Help! My 91 Prelude 2.05 SI ABS is overheating.

(Sorry to invade a Civic forum with my Prelude, but after an exhaustive search I’ve found that this forum has more experts and experienced people helping out then any other site. If it helps, I had my mom trade in her expensive, always breaking down Pontiac Grand Prix for a 95 Civic DX[sm=smiley20.gif]).

Some background…
I bought the car back in 97 with 48K and I now have 138K.
I’ve been having the Honda dealer do all of the advanced work
-Clutch 4 years ago (clutch went bad)
-Timing belt 3 years ago (general maintenance, no problem with the old one)
-PCV valve 3 years ago (going through tons of oil, white smoke from dip stick)
-head gasket & coolant hoses 9 months ago (similar overheating problem as now)
-I installed a new cat-back system 3 months ago. (Honda wanted 700$ plus labor.. WTF)
-New speed sensor 1 month ago (400$... whish I’d found this site then, soon after that I’ve been overheating)
-I installed a new thermostat unit yesterday, no help…

Overall my Prelude has been very good to me, but now I’m starting to wonder if it’s time to start looking for something newer. I don’t want to after all the money I’ve put into it, but if I’m going to have to do this every 6 months then I have to stop the bleeding soon…

Overheating Problem
Ok, here’s what’s going on and what I’ve done…

Problem started after I had the speed sensor replaced about a month ago. I’m not sure what they had to take off to fix this… perhaps they screwed something up???

It was in the 70-80’s back then, as of today the high is 52 / and the low is 32. The problem is getting worse, such that I have to fill the radiator every time I go to drive and sometimes have to stop and re-fill on the way.

When I start my car up it idles hard (quickly revs between 1200 and 2500 RPM). With coolant levels filled up (both reservoir and Radiator) coolant gushes out of the reservoir ever RPM spike). With radiator cap off big air bubbles blow out.

-Driving
Going to work and back I now have to use the interstate. No problem with overheating, and the heather works, but after getting off the interstate if I don’t go straight home I start to overheat within 5 miles or so.

Driving to work via the back roads (which I prefer due to the shorter time) I’ll start to overheat within 6 miles or so and I don’t have any heat the entire way. By then all my coolant must be blown out.

It’s about 1 mile to the interstate, 15 miles on interstate and then 1 mile to work (70-55 mph)…
Or it’s about 8 miles on the back roads to work (35-55 mph).

If I drive around for awhile before getting on the interstate I overheat basically the entire way. (start out ok then I fluctuate up and down, each time going higher… no heater)

9 months ago
My car was overheating much like it is now, I’d just moved and started a new job so I didn’t have the time to investigate the problem like I should have.
I took it to Honda, they checked for leaks, did a pressure test (all negative) and then filled it up with radiator fluid and sent me on my way telling me they didn’t find anything wrong.
About a week later I was back and they looked at it again and couldn’t find anything.
Another week or so later I was back and that time I’d noticed steam and liquid coming out of the reservoir. They said they thought it was a blow head gasket, and while replacing it they said my head was warped and the sent it out to have it smoothed out. Until now I haven’t had any major problems, every time I fill up with gas I top off the reservoir with coolant…

1 month ago
I had no speedometer / odometer so I had Honda replace the speed sensor. Shortly after that the overheating began.

What I’ve done:
I’ve been trying no to screw up my car any more then it already is so I’ve stopped and topped off as soon as I get too hot.

Yesterday I replaced the Thermostat unit, no improvement.
Radiator fans work when overheated.
Oil looks normal.
Slight “oily” look on the top of the radiator fluid… just a haze…
Radiator looks clean, no dents, just a few bugs.

I’ve read though many of the topics on this subject here and have come up with a game plan of things to look at…

1) Replace radiator cap (I replaced it a few years ago.. don’t remember if it’s OEM… It can’t be this simple can it???)
2) Check for radiator blockage (I think the top radiator hose has flow, but I’ve only checked it after idling (after all my fluid has been blown out… need to check after interstate driving).
3) Check water pump.
4) Compression test.
5) Suggestions welcome and appreciated….
6) My car has been leaking oil while running. The guys at Honda suggested replacing a number of seals (including oil pan seal), said it would be cheaper to replace the timing belt and seals while I was at it. My understanding is that when checking the water pump you’d have to do this… and that the head gasket would have to be replaced at the same time, is this correct??? *Edit* - yep, water pump hooked up to timing belt.. Do'h $$)

I’m thinking right now that it’s not the head gasket due to the fact that I don’t overheat on the interstate… Unless it’s a problem with accelerating, thus creating pressure spikes.

What do you guys think? Am I on the right track or overlooking something?

Thanks in advance for your help.

KS200

 

thats a big post so I`ll go striaght to the point check your water pump My civic did the same thing add water and cant find where its leaking from.

 

Try getting a radiator overhaul and having your idle setting checked. If your rad cap bubbles, it's most likely to be a clog in the radiator... Had the same problem with my '96 Civic VTi.

