Gentlemen here are the basics

91 Civic DX
90 D16A6 Motor
Some bolt ons, nothing else

I have searched, and I think I know what to start with, but looking for anyone who has had and solved this issue.

I Drove this car 18 hours from BC to Cali with no issue. Today while doing some mountain runs with friends my car over heated on a very steep incline. Stopped the car, and could hear hissing. I thought it was the rad, but opening the hood I see its actually coming from the overfill reservoir. The hose in the reservoir is blowing our steam. We waited, the opened the cap on the rad to find that it was a least a liter down. Put some water in and continued driving. Going up steep hills and then later on the hiway, if I bring the RPMs up and have my foot down, the temp needle begins to climb. As soon as I get off the gas the needle drops immediately. Did this for the rest of the day. Upper Rad hose is hot, lower rad hose is warm. Needle was not climbing under normal acceleration and normal driving.

I was going to start with the rad cap and thermostat, but does anyone else have any suggestions? If it was the water pump I would think it would be over heating all the time, not just at full throttle.

Any constructive suggestions would help.

 

Sounds to me like you have a blown head gasket. The air is escaping the combustion chambers and getting into the water jackets. This displaces the coolant out the overflow. Same thing just happened to my D series... pull the head and replace with a Y8 metal headgasket.

 

Wow, I was really hoping to not hear that, although I had my suspisions.

I am going to change the thermostat first, and then move on to the head gasket. Im hoping its the thermostat, but I think your right.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ZCcivic91 &raquo;</TD></TR><TR><TD CLASS="quote">I am going to change the thermostat first, and then move on to the head gasket. Im hoping its the thermostat, but I think your right. </TD></TR></TABLE>

Yeah... it's always a good idea to check the little things out first. Once you rule those out, move on to the big stuff.

 

Changed the thermostat today. Its not over heating, the needle dosent budge. But its still overflowing the overfill tank and boiling the water in it. I am going to change the rad cap ( a long shot I know) to see what happens. After that its water pump, and then I dont know.

I dont think its the head gasket becouse if it was, I would be seeing coolant in the oil, and oil in the coolant, and Im not. Hopefully its just a rad cap, we will see.I cant go on anymore mountian runs until I figure it out

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ZCcivic91 &raquo;</TD></TR><TR><TD CLASS="quote">I dont think its the head gasket becouse if it was, I would be seeing coolant in the oil, and oil in the coolant, and Im not. Hopefully its just a rad cap, we will see.I cant go on anymore mountian runs until I figure it out </TD></TR></TABLE>

Not necessarily... I didn't when mine blew. If it's just air getting into the waterjackets, it will displace the coolant. Those are air bubbles you're seeing in the overflow.

 

Well I just replaced my rad cap, and went for a drive, then parked and held 4k RPM for a while. No bubbling from the over fill tank.

Hopefully I ve got this solved. We will see tommorow when I can drive it more but it may have been that easy.

The rad cap seal may have been allowing the water to boil close to the top of the rad. The steam was pushing into the overflow tank and boiling the water there. Hopefully this is solved!

 

I hope you're right for your sake. The best test would be a highway test (or mountain road test) maintain 120km/h then park and check the overflow.