MOTOR CHAT
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jonthefish
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Broken head?
Hoping you wise men and women can see what I cannot.
Toyota Hilux Surf 3L 1994 Jap import. Drives ok for 300 miles with coolant levels steady. Then overheats and pumps frothy coolant onto Scotland via expansion tank. So far so busted cylinder head/head gasket (usually the former on these).
From cold, the coolant starts pressurising and bubbling instantly on start up. Got to be combustion gas in coolant then. However......test for combustion gas consistently negative and no hint of white smoke at exhaust or combustion smell from rad or expansion tank. [No oil in coolant or vice versa but the way the head cracks on these this means nowt.]
Have flushed rad, block and heater matrix both ways, replaced radiator cap and thermostat, done known airlock fixes. Same bubbles and coolant loss from start up. Flushing coolant did reveal much "radweld" coppery crap in cooling system :evil: .
So.... Symptoms say cylinder head or gasket gone. Can anyone explain tester not finding combustion gas in coolimg system? It bubbles like toil and trouble so huge amounts of gas are getting in there. The gas tester definitely works for CO2 (goes blue to green if breathed on or held by exhaust). Bubbling coolant (now just water) simply smells like hot water - no hint of fumes. I'm loathe to pull the cylinder head off it just to check but cannot think what else to do.
Ideas???
cheers
EDIT- meant to put this in Motors. How to move?
Hoping you wise men and women can see what I cannot.
Toyota Hilux Surf 3L 1994 Jap import. Drives ok for 300 miles with coolant levels steady. Then overheats and pumps frothy coolant onto Scotland via expansion tank. So far so busted cylinder head/head gasket (usually the former on these).
From cold, the coolant starts pressurising and bubbling instantly on start up. Got to be combustion gas in coolant then. However......test for combustion gas consistently negative and no hint of white smoke at exhaust or combustion smell from rad or expansion tank. [No oil in coolant or vice versa but the way the head cracks on these this means nowt.]
Have flushed rad, block and heater matrix both ways, replaced radiator cap and thermostat, done known airlock fixes. Same bubbles and coolant loss from start up. Flushing coolant did reveal much "radweld" coppery crap in cooling system :evil: .
So.... Symptoms say cylinder head or gasket gone. Can anyone explain tester not finding combustion gas in coolimg system? It bubbles like toil and trouble so huge amounts of gas are getting in there. The gas tester definitely works for CO2 (goes blue to green if breathed on or held by exhaust). Bubbling coolant (now just water) simply smells like hot water - no hint of fumes. I'm loathe to pull the cylinder head off it just to check but cannot think what else to do.
Ideas???
cheers
EDIT- meant to put this in Motors. How to move?
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Have you just bought this vehicle?
Sounds like the radweld gave up holding the known problem! :evil:
I think you are on the right lines. First thing I would be doing is the sniff test, but you say it smells clean? My only thought is it's only blowing past the head gasket on the compression stroke, but then you would surely smell unburnt fuel.
I think it's gonna have to be head off anyway. :facepalm:
Sounds like the radweld gave up holding the known problem! :evil:
I think you are on the right lines. First thing I would be doing is the sniff test, but you say it smells clean? My only thought is it's only blowing past the head gasket on the compression stroke, but then you would surely smell unburnt fuel.
I think it's gonna have to be head off anyway. :facepalm:
jonthefish
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firedfromthecircus":1tyazdtn said:
Yeh - bought it a week back. Can't see I'd have any comeback so from private seller - sold as seen and all that - so hoping I can fix it, as it appears generally sound. Like you say, the head probably has to come off. I just wish I could understand why the gas tester does not pick up signs of combustion leakage - cos if the head is leaking is it doing so big-style! Puzzling.
old_coyote_pedaller
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Have you had each cylinder pressure tested? Not tested for compression but for leakage into water-jacket from head-gasket.
My mate had it done on his car years ago, used a combination of spark plug body with tyre valve Araldited into it then check each cylinder in turn to see if there's a leak.
Just had a thought that since you found Radweld crap in water, could it have blocked a waterway in head causing localised boiling hence no CO2 detected?
