XJEEP01

Unexplained coolant loss. Oil is very milky and rising. Drop in oil pressure. I am exhibiting virtually all of the signs of a cracked cylinder head. I have been thinking about getting it tested or sending my oil out to check for coolant. I am pretty sure the head is cracked so I may do the latter just to assess bearing wear. My question is if the cam and bearings are shot, should I rebuild with the same engine, or would it just be cheaper to get an entire 6cyl and swap that in? Thanks everybody.

CrawdadSlim

Any knocking or unusual noises? If not and you caught it in time just replace the head. If your lucky you may just have a blown head gasket . Just curious, how many miles on the old motor? Ever overheat before the milkshake?

Firestorm500

Replace the head with aftermarket one. Totally rebuild the lower end.

Cutting corners at this point only leads to misery later.

Firestorm500

No. His drop in oil pressure, along with milky oil, shows the bearings are fried. He has the 0331 head, which is cracked. A $45 head gasket kit will not fix this engine.

CrawdadSlim

I wish I could diagnose a vehicle without even looking at it. I gave a vauge idea to the op, not a death sentance for his motor. What affect does coolant have on an oil filter ? Do all 0331 heads crack? You never know till you try. Thanx for chiming in. Multiple feedback is good.

Willys55

He used the x-ray eyes from his avatar.


Seriously, if the contamination to the engine oil results in pressure drop and milky oil coupled with continued use of the vehicle.......rebuild/replace bottom end. This would include bearings, oil pump, pick up screen/tube, resurfaced crank(or replace).

salad

ALL bearings. Like Firestorm said, cheaping out on one part will only lead to bad times at this point. Hate to say it but you really should've stopped driving it some time ago.

Another alternative is to grab a long block from another year and toss it in. Coil rail can be mounted creatively like so:

Cherockee

Rebuilding the existing block is possible, and it would be safe to assume at this point you'll need to do at least that. But honestly buying a new re-manufactured engine will be cheaper and will come with a warranty. Plus you will have a lot less down time.

Kalali

What about cam bearings? Wouldn't the contaminated oil/coolant oozing from the cracked head pass through the cam bearings before getting to the bottom end? Just asking.

bigbadon

Yup, and also the lifter bores. The lifter bores are seldom mentioned and they have the most impact on oil pressure. When the head cracks coolant puddles up and constantly flows into the lifter bores (and cam) especially the lifters closest to the crack. There are countless stories of new rebuilds with low oil pressure because the lifter bores were never checked. Now the bad news....this means a scrapped block or re-machining by a competent machine shop.

Firestorm500

It is because of your "vague idea" that I "chimed" in.

I have seen countless posts like this on this forum over the 4-5 years I have been on here.

I have also had it happen to me on 2 classic Mustang engines (I bought them that way).

Based on what he posted, there is really only one diagnosis, which I summarized.

Since you are a newbie, I forgive you.

Tony_SS

Any knocking?

I would pull and replace the head. I got mine from J&C enterprises... seems nice so far. Much thicker casting.

If you caught it early you might get by with just a head swap...If its knocking, time to rebuild it.

salad

"Catching it early" is like the same day it happens, not when your oil pressure has plummeted. No way out of that without a rebuild.

JeepsMyName

Salad I concur, I had a 0331 head crack with no oil.pressure at idle for a week some time about two weeks later I found milky oil... I immediately drained and flushed my engine. After the new head I have 18ish oil psi when hot at idle. If you catch the antifreeze in the oil soon enough and deal with it you could save yourself a ton of money!

IGeeky1

I think two things could cause low oil pressure at this point.

In the poster above, the low oil pressure was likely due to the thinned oil, it was mixed with coolant. Once the coolant was no longer mixing with oil, it was not as thin and took more force to be pumped ... pressure returned.

In cases where the coolant leak has been stopped and coolant is no longer in oil and the low pressure still exists, it is then likely due to worn/damaged cam bearings.

It is easy for me to see both scenarios.

If the head, gasket, oil and filter are replaced and the pressure is still low then the cam bearings are suspect. The bad thing is if it doesn't take care of the issue, then you will need to repeat a lot of work removing the head again to get to the block and remove engine to replace cam bearings. (of course replace crank bearings and lifters as well while it is out)