 

Sorry about that..

Thanks for sticking with it and your advice. After looking into it and searching the forum I found this thread in which BoostEK suggests that it could be
As I think the speed sensor is near the thermostat plug I'm thinking Honda may have screwed the plug up when I had it in a month ago.

I'm not sure what the "thermostat plug" does, would this cause my problem... seems like it would just tell me that the engine is hot but not cause any overheating. (the water pump is mechanical, connected to the timing belt and runs as fast as the belt... right??)

Am I on the right track??? I'm trying to put off making the decision to replace the timing belt / head gasket and water pump as it's looking like it will cost just a much as my car is worth.

Thanks,

KS200

 

Ok, thanks...

I think the idle speed is ok... It doesn't always idle bad, typically just when I start up (after driving for awhile) and when I'm new the end of my drive (no problems right after I get off the interstate until I hit the 2nd or 3rd stop light)... I'm thinking it idles like this because it's trying to get more radiator fluid from the resevoir... No problems when I start-up cold.

I've yet to see anything come out of the radiator cap, it always spews / steams out of the resevoir fill valve. Should I have anything comming out of the Rad cap? Perhaps this is a problem with a potentially non-OEM cap.

Thanks,

KS200

 

Normally, the radiator cap is supposed to prevent water from escaping the cooling system... Different radiators have different radiator caps with specific pressure limits, so if anything spews or bubbles out of the radiator cap, either you have a cap that doesn't meet your radiators standards or there something in the radiator thats clogging it up causing excess pressure.

 

Thanks for your replies and help,

While looking up some more info about your suggestions I found a thread about checking to see if you fan is working, mine does work but the more I think about it it doesn't seem to come on all the time...

With a paperclip I checked to see if they would come on, and they didn't! I checked all the fuses and they were good, I then decided to pop in a 25AMP fuse in place of my 15 (the one near my steering column)... And go figure the drivers side fan came on when I used the paperclip, but not the passenger side fan...

Here's a picture of my thermo housing...

[img=http://img13.imagevenue.com/loc498/th_62158_TempSensor1_122_498lo.jpg]

Can anyone ID the other two sensors? (The one on the left just has one Red wire)

Not sure why this could be, perhaps dirty/corroded connections? Or a bad Cooling fan Relay?

Due to the fact that it only comes on with a 25AMP fuse I'm not sure how to procede.

Any info / suggestions would be appreciated,

Thanks,

KS200

--edit--
Just went for a drive, 8mile or so in town and sure enough it started to overheat (with the 25AMP fuse). I stopped once when I was at normal temp and fan was not working and idle was ok... I stopped again once it got really hot and started to steam out of the reservoir overflow tank, the fan was still off and it was idling between 1200-2300 RPM. The fan didn't run until I turned the car off then it only ran for a couple minutes and shut off. No heat the entire way.

I then filled up the radiator and jumped on the highway, like before no problems with overheating and the heater worked... Drove it home for a mile or so and heater still worked and it idled fine. I parked it and let it run for a couple minutes then it started to idle bad again and I noticed some steam coming out of the reservoir so I shut if off (fan never came on).



--edit2--
Looks like I'm going to replace the coolant temp sensor and Relay... I also found in another thread that the top rad hose should be firm like a tennis ball, mine is very squishy so I'm also going to replace the Rad Cap...

If this isn't it I'll get a pressure test, might as well get the fan working first.

 

replace the thermostat

 

I didn't bother reading the big posts, but i did read a couple of the smaller ones. The purpose of the rad cap is to regulate the pressure. The cooling system needs to have a certain amount of pressure at all times so the coolant does not begin to boil inside the coolant system. When the coolant gets to hot (pressure to high) the cap will purge the coolant into the reservoir until the pressure becomes normal again. Check if the rad fan turns on. If the rad fan doesn't turn on and your temp is going up, then you have your possible prob. DON'T replace 15Amp fuses with 25AMP fuses. This is how you melt wires and start fires. Its 15Amps for a reason. Check if there is power to fan. If there is power at the fan but the fan does not turn on, chances are the motor has burned out. Also, check the voltage at the temp sensor if you suspect it is not good. THe voltage should go up as the temp goes up.

 

Thanks for the advice and info...

fglaustin:
I replaced the thermostat a couple days ago with no luck.

AgentofDarkness:
After reading your post about the AMPs I realized that I may have had too large of a paper clip, so I used a smaller one w/ the 15AMP fuse and the fan kicked on. I don't have a voltmeter, but will have access to one on Monday. I'll be running to the store shortly to get a new Rad cap...

Correct me if I'm wrong, but this is how I think the sensors are working:

1- Temp sensor (TW??) near the thermostat controls the fan after the car has been shut off.
2- Another temp sensor near the thermostat gives read-out inside the car.
3- Third temp sensor at the bottom of the radiator (CTS??) controls the fan when car is running.
4- Only One fan works for cooling engine, the other works only when the AC is on.
5- Relay - don't know...

Thanks,

KS200