 

The only time it will overheat is if I don’t dump the coolant back into the rad for like 1-2 weeks of driving. There was no pressure after starting cold in the upper hose. The coolant will stay still until it’s about half way warmed up and then start to move around.

 

That sounds like a faulty rad cap or a leak somewhere else in the system. The coolant pressure tester lets you test both the cap and the system to isolate where it's leaking or not sealing.

 

At work right now messing with it when I can. I notice I’ll leave the cap off n start it for a minute n then the coolant starts to rise out the water neck for the rad so I’ll shut it off and close the rad and squeeze the tubes and when I open it the water level goes down. Do you think there is an air pocket in the back of the motor that is being difficult to get out? I am going to pressure test the rad as soon as I can

 

You stated with confidence earlier that the system was thoroughly bled properly. Did this include having the heater valve wide open? If so, focus elsewhere.

 

I don’t have the heater core hooked up.heater hasn’t worked since I got the car so I disconnected the heater core coolant lines. It goes from the side of the head by the temp sensor straight to the thermostat housing then out the housing and into the back of the head

 

Looped?

 

Not sure what looped means. Comes out side of head to thermos then out thermo to back of head

 

Loop from star to star.

 

Yupp star to star

 

I did just try rebleeding the system no bubbles up until the thermostat opened and I pressed the throttle a bit so I guess headgasket is blown right? As I stated it wouldn’t overflow unless I drove it. So now would this problem with the compression leaking into the coolant cause the fans to not turn on because of the air that is constantly being pushed into the cooling system