Honda Motorcycles - FireBlades.org banner

1 - 7 of 7 Posts

·
Registered
Joined
·
14 Posts
Discussion Starter #1
1999 F4, original owner, last model year with carbs, have done extensive upgrades to it over the years, it's a track bike and daily driver. Heads are milled .020", 1.7 jet kit, full micron system, racetech suspension... yada yada... I do all my own work, but this has me stumped....

Lately I've had an issue with overheating. +240 degrees at idle. Moving tends to cool it down enough, but you can feel heat dumping off the fairings as you move.

I dumped the coolant and it appears that there is a sludgy oil residue mixed in with it. So I'm thinking head gasket. A leakdown test showed that 5% on #1, and 3% on the rest. No bubbling in the radiator while testing. Just air noise in the crank/oil fill spout (normal).

Ran bike with a cooling system pressure gauge on the radiator. Pressure slowly went up to 16 psi where it's supposed to be... then continued to rise as the bike warmed up, up to 28 psi then I shut it down for fear of damage to the cooling system internals.

So I think it 'could' be a headgasket as something is pressurizing the cooling system. Pulled the heads, no obvious signs of a break thru in the gasket or burns where combustion blew by... Gasket looks normal for all intensive purposes.

I'm thinking now that the oil inter cooler has a break thru leak that is allowing high pressure oil into the cooling system.

Is this a problem that anyone has seen before? Before I go and buy another cooler? Any testing ideas on the old one?

FYI, I don't see any coolant in the oil after draining it, no white milkiness.....

Thanks
Vince
 

·
Super Moderator
Joined
·
32,034 Posts
1999 F4, original owner, last model year with carbs, have done extensive upgrades to it over the years, it's a track bike and daily driver. Heads are milled .020", 1.7 jet kit, full micron system, racetech suspension... yada yada... I do all my own work, but this has me stumped....

Lately I've had an issue with overheating. +240 degrees at idle. Moving tends to cool it down enough, but you can feel heat dumping off the fairings as you move.

I dumped the coolant and it appears that there is a sludgy oil residue mixed in with it. So I'm thinking head gasket. A leakdown test showed that 5% on #1, and 3% on the rest. No bubbling in the radiator while testing. Just air noise in the crank/oil fill spout (normal).

Ran bike with a cooling system pressure gauge on the radiator. Pressure slowly went up to 16 psi where it's supposed to be... then continued to rise as the bike warmed up, up to 28 psi then I shut it down for fear of damage to the cooling system internals.

So I think it 'could' be a headgasket as something is pressurizing the cooling system. Pulled the heads, no obvious signs of a break thru in the gasket or burns where combustion blew by... Gasket looks normal for all intensive purposes.

I'm thinking now that the oil inter cooler has a break thru leak that is allowing high pressure oil into the cooling system.

Is this a problem that anyone has seen before? Before I go and buy another cooler? Any testing ideas on the old one?

FYI, I don't see any coolant in the oil after draining it, no white milkiness.....

Thanks
Vince

Was it actually using any coolant?
Did you try connecting the oil cooler lines together to bypass the cooler?
If the pressure went that high without blowing the relief valve then you have a problem with the radiator cap.
If the cap is jammed shut then the pressure is obviously going to go much higher, until it blows a hose.
Heat is pressurising the cooling system as it should but the relief valve should pop to relieve the pressure.
 

·
Registered
Joined
·
14 Posts
Discussion Starter #3
I had the rad cap off during the test, as the pressure tester attached to the radiator neck. The bike never overflowed or consumed coolant, but occasionally I did smell coolant burning. Yes there could be a problem with the rad cap too... but that was out of the equation when the tester was installed.

I let the coolant stratify overnight in a clear container and there is an oil sludge layer on top, just the the damn gulf of mexico was after the drilling disaster.

It's not so much question of IF oil is in the coolant, but where the heck is it coming from.

I didn't by pass the oil cooler, that would have been too easy, doh... bike is already in pieces at this point. I removed the oil cooler and I did hook a leakdown tester do the coolant inlet side of the oil cooler (capping off the other outlet) and pressurized the cooler's water lines to 80 psi, it held and showed no leakdown, and no bubbles could be seen when the part was submerged in water... But this honestly doesn't tell me jack about if high pressure oil is being forced the other way via the cooler, I have no way of testing that now though.

Besides the head gasket, are there any other passages where oil can find its way into the cooling system? :idunno:
 

·
Super Moderator
Joined
·
32,034 Posts
I had the rad cap off during the test, as the pressure tester attached to the radiator neck. The bike never overflowed or consumed coolant, but occasionally I did smell coolant burning. Yes there could be a problem with the rad cap too... but that was out of the equation when the tester was installed.

I let the coolant stratify overnight in a clear container and there is an oil sludge layer on top, just the the damn gulf of mexico was after the drilling disaster.

It's not so much question of IF oil is in the coolant, but where the heck is it coming from.

I didn't by pass the oil cooler, that would have been too easy, doh... bike is already in pieces at this point. I removed the oil cooler and I did hook a leakdown tester do the coolant inlet side of the oil cooler (capping off the other outlet) and pressurized the cooler's water lines to 80 psi, it held and showed no leakdown, and no bubbles could be seen when the part was submerged in water... But this honestly doesn't tell me jack about if high pressure oil is being forced the other way via the cooler, I have no way of testing that now though.

