My 97 limited had a bad intake manifold gasket and had the valley full of coolant.

My 96 SR5 had a leaking coolant hose for the throttle body heat.

For the limited I committed to rebuilding the heads. Even though I could have just done the manifold gaskets I already had my spare set of heads rebuild and had the YotaShop head replacement kit on hand.

If you pull the heads it is very worth the 200 or so dollars for the kit. It comes with everything. Valve stem seals, headbolts, knock sensor cable assembly, exhaust donuts. It’s got it all.

Those compression numbers are not that stellar in my opinion. Hopefully a valve adjustment will help.


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I finally had some free time today to turn a wrench. Pulled the intake tube and opened the butterfly valve: no signs of coolant or dye. There is plenty of carbon fouling and a bit of oil, related to valves out of adjustment I'm sure.

I got a decent look at the valley between the head gasket covers by pulling a few things out of the way. No sign of the coolant dye. I don't think I have coolant pooling there.

Is there anything else I should consider before settling on a head gasket leak as the diagnosis for my coolant loss?

I do have a few neighbors who used to be mechanics. Both of them are willing to offer limited help, and think it might be a mistake to go halfway on this and skip the rebuild given the age of the motor.

The new supercharger release has me thinking, maybe I'd like to get some power back. Most of my driving is at 7000+ feet elevation. Am I right in thinking that slapping a turbo on this motor without a rebuild first would be asking for trouble?

I intend to keep this rig running. It's well maintained, in great overall condition, and well modded to fit what I need from it. Starting over with a new one would cost a hell of a lot more than fixing my motor issues. I bought it 10 years ago at 150k miles for $3500, and have been tinkering with it ever since.

This will be the offroad, camping, deep snow driving rig. The taco will stay closer to stock and be the daily driver workhorse.

The advice you folks give on the forum is invaluable. I appreciate you!

I have a 1998 tacoma with the 5VZ motor. About two years ago at 200K miles I also experienced small coolant loss. I just keep topping it off. I figure coolant is cheap and I only need to add about every six months or so. It’s my daily driver and now I’m at 326K and continue to top off. I haven’t bothered to diagnose because it runs great. I also checked compression and numbers were not that great but really, who cares, I just drive it. I did the passenger valve cover gasket and just snugged the bolts on the driver side cover. Amazingly the truck does not burn any oil. I figure I’ll just drive it until I need a major repair. If it’s not a lot of coolant loss, just keep an eye on the overflow tank and top off when necessary. I have never done anything with the valves on mine. If you can address the oil leaking you should be fine in my opinion. The 5VZ is an amazing motor.

New symptoms after a drive today. Longer drive, picked the wife up at the airport. About 80 miles in, noticed the MIL was lit. Code P0450, knock sensor bank 1. Also experienced rough idle and moderately reduced power. Possibly the leak is worsening, allowing more coolant into a cylinder?

Possible, however, the only way to know with testing. Need to have compression, leak down test done along with boroscope of the each cylinders.

You can mostly see head gasket leak with clean spark plugs. Bubbles in the antifreeze.

A head gasket leak will present itself. You just need to observe the signs.

Hope this helps.

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