Hello friends, I have a 2004 Discovery 2 with 101,000 miles. Recently the car is starting to idle rough and I receive a SES code of P305 (Cylinder 5 misfire). Took it in and found low pressure on Cylinder 5 & 7. I replaced the spark plug and after 300 miles this with the the plug for cylinder 5 looks like. Based on this plug is it fair to say that coolant is leaking into cylinder 5 through the head gasket?

LR specialist says it's about a $2500 job but the car is only worth $6000 ?

Can you confirm that this plug shows evidence that there is a head gasket leak and what would you guys do? Replace the head gasket or drive it until it fades away into the pasture?

You advice is greatly appreciated.

Sincerely



Aaron East

 

It's not clear what you mean by "found low pressure on Cylinder 5 & 7." Does that mean the shop ran a compression test and found low values on 5 & 7? If so do you have more detailed compression test results? What were the values for the other six cylinders and what were the values for 5 & 7?

As for the plug you have pictured I don't think it indicates coolant leaking into the combustion chamber. I don't claim expert status but from what I have read and seen here a plug from a cylinder that has coolant leaking into it would be steam cleaned and would not have the deposits you have pictured.

More often than not misfires are caused by failed spark plug wires. What wires are on your truck and how old are they?

 

Here are the pressure readings from all 8 cylinders:

Passenger Side Bank
Cylinder 2: 180
Cylinder 4: 180
Cylinder 6: 180
Cylinder 8: 180

Drivers Side Bank
Cylinder 1: 180
Cylinder 3: 155
Cylinder 5: 130
Cylinder 7: 145

Also noted was that exhaust ports are leaking down and escaping through secondary air ports.

Do you think that it is worth the minimum $2500 investment on a $4500 car (which is actually in great shape)

Thank you

 

If coolant is leaking into cyl 5 it is not from a HG failure. It would be from a cracked block as there are no head related coolant passages on the middle cylinders, only on the ends.

I had this exact thing happen on Cyl 6 and the plug looked the same. fouled and gunky. My guess is because coolant seeps in when the engine is cooling off, then burns off when the engine is started up the next time. It would only be steam cleaned if there were a gusher of coolant in there and no firing.

If this is the case a head gasket repair would likely not fix the issue. Though that is not an out of line price for a HG repair, High end yes, but not out of line.

And if this is the issue you have two choices, 1: New block, 2: Block Seal in a can may plug the crack for a while in which time you can drive it till it dies and then change the engine if you like it that much. New block $5 - 10k installed.

Remember, you are maintaining a $40k truck, not a $6k truck. Regardless of what it is worth on the market now.

 

Your spark plug above doesn't look like a typical head gasket failure, but there are different types of head gasket failures (see pic below).

Does your exhaust smoke?

Does your oil look milky?

Does your coolant have a gasoline sheen to it?

Are your coolant hoses pressurized (hard to squeeze)?

 

To me, if your shop is honest the above suggests that your head gasket isn't leaking coolant...but is instead leaking your exhaust gasses from Cyl 5 into cyl 3 and into cyl 7.

Notice that your #5 spark plug is dirty instead of steam cleaned. It would be clean if your were leaking coolant.

The above is actually good news because it would *seem* that your block is fine. 180 compression #'s for everywhere else are nice, and the problem doesn't seem severe in Cyl #3, #5, and #7.

Since you want to be on a budget for a car with low resale value, I'd think that a shade tree mechanic would be willing to to your head gasket job with the block still in the vehicle...and since your problem is only on the driver's side then you just have to do that 1 head gasket instead of doing both driver's and passenger side head gaskets.

The bargain way means that you will not be paying to have the motor pulled from the vehicle and you won't be paying for 2 head gaskets, just for 1.

What you'll have to decide is it you want to gamble on the bottom Dollar repair by not paying to have the heads decked. With the motor left in the car you can't easily deck the block, of course.

For a bargain job (heh, most times you just get what ya pay for!) you might just replace the head gasket on the driver's side, or for a "good" job deck the driver's side head and go with a factory head gasket just on that side.


For a Top Dollar, by the book, "done the right way" repair you would have a machine shop deck the heads and the block, both (on the driver and passenger side). To deck the block means paying to have the motor pulled.






*If you don't send anything to a machine shop (i.e. save the most money up front) then you want to buy a composite head gasket (thicker, so it can handle more variances in the heads/block since nothing got decked)...but you don't want half of your motor to have a composite HG while the other half (passenger side) still has a factory HG because then each half of your motor would have different compression ratios.

So only go the composite Head Gasket if you are replacing both HG's on passenger and driver side.

When doing only 1 HG on 1 side of the motor, get that side's head decked and go with the thickest "factory" head gasket (not a composite!).

If going with a composite HG, then do the HG job on the full motor (both sides).

 

Thank you so much everyone for your suggestions. So great to have some valuable feedback on what to do.

Much Appreciated

Aaron