Over heating at idle...still...not much left to replace...

[ali954]

I got this cb7 for free when timming jumped and valves were bent. reused the head gasket with copper spray, replaced bent valves with valves off a junk head, new valve seals, relapped valves, put head on. Runs fine no smoke no coolant in oil and vice versa. no smoke anywere. no leaks.

It over heats at lights and cools down if i rev while waiting and as soon as i go.
Replaced a couple hoses that sprung leaks. I don't see any other coolant leaking.
Replaced the thermostat. a 190 deg came out and i put in an OE spec 180 deg, both of which i tested and it seamed like the new one opened up easier and more than the old.
Right now I have the heater core bypassed, as in a new line from water pump pipe to side of the head. Thought the heater core was leaking but found out that was from the ac.
fans come on and off normally, although i think when its over heating the fans will still cycle.
also flushed radiator and ran water through it and it flows fine.
what's left? doubt its the water pump, i dont understand if those can even go bad.
also tried to bled the system, left the rad cap off and t-stat valve open and let it run for a while and the fans cycled on and off numerous time. Then close the valve and put the cap on. Though it was good until it started to over heat again later on. im a delivery driver...

[ChIoVnIdCa]

Water pump go bad and leak out the weepage port.

You reused a head gasket???????

[ali954]

as i said i cant see any leaks. although i got it home today and the water was low. although when it over heated the over flow was full and i dumped some out.

and yes i reused my head gasket, got the car for free and trying to invest as little money as possible.

[leftouch]

over heating at idle and a steady decline in temp as you drive is a classic symptom of a dead water pump (e.g. spun impeller).

[drewams]

Water pump go bad and leak out the weepage port.

You reused a head gasket???????

Definitely sounds like it could be the water pump. What is a weepage port????

[93Accordian]

Definitely sounds like it could be the water pump. What is a weepage port????

It's a little hole in the bottom of the water pump that will drip or dribble if the pump goes bad. It may not be the most noticable drip, but if there's any water coming out of it at all, get a new pump.

[93Accordian]

It over heats at lights and cools down if i rev while waiting and as soon as i go

The 3 most common issues with the symptoms you listed are a bad water pump, air in the system, or fans not properly kicking on. I'm going to go with the water pump. If the pump is bad or weak, it won't circulate properly at low rpms, such as idle. Once you start moving, the pump spins enough to circulate some water, allowing it to reach the radiator and cool the water, instead of "puddling" in the engine and getting hot.

[drewams]

It's a little hole in the bottom of the water pump that will drip or dribble if the pump goes bad. It may not be the most noticable drip, but if there's any water coming out of it at all, get a new pump.

Was not aware of that. Interesting. I am looking at doing a total overhaul on my CB. Probably one of the first things I need to look at is timing and water pump. Thanks.

[93Accordian]

Was not aware of that. Interesting. I am looking at doing a total overhaul on my CB. Probably one of the first things I need to look at is timing and water pump. Thanks.

They are both an excellent place to start and are both cheap.

[quickangel93]

if i were you id invest in a headgasket and waterpump. never ever reuse a headgasket

[ali954]

was hoping not to replace the water pump but i guess thats my next option. goin to get new belts and tensioners while im there.

over heating at idle and a steady decline in temp as you drive is a classic symptom of a dead water pump (e.g. spun impeller).

whats a spun impeller? if the water pump was bad would i be able to see a leak on the back of the engine?

[93Accordian]

was hoping not to replace the water pump but i guess thats my next option. goin to get new belts and tensioners while im there.


whats a spun impeller? if the water pump was bad would i be able to see a leak on the back of the engine?

You'd see it drip from the weep hole on the bottom of the water pump.

[Fleetw00d]

Exact same symptoms on my 93 EX last fall. Leaking head gasket was allowing compressed air into the cooling system. I could actually see bubbles in my overflow tank. No oil in the water, no water in the oil. If you're going to go the trouble of removing a head, it only makes sense to use a new gasket, now you're going to have to do it again.

[batever]

Exact same symptoms on my 93 EX last fall. Leaking head gasket was allowing compressed air into the cooling system. I could actually see bubbles in my overflow tank. No oil in the water, no water in the oil. If you're going to go the trouble of removing a head, it only makes sense to use a new gasket, now you're going to have to do it again.

BUT it's not clear if the engine is actually overheating or whether he's just getting a high temperature reading off the coolant temperature sensor--if he's getting that, it would tend to indicate that there isn't or might not be air in the cooling system (because that tends to lower the temperature sensor reading).

If there is air in the system, it might affect the thermostat opening point. So switching to the 180F t stat would be a move in the correct direction (a kludge, but a good kludge). a 170F one might be even better in this case if it were available.


Things that poin to the water pump, is that the temperature goes down when you increase the revs of the engine, thus increasing the volume of fluid pumped per second by the water pump.

Check that weep hole in the pump.

could be the head gasket, as pointed out, but the description the OP gives would make me suspect the water pump first--while still looking hard at the head gasket, of course.

If i were going to reuse a head gasket I would find a way to uniformly heat it up to proper annealing temperature for aluminum (they are aluminum, right) to resoften it/remove the work hardening first. Around 700F. then let it cool.


Although this:

"also tried to bled the system, left the rad cap off and t-stat valve open and let it run for a while and the fans cycled on and off numerous time. Then close the valve and put the cap on. {but it overheated again later}"

<<<<this points to the possibility of new air getting introduced to the system after you bled it....which is consistent with certain kinds of head gasket leakage.


without a doubt, this is my least decisive post ever. Good luck, OP.

[accordztech]

If i were going to reuse a head gasket I would find a way to uniformly heat it up to proper annealing temperature for aluminum (they are aluminum, right) to resoften it/remove the work hardening first. Around 700F. then let it cool.

.

Never never never never reuse a head gasket. Only if its MLS. But why do a few hours worth of work, and not change the headgasket?

You will have to many varibles in the future if you have issues with overheating. If your going to reuse a headgasket, might as well reuse your oil.