It probably depends on the cooling system design. Here’s an overview.
2 Likes
Sorry I’m late to the party.
25 years ago, nobody would have given a second thought to removing a thermostat. I did it with my 1985 Buick Skyhawk, and it ran fine. I also bypassed the heater core when it started to leak. I did these things because I was content to drive a heap in South Florida for the time being. I also bypassed the radiator fan relay when it went bad.
I’d never do the same with my 1998 Civic though. I might bypass the heater core now that it’s a heap (if it starts to leak), but the cooling system is significantly more sophisticated than the one on my old Buick, so I would not drive it without a thermostat or bypass the fan relay on my Civic.
You should get a second opinion from another mechanic, but my guess is you have a leaky head gasket.
My '98 Civic had the same problem. It would overheat slightly when I got off the highway, and nobody could find the cause, particularly because the head gasket failure didn’t manifest as it does on most cars with oil/coolant contamination. I had to go against the advice of several mechanics to bite the bullet and get a new head gasket installed, but it solved the problem, and the guy who replaced the head gasket confirmed I did indeed need a new one, although none of the mechanics would admit it was the head bad gasket causing the overheating, even after replacing it fixed the problem.
3 Likes
George, thanks for that link. I had never considered that the thermostat opening closes off the bypass on some cars. Good to know.
To be fair, the mechanic said drive without it temporarily to see if it still overheated to help narrow down the cause, not drive without it forever. OP didn’t do what he was told.
3 Likes
@old_mopar_guy, It’s a 97 and I doubt it works differently than my old 97 Accord did. However he is in a different country and the vehicle may be made differently. IIRC I did have to replace the fans once because the AC side fan motor quit. Probably brushes but they assembled the thing so it could not be taken apart or repaired, the whole unit had to be replaced.
It’s not listed in the Service Schedule for replacement, so I’m sure there are plenty of people who maintain their cars faithfully but don’t change the 'stat until failure.
Just like those who don’t change brake or power steering fluid.
1 Like
I don’t think the basic premise of the cooling system has changed a ton since the advent of liquid cooling vs. air cooled engines. Rather, the engine management systems (the ‘puter) has come about, and now the engine (realistically, the computer) knows the difference between 180 degrees and 160 (or whatever the case may be), and the computer will adjust things (fuel mainly) according to temp. Back in the day, you had no computer. You could run no thermostat and the only issue was your engine ran cooler. And that’s not really an issue. Now, the computer adjusts the amount of fuel, etc. based on temp.
I think we said / meant basically the same things, but there’s a difference in semantics.
1 Like
Well, no matter the cause, the temperature gauge on my car reliably reaches operating temperature and then it never fluctuates in the slightest unless something is wrong. On every other car I owned before that, the temperature gauge would fluctuate within a normal range. My Civic’s normal range is at one spot on the temperature gauge, and if it’s half a centimeter past it, I know something is wrong.
1 Like
This is not necessarily indicative of overheating. Also, has the sending unit ever been replaced? How about the radiator cap?
Honda and Toyota (and likely the other manufacturers) of that era and onwards have a non-linear temperature display. The guage curcuit-boards are designed so that the needle sits rock solid in the centre within the range of normal operating temps. The coolant temps can actually be fluctuating quite a lot, in isolated locations of the block as well as overall without giving any indication. Just like your old engines this is normal operation. The design of the guage means that if it moves upwards even slightly there def is an issue.
Given the symptoms I’d be suspecting the 2nd stage of the fan (or a secondary fan depending on the design for that market); a potential air lock (less likely); or the water pump.
On a 97’ Accord… You will have 2 electric fans… One is the thermostatically controlled fan that uses the engine temp sensor to determine if it needs to cycle the fan. The other fan MUST run at all times whenever the key is on and the A/C button is pressed. It will do this with the engine off… or running and also regardless of what the compressor is doing.
No need to guess, just run this simple test… Turn the key on… press the A/C button… Got fan?
Not too much change in water-based cooling system design for automobile engines over the years, but there has been some important changes along the way, the invention of the double-poppet bypass thermostat for example. I think this is a fun and interesting read.