85 XJ 700 overheat Problem

I have a 85 XJ 700 that overheats. Starts n runs fine and doesn't use any oil. After motor warms up it goes straight to Hot and starts spewing anti-freeze from overflow jug. I drained all old anti-freeze out and put new anti-freeze in but still does the same thing. Please help I drive my bike a lot to save fuel and the Tahoe is killing my wallet.

 

I would suspect a thermostat but you need to tell us a little bit more.

Are you riding when it spikes to HOT or just idling?
Does the fan come on?

What condition was the coolant when you drained it? (was it all nasty or did it look OK)...did you flush the radiator when you drained the coolant?
Is the radiator getting HOT too? There is an inlet and outlet to the radiator. The side that connects to the water pump (above the clutch cover) is the cold side. When it's spewing, is that tube hot too? If not really hot, then the rad isn't getting any flow.

The radiator may also be plugged. I rigged up an adapter and hooked it to a garden hose with good flow and pumped a bunch of water through the rad, then drained it, then put in some of that radiator flush and left it soak, then flushed again with the garden hose.

 

I am riding the bike when it starts spewing. The fan does come on and when I drained the fluid was like milky brown.

 

Most likely the thermostat but if your old coolant was dirty i would flush the whole system also.

 

milky brown is not good sounds like might have a bad head gsk. Combustion is pressurizing the cooling system. easy way to check the t-stat let it warm up see if the hose gets hot as well as the radiator. If you go past a local radiator shop have them do a sniffer test it detects exhaust in the radiator. Hopefully its the thermostat. Sometimes the head gets a crack between valves not enough to flow water in the combustion chamber but air can flow out as it warms up the crack opens up

 

Thanks for the advice. I flushed the rad today and ordered a thermostat. I'll post next week when it comes in and let everyone know the outcome.

 

Wow...you should really do a little checking before you run out and buy parts.
The thermostat is pretty cheap, so no biggy but you can easily test it.

Just drop it into some hot water and heat the water until it boils. The stat should open around 190 deg IIRC (before the water boils) and it should open all the way.

It's a bit of a pain to get out so it's a good idea to have the new one waiting when you pull the old.
Did you get the gasket...or is it a square O-ring seal (can't remember)

The brownish coolant is a bad sign and you may very well have a cracked head or bad head gasket but the stat is a cheap and quick check. No guarantees!

 

If oil is getting in your coolant, then coolant is probably getting in your oil too. Start the bike and let it idle up to temp, then hold your hand or rag behind the exhaust, you can sometimes smell the coolant coming out from the pipe. Also, what does your oil look like? If the view window has turned a milky colour then that will indicate that coolant is getting in the oil as well.
Hope it's a minor fix for cheap dollars, if it's the head gasket or a cracked head, please accept my sympathies.

 

Well thermostat didn't work. Kinda figured it was the head. Anyone know where I can get a good used motor at? Or will a XJ 750 motor fit my bike. Or even if a XJ 750 head will fit my 700 motor?

 

you can only use the x head. PM designer mike if i recall he had xtra parts. It might just be a bad head gasket but you wont know till you pull it. I see heads on ebay but you don't know how they are. I have also seen lo mile motors going for under $500 but you have shipping some of them even have videos of the bike running. I am not sure if the airhead motor bolts up the same. I was hoping it was the thermostat

 

I'm sure I have a head.

No other head will fit it except an X (20 valve) head
It would be a major PIA to swap to a different flavor of engine.

Pull the head and see. You have a decent chance it's just a head gasket yet.

Did you flush the radiator with major flow from a garden hose? I'd hate for you to pull the head when it's just a plugged up radiator.

Pulling the head is not a 10 minute job and the head gasket is something like $65 alone

 

How much for a used head Mike?

 

could something gone wrong with the water pump or gear. I dont think so but still easier to check then pulling the head i have no clue on the water pump on these Knock on wood mine is ok right now

 

Could take the rad to a rad shop see how much it'd cost to hot tank and flow check it. I took mine off one time because of overheating and you should have seen the crud that came out (poor maintenance by me). That was just using something attached to the rad and hooked up to a garden hose in reverse flow, watch that you don't go full blast, even with a garden hose.

 

I don't believe thats the problem it started all at once i believe. That could have been what caused it but its hard to tell. I am sure the guy is pretty bummed about now. Would be nice if it was something simple. If he only knew someone with a repair shop or radiator shop it only takes a few min to do a sniffer test the would tell for sure weather the head or gsk is the problem. How many miles are on the bike ?

 

It has a little over 32,000 on it. When I flushed the rad it was pretty clear and good flow. It did happen all of a sudden. Just got off highway when it happened. Ran good down the highway.

 

Schell.... mind adding your bike and info to your signature? Thanks!

 

It has a little over 32,000 on it. When I flushed the rad it was pretty clear and good flow. It did happen all of a sudden. Just got off highway when it happened. Ran good down the highway.

 

Bike has a little over 34,000 on it. It did happen all of a sudden. I was coming down the interstate and bike was running good. Got off the interstate and just started spewing the fluid. Is there a way to check the water pump?

 

The water pump is dead simple and extremely reliable.
That being said, there have been a couple guys with pump drive issues.

Hmmm> How long you had the bike and where are you from? Maybe you inherited one of them!

Here is a little slide-show I put together when trying to help another guy a couple years ago.
http://s288.photobucket.com/albums/ll16 ... ce3311.pbw

The plastic gear is on the water pump shaft. The metal gear is on the same shaft as the alternator so it's almost guaranteed to be spinning.
Pop the cover off and take a look inside. One bike was missing the collar which allowed the gear to float around and not engage the water pump gear. Also, notice there is a big flat washer under the gear, it holds the bearing in place. That NEEDS to be there otherwise the entire shaft can float in and out and again potentially strip the gear.
IF the radiator gets warm once the bike gets to operating temp. (both hoses get warm) then the pump is circulating water and probably not your problem.
As cutlass noted, a sniffer is the easiest way to nail it down to the head/or gasket.