ALH Beetle getting hot

1999 Beetle 5 speed. Recently started overheating on long pulls over mountain passes. It got up to 220, so I pulled over. By the time I got pulled over and stopped, it reached 240. Temps are read by an Ultra Gauge. Let it sit and idle for a few minutes and it cooled off. I smelled antifreeze, so I popped the hood and it had pushed some antifreeze out of the bottle. Made it the rest of the way to my destination by babying it on the big hills. First thought was thermostat was stuck, so removed thermostat for the drive back home. Still overheated on the way home. First 2 hills it got to about 210 at the top. Biggest hill it got to 220 then 240 again. Compression test shows 500-480-430-430. Has metal water pump impeller that has been checked.
Timing belt, tensioner, idlers, and water pump replaced 20k miles/ 11 months ago.
Radiator replaced 70k miles/ 3 years ago
EGR cooler removed and bypassed 3-4 years ago.
Without the thermostat it would run about 120 driving 75. As soon as you start pulling a big hill it would climb fast. Once out of the mountains it runs normal. Any ideas where to go next?
Sorry for the long post, thanks for the help.

That's not a long post, that's a complete post, as I read it you answered the question I was preparing.

Is it modified or stock?

Where is your timing? Maybe if your start of injection is advanced it'd make more heat?

Are you running bio or straight diesel

Are you using pink coolant?

Has your cooling system ever had stop leak in it?

Sent from my Pixel XL using Tapatalk

I forgot to mention it has 289k miles.
It has had PP764 injectors since 171k miles, other than that it is stock.
Timing is just below top line.
Straight diesel
Always G12 or G13 coolant
No stop leak since i've had it, and I have replaced every component in the cooling system since I have owned it.

I have had to add maybe 1 cup of coolant a month for the past few months, maybe a cup every other month. Its not much.
When I say the temp rises fast going up a big hill, I mean from 180 to 220 in 15 seconds. At this point I am leaning towards head gasket, but I figured the comprssion numbers would look worse if that was the case.

Check your coolant for hydrocarbons...sounds like a head gasket to me, hopefully someone else has a better diagnosis

Sent from my Pixel XL using Tapatalk

It’s gonna be a head gasket , went through this exact thing at 394,xxx miles.... hard pulls temp would skyrocket, if I wasn’t aggressive then the temps would hover around 200 degrees.
I ended up replacing the head, and using ARP studs after I made sure the block wasn’t warped.

Yeah, that's what I expected. I'll pick up a hydrocarbon tester tomorrow to confirm and probably end up pulling the head. Thanks for the replys.

Have you tried running it with a known functioning thermostat?

Sounds possible you had a sticking tstat first and that caused overheat, then removing the tstat also caused another round of overheating. These engines and any engines using a thermostat design like these are NOT designed to ever run with no thermostat at all. Unlike some tstats that simply open to allow coolant to pass or close to block it, these thermostats have a secondary function for closing the bypass passage through the block. That's what the round plate that points inward on the back of the tstat is for.

When the thermostat is closed, the front part is sealed shut to keep coolant from being pulled from the rad, and the back part is open to let it recirculate through the internal bypass. As the thermostat opens, it's designed to both begin letting cooled coolant in from the rad, AND also close the internal bypass.

Thus if you run without the tstat in place, it doesn't simply force full flow through the rad like it would on an old Chev 350, rather, it can actually have the opposite effect and cause overheating since there's only some flow through the rad and also always quite a bit of flow through the bypass circuit in the block without it there.

I'd start by putting a brand new, high quality thermostat in it, especially since you will eventually need to do it anyway. See if that makes a difference before buying expensive tools or tearing the head off..... It might still be a leaking headgasket, but they're not a common problem area on these motors so best to rule out the easy stuff first.

Thank for the info d24tdi. I got the Block Tester this morning and confirmed the head gasket is blown, unfortunately. I assume Frank06 is still in the cylinder head business?? From what I have read, its time for replacing valve guides and camshaft anyway, might as well have someone go through the head.

Yes frank is the man to go for a head exchange.