Besides the head gasket, are there any other passages where oil can find its way into the cooling system? :idunno:

If you had the pressure tester attached to the radiator neck than obviously the pressure was going to keep rising until something blew. The important thing is, when you pressurised the system did it retain pressure or was it leaking somewhere?
I would have flushed out the cooling system, refilled it and kept an eye on it to see if it was getting oily again. The other obvious place for potential oil ingress would be at the pump itself.
Was it actually using any oil or coolant?
Having oil in the coolant would of course reduce the effectiveness of the coolant which might explain the cooling problem you mentioned. I'm assuming the fan was working correctly?
 

·
Registered
Joined
·
14 Posts
Discussion Starter #5
If you had the pressure tester attached to the radiator neck than obviously the pressure was going to keep rising until something blew. The important thing is, when you pressurised the system did it retain pressure or was it leaking somewhere?
I would have flushed out the cooling system, refilled it and kept an eye on it to see if it was getting oily again. The other obvious place for potential oil ingress would be at the pump itself.
Was it actually using any oil or coolant?
Having oil in the coolant would of course reduce the effectiveness of the coolant which might explain the cooling problem you mentioned. I'm assuming the fan was working correctly?
We pressurized the system and it held 20 psi while cold, for about 10 minutes. There was an imperceptible drop on the needle, maybe .05 psi.... hard to tell.. I should have pressurized it overnight and checked the drop then... oh well.

It's hard for me to think there is oil ingress at the back of the pump. The crankcase is at a lower pressure than the inside of the pump. Unless someone has experience with the pump picking up oil from its backside (the drive shaft input side)?

Why would the pressure keep rising with the tester on top of the rad? We hot purged the rad a little bit (burped it by hitting the tester's relief knob)...dropped the pressure and restarted, it then continued to climb, slowly, all the way to 30 psi where we shut it down... When we started the test it got to 10 psi really slowely, then rapidly picked up speed up to 30 psi when the thermostat opened and the whole cooling system was in line.

Strange that the overflow can was never overflowing when the bike was driven on the street... that tells me it's not fluid expansion but maybe air bubbles being injected from the head gasket (if it was leaking)...

Yes the fan works properly and kicks on about 210 give or take...

As far as I can tell it was not using oil or coolant at all.
 

·
Super Moderator
Joined
·
32,034 Posts
We pressurized the system and it held 20 psi while cold, for about 10 minutes. There was an imperceptible drop on the needle, maybe .05 psi.... hard to tell.. I should have pressurized it overnight and checked the drop then... oh well.

It's hard for me to think there is oil ingress at the back of the pump. The crankcase is at a lower pressure than the inside of the pump. Unless someone has experience with the pump picking up oil from its backside (the drive shaft input side)?

Why would the pressure keep rising with the tester on top of the rad? We hot purged the rad a little bit (burped it by hitting the tester's relief knob)...dropped the pressure and restarted, it then continued to climb, slowly, all the way to 30 psi where we shut it down... When we started the test it got to 10 psi really slowely, then rapidly picked up speed up to 30 psi when the thermostat opened and the whole cooling system was in line.

Strange that the overflow can was never overflowing when the bike was driven on the street... that tells me it's not fluid expansion but maybe air bubbles being injected from the head gasket (if it was leaking)...

Yes the fan works properly and kicks on about 210 give or take...

As far as I can tell it was not using oil or coolant at all.
If the system held 20psi then I'd be surprised if it has any leakage into an oil gallery or gasket.
The pump is sucking so if there's a leak it will suck oil through from the crankcase. But such a leak should've showed up when you did the leakdown test on the cooling system.
Because the pressure increases with coolant temperature. If you warmed the engine up to operating temp first and then installed the gauge you shouldn't have seen any significant increase unless the temperature rose further. Since the thermostat was not open clearly the engine was not up to temp when you tested it. As the temp rose you would expect the pressure to rise - that's how the system works.
I can't see anything to indicate any leakage in the cooling system at all. The oil you saw could've come from anywhere. Maybe the radiator or pump was bought secondhand from a bike that did blow a head gasket and it was never properly flushed?
 

·
Registered
Joined
·
14 Posts
Discussion Starter #7
If the system held 20psi then I'd be surprised if it has any leakage into an oil gallery or gasket.
The pump is sucking so if there's a leak it will suck oil through from the crankcase. But such a leak should've showed up when you did the leakdown test on the cooling system.
Because the pressure increases with coolant temperature. If you warmed the engine up to operating temp first and then installed the gauge you shouldn't have seen any significant increase unless the temperature rose further. Since the thermostat was not open clearly the engine was not up to temp when you tested it. As the temp rose you would expect the pressure to rise - that's how the system works.
I can't see anything to indicate any leakage in the cooling system at all. The oil you saw could've come from anywhere. Maybe the radiator or pump was bought secondhand from a bike that did blow a head gasket and it was never properly flushed?
As far as I know, it's the original pump. Any way to test the shaft seals to make sure oil is not intruding that way?

When we did the hot pressure test we absolutely waited till the tstat opened, I measured 210 degrees with an IR thermo at the rad hose inlet port and we could feel fluid flowing thru the hose. Plus the fan was cycling on and off while idling. At this point is when the pressure started to rise on the tester at a dramatically faster rate....

My initial diag was a leaking head gasket or oil cooler, that only broke thru at very high temps and under running conditions?

Thanks for keeping the ideas flowing.
 
1 - 7 of 7 Posts
Top