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Coolant Fuckery

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Paulf
Nova Slayer



Joined: 24 Jan 2017
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PostPosted: 18:09 - 25 Oct 2017    Post subject: Reply with quote
Cb1 rocket yes recently rebuilt had a new crankshaft barrel and piston about 600 miles ago. I have a head gasket. I probably forgot to check the head bolts after 50 miles as usually recommended. We learn and 05 pantheon.
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Past bikes simsom mofa 1s, suzuki hustler 250 (£35 in 1973), suzuki ts125k, mz150, yamaha yb 100, honda pc50, honda vision 50, all 2 stroke - then cars - honda pcx 125 (sold) own honda fes 125 and Mrs 125 spares or repairs. Started 1972 all accidents walked away no insurAnce claims
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cb1rocket
World Chat Champion



Joined: 30 Jan 2010
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PostPosted: 23:24 - 25 Oct 2017    Post subject: Reply with quote
Feel a bit bad hi jacking this thread so start a new thread if still on going. Where did you get the parts from and where did the headgasket come from? I have had 3 of them failed and they were all rebuilt. Pm me if so
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Falco
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Joined: 27 Nov 2015
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PostPosted: 19:21 - 27 Oct 2017    Post subject: Reply with quote
(Minor) Update: The "Blown Head gasket" kit finally came. Ran the bike up to temp and tested it. No colour change, reservoir filled quickly and temperature gauge went up to half way pretty fast. The radiator hoses don't go solid at any revs up to 10K.

Is head gasket still the most likely cause of the problems?
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cb1rocket
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Joined: 30 Jan 2010
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PostPosted: 20:05 - 27 Oct 2017    Post subject: Reply with quote
Sounds like it doing what it should be doing
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P.
Red Rocket



Joined: 14 Feb 2008
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PostPosted: 21:03 - 27 Oct 2017    Post subject: Reply with quote
cb1rocket wrote:
Sounds like it doing what it should be doing


Umm...
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Robby
Dirty Old Man



Joined: 16 May 2002
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PostPosted: 12:35 - 28 Oct 2017    Post subject: Reply with quote
You mentioned several posts back that there is no rad cap.

Just to be sure, there should be a pressure cap (usually called a rad cap) and a soft cap on the expansion vessel. You need to fill it up at the pressure cap. If the coolant is low and you fill up the expansion vessel, you'll just end up squirting coolant out of the expansion vessel when the bike warms up - but hopefully sucking more back in when it cools down.

Whilst a head gasket is a possibility, I would want to check everything else first. A head gasket on that bike isn't necessarily difficult, but it does give you several ways of really screwing the engine if you cock up the procedure.

Things I would do before pulling the engine apart:
1. Make sure the rad is clean externally, nothing blocking the fins.
2. Flush through the cooling system (rad and block) with a garden hose.
3. Check the thermostat. Put in a pan of water with a thermometer, head the water, see where the stat opens. Usually around 75-80 celcius.
4. Replace the pressure cap.
5. Refill with fresh coolant. Bleed properly (usually running the bike up to temp with the pressure cap off. The coolant level will drop when the thermostat opens.)

I would be doing all of this if I was replacing a head gasket anyway, because it's really annoying when you replace a head gasket and then blow the new one within 50 miles because the thermostat was dodgy.
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Falco
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Joined: 27 Nov 2015
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PostPosted: 13:59 - 28 Oct 2017    Post subject: Reply with quote
Robby wrote:
You mentioned several posts back that there is no rad cap.

Just to be sure, there should be a pressure cap (usually called a rad cap) and a soft cap on the expansion vessel. You need to fill it up at the pressure cap. If the coolant is low and you fill up the expansion vessel, you'll just end up squirting coolant out of the expansion vessel when the bike warms up - but hopefully sucking more back in when it cools down.

Whilst a head gasket is a possibility, I would want to check everything else first. A head gasket on that bike isn't necessarily difficult, but it does give you several ways of really screwing the engine if you cock up the procedure.

Things I would do before pulling the engine apart:
1. Make sure the rad is clean externally, nothing blocking the fins.
2. Flush through the cooling system (rad and block) with a garden hose.
3. Check the thermostat. Put in a pan of water with a thermometer, head the water, see where the stat opens. Usually around 75-80 celcius.
4. Replace the pressure cap.
5. Refill with fresh coolant. Bleed properly (usually running the bike up to temp with the pressure cap off. The coolant level will drop when the thermostat opens.)

I would be doing all of this if I was replacing a head gasket anyway, because it's really annoying when you replace a head gasket and then blow the new one within 50 miles because the thermostat was dodgy.


Sorry, that was a bit of miscommunication on my part. I've seen bikes with caps for filling coolant directly on the radiator so I assumed that was what was meant by a radiator cap. The cap I am referring to is the pressure cap under the tank.

1) Fins look fine, but even if they weren't it doesn't explain why the system isn't refilling when it cools down (when opened last time there was no coolant at the pressure cap and even the thermostat housing was empty.
2)I'll do this since the system has to be drained for the gasket change any way, but as above I don't see how it matches the symptoms.
3)Checked it as part of initial fault finding, works fine.
4)Is there a way to test this beyond simple replacement?
5)Done during the inital fault finding. Topped it up after bleeding, took it on test run, had to remove the same amount of coolant I had added as the expansion vessel was brimming over.

In essence, when it heats up it pushes the coolant into the vessel but overheats and won't pull the coolant back into the system when it cools.

Cheers for the help!
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Robby
Dirty Old Man



Joined: 16 May 2002
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PostPosted: 15:38 - 28 Oct 2017    Post subject: Reply with quote
A dodgy rad cap could cause those problems, seeing as it's job is regulated pressure (a bit) and the flow of coolant to and from the expansion vessel.

I don't know of a test for them, and they don't tend to be that expensive, so I would just replace it and see if the problem goes away.
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Falco
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Joined: 27 Nov 2015
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PostPosted: 22:35 - 28 Oct 2017    Post subject: Reply with quote
Robby wrote:
A dodgy rad cap could cause those problems, seeing as it's job is regulated pressure (a bit) and the flow of coolant to and from the expansion vessel.

I don't know of a test for them, and they don't tend to be that expensive, so I would just replace it and see if the problem goes away.


Cheers again Robby Thumbs Up

Should be here the middle of next week. I'm replacing the head gasket anyway since I had to take off the carbs and exhaust any way, rather than put them back on and take them off again if it's not the radiator cap.
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Falco
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Joined: 27 Nov 2015
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PostPosted: 20:50 - 06 Nov 2017    Post subject: Reply with quote
Final update: Replaced head gasket and radiator cap, after tracking down the 2 clamps I inevitable forgot to nip back up I took it for a spin for about an 1 hour tonight. Cold Night but the temp gauge was solidly at the bottom of the scale even through town. Hopefully it'll behave on the commute tomorrow as I won't be held responsible for my actions if I have to get up at 5.30 to get on the god-damn train.
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Old Thread Alert!

The last post was made 6 years, 166 days ago. Instead of replying here, would creating a new thread be more useful?
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