Have you had each cylinder pressure tested? Not tested for compression but for leakage into water-jacket from head-gasket.
My mate had it done on his car years ago, used a combination of spark plug body with tyre valve Araldited into it then check each cylinder in turn to see if there's a leak.
Just had a thought that since you found Radweld crap in water, could it have blocked a waterway in head causing localised boiling hence no CO2 detected?
jonthefish
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Thanks. I'd just been looking for a cheap pressure leak down tester. Car is a diesel and all the cheap testers are for petrol engines screwing into spark plug hole. Wonder if I could cobble together something cheap if I could find the right injector adapter?? I reckon if i could get pressure into the cylinders I'd soon know if one was leaking. We're not talking wee bubbles here so a leak will be pretty rapid and obvious I think - I'd expect to see coolant getting blown out of the radiator.
I'd also pondered localised boiling, like you suggest. But I've noticed that the gas starts bubbling from the first crank even if engine doesn't catch i.e. no heat. I still think it must be the head or gasket. Just wish I could figure out why no combustion gas being found.
Thanks. I'd just been looking for a cheap pressure leak down tester. Car is a diesel and all the cheap testers are for petrol engines screwing into spark plug hole. Wonder if I could cobble together something cheap if I could find the right injector adapter?? I reckon if i could get pressure into the cylinders I'd soon know if one was leaking. We're not talking wee bubbles here so a leak will be pretty rapid and obvious I think - I'd expect to see coolant getting blown out of the radiator.
I'd also pondered localised boiling, like you suggest. But I've noticed that the gas starts bubbling from the first crank even if engine doesn't catch i.e. no heat. I still think it must be the head or gasket. Just wish I could figure out why no combustion gas being found.
old_coyote_pedaller
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I should have realised it was a diesel. :facepalm:
So it's not localised boiling then, but as the coolant is being pressurised from cylinder, like you I don't understand why combustion gasses aren't being detected. :roll:
Don't know if all diesel injectors like spark plugs have same thread (never had the injectors out of my Passat diesel) but maybe you could get a scrap injector to make a pressuriser.
I should have realised it was a diesel. :facepalm:
So it's not localised boiling then, but as the coolant is being pressurised from cylinder, like you I don't understand why combustion gasses aren't being detected. :roll:
Don't know if all diesel injectors like spark plugs have same thread (never had the injectors out of my Passat diesel) but maybe you could get a scrap injector to make a pressuriser.
jonthefish
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:idea: I'm wondering if, since coolant bubbles just from turning over on the starter, could i do a leakage test just using the starter motor? I've never seen the inside of diesel cylinder head, but I assume that if I pop out an injector from any cylinder then there's no compression in that cylinder? If that is right, then if I pull all the injectors then there should be no compression at all. If the bubbling on cranking then stops that would that prove that compression is causing the gas in coolant so I'd be pulling the cylinder head. If bubbling continues with all injectors pulled then something else weird is going on :? .
Also, if i pull/replace injectors one at a time then crank it over, I may even find out which (if any) cylinder or group of cylinders is/are leaking.
Probably a major and glaring flaw in this theory - like i say never seen inside of a diesel head. Just pondering out loud while supping an ale really. If my pondering is total embarrassing cobblers (not unlikely) please advise accordingly before I do something stupid :facepalm: .
:idea: I'm wondering if, since coolant bubbles just from turning over on the starter, could i do a leakage test just using the starter motor? I've never seen the inside of diesel cylinder head, but I assume that if I pop out an injector from any cylinder then there's no compression in that cylinder? If that is right, then if I pull all the injectors then there should be no compression at all. If the bubbling on cranking then stops that would that prove that compression is causing the gas in coolant so I'd be pulling the cylinder head. If bubbling continues with all injectors pulled then something else weird is going on :? .
Also, if i pull/replace injectors one at a time then crank it over, I may even find out which (if any) cylinder or group of cylinders is/are leaking.
Probably a major and glaring flaw in this theory - like i say never seen inside of a diesel head. Just pondering out loud while supping an ale really. If my pondering is total embarrassing cobblers (not unlikely) please advise accordingly before I do something stupid :facepalm: .
