Coolant, hoses, thermostat, etc. all brand new. Issue, if it is an issue, only started happening when the outside temp has been dropping into the 20's and 30's... 98 Civic takes forever to warm up, and even when allowing to warm up in the mornings or from sitting for a while, the gauge moves very slowly. If you have the heater on, the needle pretty much does not rise for several miles. This morning, I was testing it, and set the temp to cold, and the needle came up to operating temp after probably 5 miles. As soon as I put it to heater, the temp dropped almost all the way down to zero on the gauge, and then slowly rose back up... I don't remember it doing this last year, but maybe it did...

 

did you bleed the coolant?

 

I assume that the shop did... however, BEFORE I took it in to the shop for the repairs, it was doing the same thing... so I don't think it's an issue of air in the system.

 

test the t-stat, lol 20's try -20 !! it's cold as fuq here.

 

T-stat is brand new. Its one of those fail safe kind...

 

Do you think the sender is going bad? I think its accurate though as when the temp on the gauge starts dropping, once you switch the selector to heat, the temp coming out the vent starts cooling, not as hot... takes a few miles before things get warm and the temp gauge stays pretty much at normal op temp... I let it warm up for 5-10 minutes in the morning... maybe thats not enough?

 

What did you take it to the shop for?

 

Water pump replacement (OEM was leaking). However, the issue was occuring BEFORE I took it in for service... and started once the weather got cold...

 

Not directly related, but I do find that my cooling fan never kicks on during winter. Last winter I thought maybe the fan died but then summer came around and my idle drops started happening again at lights when the rad fan kicked in.

The aluminum block and head are really good at dissipating heat. Didn't think it'd be enough to drop the temp by turning on the heater though.

 

Is your valve all the way open,when you have the lever to "heat"?
Don't forget, the hot air,is trying to heat up all of the parts in the heater area too.

 

Just repaired this in my 99 HX.

Replaced T-stat (was not closing all the way)

Hopefully they did replace the thermostat (might check) if so, probably an air pocket, most likely in the heater core itself (why the temps would fluctuate with heater use)

 

im having same issue myself......i installed a oem honda t stat. jacked up the fronf as high as possible. i got a funnel that attaches to the rad neck run the car at 2k rpms till temp came up halfway till fan come one i felt like the air was gone. i hit the road to test drive driving normal by the time i was at 60mph the temp was falling like a rock. the heat stayed hot though. ive worked on cars a while this got me stumped.
i been thinking of pressure testing the system again and check for small leak, then using my coolant system vacuum and see if it will hold vacuum if it wont i guess ive found my prob.

 

I vote for t-stat or air pocket behind it. Personally I'd swap to a genuine Honda t-stat.

i've used fail safes and they do work as advertised. Fail in the open position which means low engine temp. Or there could be a piece of gasket or sealant that has gotten loose and jammed the stat open.

 

throw some cardboard (preferably from a case of your favorite beer) in front of half the radiator. do it every winter. heat works better and warms up quicker

 

I think it's bad dude...

Fail safe t-stats will stay open when they break which means the car won't get up to operating temp. They're safe from making the car overheat is all.

 

Might have been air, and the symptoms described BEFORE the water pump swap maybe coincidence? Ran the heater on the way home yesterday, temp fell, came back up, and have not had any issues so far. Let car warm up for about 10 min this morning, ran heater half way, and drove to work. No issues that I could see... thx

 

Powerful heater to dissipate that much heat. You think you should still be able to have your heater full blast without dropping the temp that much, but hey at least you have a fix that works.

I wish my heater worked.... 20 degree mornings I look like I'm about to go play in the snow I have to bundle up haha.

 

You should try one of those 12volt heater fans that plug into your lighter...

 

You do understand how the heating system works, right?

When you turn on the heat, it opens a bypass allowing hot *** coolant to flow into your heater core, in the winter COLD air flows over it, by cold, I mean, stick your hand out the window while driving, yes, that cold.
It cools that fluid as a byproduct as it flows back into the cooling system.

There are some guys that put bonnets over their grill to help regulate the amount of cold air that is allowed into the engine compartment, in essence, forcing the compartment closer to 'optimal' temps.

 

Same thing is going on with my car it takes 20 minutes for it finally be at operating temp..

 

exactly ^^^

 

This is pretty typical with Hondas from my experience. Neither of my Civics would sit over half on the gauge, even with new senders.

Hell my friend drove his Accord around for over a year with a broken radiator fan. Never overheated even in 100 degree weather in stopped traffic. If it started to get warm he'd crank the heat up for a few minutes and it would come down below half again.