My '98 blew through the gasket from the cylinder to the water jacket so the obvious issue was that it would overheat (combustion gasses collecting around the slug on the thermostat so that it could not sense temp properly and closed. And then since there was no coolant circulating, over heated - which then blew the bubble of gas and a lot of coolant out of the system and all seemed fine for a while.) Eventually it got to be an all the time issue, so I pulled the thermostat out, removed the guts and reinstalled the shell (there's an o-ring type thing on the thermo flange that you need to keep to maintain the seal on the housing.) That allowed me to drive it while I decided on what to do. Got prices in NY and got discouraged (along with at least three shops that said they wouldn't touch it.) Went to my tire place across the state line in Joisey and asked for his recommendation - his guy said 'Sure, I'll do it', pulled out his 'log' and quoted me what the last one he did was - and his price was at least $1200 less than what I found in NY.
Other symptoms are oily crud in coolant overflow tank, oil and or coolant leaks on outside of block.. I also would bet that you just might be 'wearing' the original timing belt if no gasket has been replaced yet. That might be the scary part since it is a dual-cam engine and if belt goes with engine running really bad thinks happen due to the laws of physics when a valve tries to occupy the same space as a piston. When that happens you have a BIG four cylinder, DOHC, horizontal opposed door stop and the car then is worth scrap value...
Asked my friend when his blew - he said 147k - his was 2002 but he had electrical issues (like a fire in the fuse box.. ;-) so there was no thought on his part about fixing it. His had the overheating issue but he's not mechanical so he never thought about 'modifying' the thermostat to allow him to drive it. If he had done so he probably would have been able to get a better deal on a replacement vehicle because it wouldn't have been an emergency.
What symptoms do you have that are making you think head gasket? Other than the current mileage which if it is original gaskets is a good enough reason to think replacement.
Another thought... is yours turbo?
NA, no turbo. Rough running on start and slow engine response (slower than usual even) are kind of pointing the way. It’s a weird single cam engine but I still don’t want the timing belt to go out on me and that’s my main concern with it. I had that happen on a Chrysler product and it was a pain to sell afterwards.
I love the Baja but not enough to not get rid of it if maintenance is too much money to be worthwhile. I’ll prolong my payments for another year and pick up an XV Crosstrek and wear that out playing rallycar for a while.