Blown Head Gasket
#1
Blown Head Gasket
1987 Jaguar xjs V12- numbers matching. Pristine condition, and a 3 year old paint job (champaign). Bought it for 2k on a hunch that the owner was wrong about a it having a blown head gasket. There is no smoke or excess noise. The oil is not milky colored. Idles and cranks smoothly. It does have a lack of power however. It does overheat. The car leaks about a quart of coolant on the floor over 1-2 weeks. I have already replaced a cracked coolant hose which helped dramatically. Could the fact that the cooling system cannot fully pressurize because of the leak be the sole cause of the overheating? Additionally are there other ways to check for a blown head gasket without tearing into the engine? I can't take it to the mechanic for a couple weeks because I'm short on money.
All the best,
Lou
All the best,
Lou
#2
#3
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IMHO the best way to check for a blown head gasket is to test for hydro-carbons in the coolant. You can buy a "block test kit" (about $50 from NAPA Auto Parts) which uses a liquid dye or take it to a shop that has an exhaust gas analyzer....which can be used to "sniff" the coolant.
Go through Don's list and there's a 99% chance that you'll fix the overheating.
Cheers
DD
Go through Don's list and there's a 99% chance that you'll fix the overheating.
Cheers
DD
#6
I spent several days checking different parts of the cooling system. The car sill overheats with the electric fan remedied. Then I made sure there were no air bubbles in the cooling system. After that, I replaced the radiator caps. (one was slightly leaking but both were replaced for good measure) The PO said he replaced the thermostats and I am sure he did because he gave me the old ones with the car. There is a mystery smell of evaporated coolant in the garage after running it. Now I am looking for leaking hoses. I already found and replaced one cracked coolant line which helped dramatically but the smell remains. I might just have to bring it to the mechanic but money is tight right now so it will have to wait a little bit longer. continuing with self diagnosis attempts...
Last edited by EcbJag; 01-07-2011 at 02:31 PM.
#7
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Update: Today I took the car for a drive after repairing a suspected leaking coolant hose. The car never overheated although after a 10 mile round trip it was creeping up toward the "N". It seems like a mild problem as of now. When cruising at high speeds the car runs well and cool; it's stop lights that kill it... THEN: upon returning home I found the possible source of my electric fan problems: a blown inline fuse for the electric fan which has been inop since I bought the car (it has been overheating since I got it in July so I haven't even really got to drive it yet!) I will take it for another drive in a couple days, observing how much coolant is still leaking onto the ground and seeing if the electric fan works! wish me luck! if I could fix the overheating all that would be left to fix would be the strange delay from the gas pedal to the engine response.
#11
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"Moving towards" the "N" is fine, usually.
You might want to buy or borrow an infrared thermometer (you know...they look like a ray gun) and check temps at the left and right water rails and then look at your gauge. It's nice to know what temperature corresponds the the "N" rading on your guage....and it can vary quite a bit from car to car....as much as 20º. The gauges are not all that great.
As I recall the bottom of the "N" on mine was about 180º and the top of the "N" was about 195º. Yours may vary.
Anyhow....
It's good to know if your left and right banks are about the same temp as it suggest proper coolant flow thru the system and the segregated radiator. This is important because "overheating" is the typical sense isn't necessarily what hurts these engines. Lack of proper flow can cause steam pockets....localized overheating....in the cylinder heads even though the overall coolant temperature is well within the safe range.
Cheers
DD
You might want to buy or borrow an infrared thermometer (you know...they look like a ray gun) and check temps at the left and right water rails and then look at your gauge. It's nice to know what temperature corresponds the the "N" rading on your guage....and it can vary quite a bit from car to car....as much as 20º. The gauges are not all that great.
As I recall the bottom of the "N" on mine was about 180º and the top of the "N" was about 195º. Yours may vary.
Anyhow....
It's good to know if your left and right banks are about the same temp as it suggest proper coolant flow thru the system and the segregated radiator. This is important because "overheating" is the typical sense isn't necessarily what hurts these engines. Lack of proper flow can cause steam pockets....localized overheating....in the cylinder heads even though the overall coolant temperature is well within the safe range.
Cheers
DD
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EcbJag (02-25-2011)
#12
Ok. I'll see if I can find my Infrared thermometer :-). Reading other threads about overheating it sounds like 220 degrees is technically overheating? I am starting to suspect a marginal radiator because at cruising speeds there are no problems but at stoplights when it loses air flow, it starts creeping up. The thermostats are new so I believe they are fine (unless I got duds) Another thing is that it is pretty cold here right now, 40 degrees average and it could be masking a more serious problem.
#13
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EcbJag (02-25-2011)
#15
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As radiator removals go, it's a PITA....but entirely DIY-able. The lower radiator hose is what makes b*tch to deal with. The rest is straightforward enough.
I strongly suggest having a helper ready when the time comes to lift it out or you'll bang it up pretty badly. It has to be lifted up and canted rearwards simultaneously. Awkard for one person to do on his own
Cheers
DD
#16
After 8 months of struggle I finally broke down and saught a power greater than myself as the spring months creep in and the problem intensified- the local mechanic. He has the car now and will get to the bottom of it. I found the radiator job best left to him if need be. I should have closure to this in a week or so an a working car! will keep up to date..
#20
tbh with you man Id go check that **** out in a junk yard because thats pretty pricey for that little sensor.
Last edited by sidescrollin; 02-28-2011 at 02:51 AM.