Cat 977L - overheated it, and now water in cylinder 1 (Cat 3306 engine)

JohnnyAirtime · 2025-12-24T17:51:19.000Z

Good day gents.... I recently aquired a 977L (along with a 931B - and love'em as they have 4-in-1 buckets). However, when I took posession of it off the trailer I had to drive it from dropoff location down into a canyon and back up to my house via a steep switch back. About a mile long dirt path. My 1200ft long driveway is concrete and steep up/down with turns. Not nice for a semi with lowbed. I didn't check the coolant (or any fluids actually) before doing this... but the 977 had run fine when being worked on for cylinder seals and other "fixes" before I took posession. It was part of the deal. When I was coming UP towards the back of my property, it started to get hot. I was in 2nd (yes, my mistake - new operator/owner issue) but couldn't stop (too steep). I idled it down, sat and let it cool down, then moved the last 20feet to a flat switchback turn. It was about 85 degrees out that day. I came back that night, now only 55-60 degrees and put 4gal of water/coolant in the rad. Drove it up to it's resting spot (longer than the first leg and this time in 1st gear), and later added another 6gal to "fill" the rad. That last run up to the resting spot it never got hot or even too warm. However, when I went to start it the day or two later... it blew water out the exhaust. It was pressurizing the radiator too (cap off, water is blowing out the cap - not just water pump movement). Now... the head is off, and no tell-tale visible signs of it just being a head gasket. But cyl 1 was full of water. Also, the precup on cyl 3 was loose. Finger tight loose. I'm in San Diego.... anyone know of a place to get the head checked? Or, would it be better to just buy a reman head and go from there? I'm hoping the cylinders are okay and we don't have a cracked block. The pressure in the rad was quite a bit... seemingly more than just a crack could enduce. But... I'm not a mechanic, it just seems like common sense. If I buy a reman head.... know of any places with such?! My mechanic knows, and is waiting for me to call local machine shops. But they aren't too many around anymore. Plus, it's Christmas Eve! THOUGHTS from the 3306 experts?!

Started by JohnnyAirtimeDec 24, 202545 replies

JohnnyAirtimeJunior MemberFeb 2, 2026#41
pittsburgh cat man said: I think I would pull the panel off the back of the machine by the battery and see if return spring is there Click to expand... .... The 931 pressure valve is under the seat/foot floorboard. I'll look there first and lubricate valve lever and pedal swing assembly to see if it helps.
JohnnyAirtimeJunior MemberFeb 4, 2026#42
pittsburgh cat man said: I think I would pull the panel off the back of the machine by the battery and see if return spring is there Click to expand... Done.... and yes, two springs there actually. I cleaned and lubricated... and excersized the rod and joints. Now... moving freely and MUCH easier to manuever!!
JohnnyAirtimeJunior MemberFeb 12, 2026#43
The reconditioned 977 head.... nice and purteeeee.... Awaiting install
JohnnyAirtimeJunior MemberFeb 19, 2026#44
Hurry up and wait over here.... Too much rain, mechanic(s) are sick, etc.
JohnnyAirtimeJunior MemberMar 26, 2026#45
Well.... see if this posts; (oops, can't post video - so here's a picture) She's back together, and purring like a kitten. .... so yes, the 977L with a 3306 has been repaired. No more issues with water/coolant in the cylinders. Reman the head, new pre-cups/seals, and of course gasket kit. The valve cover, rocker arm assembly also all cleaned up and inspected. Need anymore details? Let me know and I'll do my best to answer.
JohnnyAirtimeJunior MemberMar 26, 2026#46
bam1968 said: I'm going to go out on a limb and say that this was an issue before it got delivered to you. How long did it run from the time you unloaded it until you noticed it was hot? 20-30 mins? If so, I am pretty sure you would have noticed that much coolant/smoke coming out of the exhaust if it just happened when it was delivered. BTW there is nothing wrong with running it in 2nd gear. I'm not a fan of running them in 3rd gear but second if fine. ........... I hope you get lucky as coaldust said and it's only precup leaking. Click to expand... When I go back and re-read posts... THIS post, hits the nail on the head (literally). Thank you for the intel and valuable info!

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