baffled - coolant leak

hatemy850 · Post by **hatemy850** » 09 Sep 2010, 23:26

i have a 99 v70 cross country, and the plastic end tank on the radiator cracked. the temp indicator never said the car over heated, but it was 115 that day, the car died and was hard to start.

i have replaced the radiator, thermostat, and reservoir cap. my compression is 150, 135, 145, 120, 150. I have no oil the antifreeze, and the oil has no signs of water.

BUT, when i drive the car, within twenty miles, the reservoir is empty. the coolant is actually being expelled through the reservoir cap (keep in mind this is a new cap). so the pressure in the system is exceeding 22 psi / 150 kpa. but the temp indicator is within normal range.

there has also been an odd whistle during test drives. it is the reservoir cap.

what do you think?

Post by **renns** » 10 Sep 2010, 08:45

Sorry to say it, but I suspect a head gasket leak. A leak-down test rather than compression test would be a better diagnostic tool.

Post by **jblackburn** » 10 Sep 2010, 08:58

+1. And warm the engine up before you do that, sometimes a failed head gasket won't show any signs of leaking on a cold engine.

hatemy850 · Post by **hatemy850** » 10 Sep 2010, 15:49

Thanks, I suspected that might be the case. I didn't want to yank the head prior to getting a second opinion.

Would it be worth trying to retourqe the head, or give it up and replace the gasket?

Post by **JDS60R** » 10 Sep 2010, 19:36

A leak down or combustion gases test should be done before the car is driven again.

It appears you will have an issue and if so ,give it up and replace the gasket - do it before you drive it again. The whiteblock motors ,like yours, all fail the same way. The gasket goes, you get a very short amount of time, then the leak is big enough and the water enters the cylinder (sometimes overnight) and on restart or running the cylinder wall fractures(down the centerline of the motor).

If you catch it now you may not have to replace the block. It is considerably more expensive and time consuming to replace the engine vs. pulling the head and measuring for warp etc. If the block is warped you will still have to pull it but most of the time the head being serviced ( change your oil seals while its out - both valve and cam seals )and skimmed will produce a quality repair.

Please let us know how square your block and head were.

hatemy850 · Post by **hatemy850** » 10 Sep 2010, 21:59

Okay. Thanks, I will begin to pull the head tomorrow. A couple more questions before I get started.

Will I be able to visually see a fractured block? If I am getting pressure from one of the cylinders into the cooling system, is that even possible from a head gasket? Or is it more likely that the cylinder is cracked?

Post by **JDS60R** » 11 Sep 2010, 11:52

You should not pull the head until you have completed the leak down or combustion gas test . Unless you have something else to drive and nothing else to do.

Is it possible - YES. The head gasket failure is the most common cause of excessive pressure in the cooling system. You should replace the head bolts, thermostat , cooling reservoir and the pressure cap if the head gasket repair is needed. The system should be completely flushed as well.

You will be able to see the fractured cylinder if you have one -its very noticeable.The cylinders have cut lines between them down the centerline- they will be pressed together and will show a crack. You should have the head pressure tested while you are having the machine shop skim it and replacing the valve seals. Or get a replacement from Clearwater if its cheaper.

Once again - although very likely - it is a Mistake to take off the head without first diagnosing the leak source. Pull the plugs and pressurize the cylinders to find out which cylinder/s has the leak. Then you will know where to look. I do not suggest running the motor any more. Pressure of 100psi normally will overcome mostly head gasket leaks that are plugged due to the engine being cold. A combustion gas test would be the fastest and easiest. Spend a few bucks- get a result and then you will know if you need to pull the head or not. If you have pressure from the turbo entering the system you will regret pulling the head for no reason.

If the head comes off - have it skimmed, measure the deck, replace the oil seals, test the valves for leaks and play in the guides, clean up the threads and clean up the passageways . The only good part of a head gasket failing on this motor is you get to freshen up the head while its off.

Failure to replace the pressure cap (again) and a thermostat will cause a failure again shortly after your repair. Once the motor has blown past the cap the cap and thermostat can no longer be trusted. I also replace the reservoir and flush the system.

hatemy850 · Post by **hatemy850** » 13 Sep 2010, 23:30

Very comprehensive set of instructions. THANKS. I will follow these to the letter and let everyone know how it goes. At this point, I will solicit professional repair.

davis911s · Post by **davis911s** » 25 Nov 2010, 15:07

Any updates on this?

Was it your head gasket or something else?

hatemy850 · Post by **hatemy850** » 06 Jan 2013, 22:44

Leaky head gasket was the culprit. Well sort of. I found out after removing the head that one of the head bolts was completely broken. Not sure if the broken bolt caused the head to warp, or the head warping caused the bolt to break. No matter; I had to replace the head (and the bolts).