Coolant leak, Cyl 3 misfire, intake manifold?

[dcarcagno]

Hey,

I’m having a slow coolant leak in my 01 lx. I recently started getting p0300 and p0303 codes intermittently. Only once have they cause the vsc trac lights to come on. I pulled the plug for Cyl 3 and it looked cleaner than the others. I put my boresope in the tube and it looked like maybe there were a few drops of liquid along the wall dripping from above. I think I might be burning a tiny bit of coolant on first start but it’s also been cold so it’s hard to differentiate between that and normal condensation. I replaced the radiator already. I’m thinking it’s the intake manifold leaking into the runner? I don’t see any other leaks. I’ve looked in the valley and didn’t see anything. I’ve looked under the throttle body and it’s all dry as well. The oil looks clean, and no exhaust gases in the coolant after a test.

 

[rexington14]

Did it overheat recently? Is the #3 piston top obviously and noticeably cleaner than the others?

Change the oil and send a sample out for analysis. Oil may look fine to the naked eye but the lab tests for antifreeze in the oil is of course much more sensitive and accurate. This will tell you for sure if trace amounts of coolant are getting into the oil. $40 for a Blackstone analysis.

Other tests to consider are compression test and leak down test. Maybe a couple hundred bucks at a shop.

 

[dcarcagno]

I ordered a blackstone kit. I’m definitely burning a tiny bit of coolant. But only at startup, no smoke or smell while driving or after driving for a bit. I used my boresope to look under the manifold and found some dried spots that looked like coolant possibly. I’m going to take the manifold off this weekend and check for sure. The piston looked like the others, only the #3 plug was cleaner.

 

[2001LC]

Very likely a head gasket leak.

Intake manifold (IM) doesn't have coolant passing through. Whereas liquid, could be travel outside along intake manifold just below head covers. Then, seeping into intake port. Passed a bad IM gasket or when IM not properly bolted down (torqued). This would be vary easy to spot. Just looking along outside, where intake manifold bolts to head, along head cover. Liquid would be seen in cylinder with borescope, coming from intake valves.

Sure sign of head gasket leak:

• #3: P0303 cylinder #3 misfire
• #3: Drip of liquids, seen inside cylinder. Coming from head gasket.
• Coolant seen in valley, coming from heads gasket. Very likely warped head. From being over heated.

Number one reason this happens. Is when engine run low on coolant, the over heated.

Inspection procedure, all 8 cylinders with bore scope. Looking for coolant.

1. Make sure coolant level to the top of radiator and all air out of system. If not, top rad, bring engine up to operating temp of 187f. Then bring RPM up to 3K for few minutes. Test that HVAC heat, blows very hot front and rear. Park with front end higher than rear. Vehicle must also be cross level. Then let cool down for 8 hr. can be less cooling time in winter. Check under radiator cap. If low top Rad and Reservoir, and repeat procedure. Repeat again if needed.
2. With coolant topped, air burped & engine cold. Pressurize coolant system to ~15 PSI.
3. Inspect each cylinder with bore scope. Looking very close along head gasket at top of cylinder.

Any coolant even a tinny drop. Head gasket is leaking. Head may or mat not be warped.

Sign of warped head:

Head gasket leak between #3 & #5 cylinders

Head gasket leak seen from outer sides of block

If cylinder walls look good. Very likely short block (block, pistons rings, crank & bearings) are fine. Pull heads, inspect have machined if needed and replace gasket.

 

[dcarcagno]

Doesn’t the lower intake manifold have coolant passages?

 

[2001LC]

Doesn’t the lower intake manifold have coolant passages?

No part of intake manifold has coolant passages.

 

[2001LC]

 

[dcarcagno]

I’m losing my mind. Haha. I plan on taking the manifold off today and doing a coolant pressure test. I should be able to see the mating surfaces at that point. I just repaired the head gasket on this engine. I feel so dumb now. I used a precision straight edge on all the surfaces and cleaned well.

 

[2001LC]

No need to remove IM, to inspect cylinders for head gasket leak.
If coolant not observed, with borescope, on/from head gasket. Shortly after pressurizing coolant system. Pressurize continuously for 8 hours (over night), check again with borescope.

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