How many bubbles in radiator flow is OK?

[dcarver]

Restored a 1979 KZ1300. During the third break in ride, she overheated.

Diagnosed a dead radiator fan relay and intermittent temperature switch.

Thinking the warm/hot running might be due to a small head leak raising coolant temperature, fired her up with radiator cap off to see if the T-stat was opening and or to look for bubbles in the coolant, indicating a head gasket leak.

Here we go.. get the popcorn.

T-Stat opening

https://vimeo.com/153584344

T-Stat open... does the flow look normal? I really don't know what 'good' looks like.

https://vimeo.com/153584353

In the meantime, the radiator is at a shop getting flushed and cleaned - although it sure looked like it was flowing OK.

A new radiator cap has also been sourced.

What do you think?

Head gasket good to go?

Any tests available to determine head gasket integrity?

Just make sure the fan kicks in and ride it?

 

[Geezer]

I would expect some bubbles the first time the t-stat opens because of air trapped in the block and hoses and etc. However, eventually the bubbles should stop.

If the bubbles are actually coming from the combustion chamber ( a bad head gasket in a spot that only lets compression gas into the coolant but does not allow coolant to get to the oil) then I would expect a smell of fuel or exhaust from those bubbles. Also, I would think that the bubbles would be present even with the t-stat closed because there should be enough pressure from combustion gas to get past the closed t-stat. Otherwise, where would it go?

 

[NTXFJR]

A compression test to verify maybe?

 

[RaYzerman19]

Yep, methinks them bubbles may be a cause for concern, a few too many for my liking. Rad seemed OK to me. I would have run it some more to see if they go away (i.e., road test). I'd do a compression test, and see what that says to isolate the offending cylinder, then leakdown test (need spark plug fitting & compressed air). It is possible to have a head gasket leak without coolant in the oil or vice versa, but usually you get one or the other. Do you see any hints of an oil slick on top of the coolant? I see you got the rad out for servicing....... while you wait, drain the oil and look for coolant. You can always pour the oil back in if OK. I am assuming this oil has been in there all along..........

 

[FJRay]

Most parts stores will get you a device that tests for exhaust in the cooling system. It uses a liquid that changes color if exhaust is present. They are cheap and easy.

In some systems bubbles are caused from the rotating parts and are not a concern. You said there wasn't any sign of water in the oil and coolant in a cylinder should cause steam and the smell of coolant out the exhaust. Imho

 

[dcarver]

Yep, methinks them bubbles may be a cause for concern, a few too many for my liking. Rad seemed OK to me. I would have run it some more to see if they go away (i.e., road test). I'd do a compression test, and see what that says to isolate the offending cylinder, then leakdown test (need spark plug fitting & compressed air). It is possible to have a head gasket leak without coolant in the oil or vice versa, but usually you get one or the other. Do you see any hints of an oil slick on top of the coolant? I see you got the rad out for servicing....... while you wait, drain the oil and look for coolant. You can always pour the oil back in if OK. I am assuming this oil has been in there all along..........

The KZ1300 is notorious for trapping air in the block. The service manual... disconnect radiator fan.. boil.. add water quick. IIRC.

Can do compression test.. Have all that is needed. And leak down test too. Invested in quality stuff several years ago..

I did drain the oil and found NO signs of water contamination. And yes, this oil has been in service since new. Approx 300 miles.

The radiator, after removal, looking down the removed cap.. did see, to naked eye, a lot of debris. Radiator guy has yet to call me with results.

My .02, gut feeling, is this bike has undersized radiator for engine displacement / horsepower and without cooling fans the boiling was logical.

More to come... and THANK you for input.

 

[dcarver]

Most parts stores will get you a device that tests for exhaust in the cooling system. It uses a liquid that changes color if exhaust is present. They are cheap and easy. In some systems bubbles are caused from the rotating parts and are not a concern. You said there wasn't any sign of water in the oil and coolant in a cylinder should cause steam and the smell of coolant out the exhaust. Imho

Ray, Thank You. And the exhaust smells like exhaust. Rich exhaust. Coolant has that sweet burnt smell. KrZy8 had that.

Still, a compression / leak-down test would be good, even if to establish baseline numbers. Some day, QuackQuack will have 100k miles and it will be fun to compare a tired motor to a fresh one.

Rock On!

D

 

[DiggerDr.]

A head gasket can be bad between the combustion chamber and a coolant passage and not allow coolant into the oil. You need to verify whether or not the bubbles are caused by a leaking head gasket. FJRay had a good recommendation. On another note, after it sits overnight do you get an antifreeze smell upon startup? Or a puff of white smoke? Hoping it is just a hard to fill system. It could have gotten hot for several reasons. !. Was not completely full to begin with. Or 2. Bad head gasket. 3. Radiator or thermostat. Don't like the bubbles. Hopefully it is just hard to remove trapped air. Have not worked on one of those so I really don't know.

 

[FJRay]

Don't even talk about a head gasket. I've already put two in that engine. The after market gaskets are well known for being junk and originals are on the unobtainum list. That engine is bored out and the last time I checked there were no good quality 64mm head gaskets .

A kz1300 is one of the MOST complicated engines built to work on.

 

[DiggerDr.]

You are right, I should be shot at dawn tomorrow for just mentioning that. I too have had issues finding parts for older metric engines. I had quite the battle with Mitsubishi over diesel pistons once. I have some good connections, checking on those head gaskets. What brands have you tried? Hoping that is not the case this time. A beautiful older bike. And it sounds great!