Intake Manifold Coolant Leak & Compression Test Results

Hi Folks! A couple things here; hopefully this isn't too overwhelming to read. Appreciate any feedback that y'all can provide.

I'm trying to gather some more info on a coolant leak I've been experiencing on my '95 Tacoma 3.4 (~234k miles). The evidence of the coolant leak is in the valley between the passenger side valve cover and the intake manifold (dried coolant; see photos below). I'm losing a bit of coolant, but not enough to be overly concerned; top off reservoir every several months or so, but haven't done any big trips in some time. A mechanic friend of mine took a super brief look and indicated that it could be the Lower Intake Manifold Gasket. Another thought was maybe the coolant bypass hose.

After combing the webs for more info I began to worry that maybe it could be an issue with the head and/or head gasket and wanted to try to to rule that out. I performed a block test (result: no exhaust gasses in coolant) and a compression test (results below). Spark plugs looked fine and saw no coolant when plugs were removed. I'm not super confident on whether the results I got are acceptable or indicative of an issue, so some feedback would be welcome. Linked here is a video of my truck starting up and the initial exhaust. Does this look like coolant or just normal condensation burning off? Seems to only be white for a few seconds upon startup and then appears normal after reaching running temp.

Compression Test Results:

• Cyl 1: 175 psi
• Cyl 2: 166 psi
• Cyl 3: 162 psi
• Cyl 4: 155 psi
• Cyl 5: 162 psi
• Cyl 6: 150 psi

Questions as follows...

1. How difficult of a job is doing the lower intake manifold gasket? Any other considerations to go along with this job, ie. replacing hoses, other gaskets etc.? I also need to do the valve cover gaskets; would this be worth doing at the same time since the plenum will be off anyway?
2. Are the compression results a red flag in any way, indicating an issue with the head/head gasket? Is there any way to test the exhaust of of the tail pipe to be confident there's no coolant present?

I'm fairly confident I could do the lower intake manifold job myself. Since I don't need the truck as a daily driver I could have it in the garage as long as needed and would be stoked to learn along the way. However, if its a HG issue, I'd be hesitant to get that deep in and would probably have a mechanic take it on.

Thanks for any input, appreciate all the knowledge imparted by these forums!

-Garrett

 

Exhaust looks normal especially if it's cold and/or damp out, if you had coolant leaking into a cylinder enough for it to come out your exhaust you would likely have a misfire especially on the first start of the day. Have you checked the coolant hoses going to the throttle body? they would be more likely to leak than an intake gasket and would cause crusties like that to build up on top of the engine.

 

if the lowest compression reading is within 10% of the highest I wouldn't worry too much. The 10% number is kind of arbitrary but more than that leads to a shaky idle.

There are coolant passages that run between the heads through the lower intake manifold and it appears that this might be the cause of the coolant creeping up the bolt. This should be more apparent cold rather than hot but I bet your truck will make a liar out of me. You can borrow a coolant pressure tester from some auto parts stores... put 15 psi on the system a few hours after you shut her off and take a look.
Fixing it could be an issue. The heads or intake manifold could be so corroded that replacement might be necessary... RTV smeared between the 2 when put back together can put this off for a bit but is not the recommended fix.

Have you tried putting a wrench on the lower intake bolts and tightening them yet? It could be that simple...

 

Seemed like it's leaking from your lower intake manifold gasket, which is pretty common. The gasket is sandwich between the intake manifold and cylinder heads, which contain coolant passages.

I would recommended changing the knock sensors and harness while you're there already.

 

Any idea for the torque specs for the intake manifold? 3.4

 

@kskin Haynes Manual says 22 ft/lb for the Intake Manifold bolts, working 'from the center out'.