Here's an update on my problem child;

The fan is kicking in - new temp switch.

I tried flushing the rad with Prestone Heavy Duty cleaner. I figured it had to be caustic enough to do something since it had a "neutralizer" with it. Wrong! No effect! A coworker came up to me and said that he had "one of these rotting in [his] back yard" and did I need any parts? I asked about the radiator not expecting it to be in terribly good shape. He said it had a blown head gasket. Went to check it out. Sure enough, oil in the water - preservative! Cleaned it up, put it in, worked great right up until I burned a valve - on the way home from putting in the rad! Now I get to scour the bone yards for 81 Prelude 1.8L parts. Fortunately the Accord had the same engine, so it shouldn't be too difficult to find stuff.

By bruce (67.200.12.219) on Saturday, May 08, 2004 - 04:29 pm:

just my 2 cents, make sure the fan is kicking in....we all know how good that thermo switch is...(how many of have it hotwired?) check the thermstat, if it is not overheating at idle, but overheats driving it, your radiator is probably toast. I just went thru these same symptoms on my daughters chevy. fine at idle all day long, driving it .....15 miles and it overheated.

By Glenn Mauk (Gmauk) (64.166.166.209) on Saturday, May 08, 2004 - 01:10 pm:

The thermostat was the first thing I changed (cheap & easy). It overheats at speed but not at idle. I email'd Colin and he wrote that his 76 cvcc with modified 2.0 Prelude engine cools fine with the stock rad. The radiator does look pretty built up. The guy I bought the car from has a line on a new one; probably the last one on the West coast.

By RP Singh (24.187.121.100) on Saturday, May 08, 2004 - 07:39 am:

I agree with Dave - check the thermostat. I overheated and seized the engine on my 80 Civic within one day of buying the car. That was in 96. Let the engine cool off, replaced the thermostat, flushed and replaced coolant and it was ok. lol

Eight years and 80k miles later she still runs absolutely fine. Honda engineers must have planned for morons like me!

Read the book - the coolant should start circulating once the engine reaches operating temperature and the thermostat opens. Check other things - does the fan run after the engine reaches operating temperature. Possible culprits are bad thermostat, bad thermoswitch, bad fan, low coolant level, air trapped in coolant, blocked radiator, coolant leak. Most of these are very easy to check. Your book would be the best source.

In case you need a thermostat - I have a new one for an 80 civic. Don't know if that would fit. In case you need it and it fits then you can have it cheap!

By Dave (209.226.248.77) on Saturday, May 08, 2004 - 07:11 am:

It could be as simple as a sticking thermostat. Let it run with the cap off and see if there is circulation in the rad as the stat opens. Does it do this when your driving it easy or when you are putting your foot into it? Does the rad look to have a lot of build up in it? I have seen some rads that were so plugged that it was probably flowing only %10 of what it should have been flowing. If it looks like it is gunked up then try flushing it. There are quite a few products on the market for that. Keep us posted

By Jonathan (68.193.10.141) on Friday, May 07, 2004 - 11:40 pm:

I'd replace the radiator and see where you go from there. It's next to impossible to diagnose a cooling problem accurately with bad parts in the mix. Shea's friend Colin has one for sale in his other post, and they pop up on e-bay every once in a while.

By Shea Laking (Sheaman71) (66.185.85.79) on Friday, May 07, 2004 - 10:09 pm:

Glenn,

I'm guessing your car is a CVCC (since you said it had a 1500 in it originally). My buddy Colin has a '76 CVCC with a newer Prelude engine in it...not really sure what's been done to it in regards to the cooling system. With some luck he'll see this and post a reply. His handle here is "CVCCx2." Hope you can get it fixed up without too much trouble.

Regards,
Shea

By Chaffneue (Chaffneue) (64.180.112.150) on Friday, May 07, 2004 - 08:16 pm:

You might want to ask a rad shop.. they'd probably know more about how to modify the mounts and whatnot.. I've heard using a 3 core CVCC radiator matrix and tanks in the 2 core 1200 mounts works with little fuss, you'd probably want to get better shoruding for the fan than the standard 1200 fan. but I don't know if the swap is enough cooling for a modern 1800 engine.

-Richard

By Glenn Mauk (Gmauk) (64.166.166.209) on Friday, May 07, 2004 - 06:01 pm:

Help! I just bought a 78 Civic that someone changed out the 1500 for an 81 Prelude 1800. It goes about 30 minutes and overheats. I do know that the radiator is bad. I know where a new one is (for the stock engine). But does anyone know a larger radiator that will fit woth the least amount of modification? Does it even need a larger radiator?