M-EJ1

I'm replacing my thermostat today. It's one of the many steps I've performed in trying to diagnose an overheat problem that only happens at higher RPM's. This is on a 91 integra, stock motor, BTW. I've replaced the radiator, upper hose, thermostat, rad. cap, and the car has a recent water pump + timing belt. (last 10k miles)

I noticed that my lower hose is somewhat flexible and easy to pinch shut. Should it be that flexible, and should it have a spring in it (mine doesn't)? The reason I ask this is that I've heard on other makes of cars (namely, Jeep 4.0L) that when replacing the hoses, one should always use one that has a spring in it (OEM) instead of a parts store replacement (no spring), because at high RPM's, the water pump can suck the lower hose shut, cutting off the coolant to the block.

Does this sound reasonable? Do the OEM hoses come with a wire spring inside them? I haven't found any information on here about this (tried a search). I don't have any Acura dealers around here I can call up, but if nobody knows the answer I will make the long distance call to one in Lynnwood and see what their parts guy says.

Anybody got any ideas on this? Also, how about the overheat problem... if it isn't supposed to have a spring, what's causing my high RPM overheats? I can idle all day, drive on the highway all day, but as soon as I push it hard above say 4.5k, the temp gauge just skyrockets... if I keep the car moving and go easy on it, the temp gauge drops just about as fast as it climbs when it gets too hot.

M-EJ1

Bump... nobody has ever replaced a lower rad. hose on a DA?

Lord Helmet

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by M-EJ1 &raquo;</TD></TR><TR><TD CLASS="quote">Bump... nobody has ever replaced a lower rad. hose on a DA? </TD></TR></TABLE>

oem lower radiator hose don't have a metal spring in them. My old DA never had a metal spring when I bought it from the honda stealership. For the heating up only at higher rpm. What have you done to the car so far?

M-EJ1

I've replaced just about every piece of the cooling system...

It has... brand new radiator from performance radiators, new OEM radiator cap, new OEM thermostat, new upper hose, new coolant (bled and topped off properly, no air bubbles), tested the ECT sensor and got almost exactly 300ohms at operating temp, tested the fan... it comes on when voltage is supplied to it, and it comes on when I let the car idle for an extended period. I have receipts for a new timing belt and water pump a little over 10k miles ago, which the previous owner had done.

The car drives awesome and runs great, except for this problem. What happens is this... at first, when the car is cold, I can start it and drive it no problem. The temp gauge NEVER gets above about 1/3, I can let it sit and idle in the driveway for 20 minutes and it doesn't overheat, the fan comes on, everything seems to work proper. I can drive it on the highway no problems, temp gauge stays put.

The problem comes after I take it up close to redline once in a drive. I'll floor it from a stoplight and rip through the gears, and as I get to about 45-50mph, I notice the temp gauge is almost all the way to the right, so I quickly let up on the gas and shift up a gear, and the temp starts dropping as I let off the gas and shift and pick up some speed. After this happens once during a drive, it will do it at every stop light or stop sign for a while, then it will quit doing it until I take it up close to redline again.

Also, BTW, it doesn't do this every time I rev it high, so I figure something intermittent is happening, and I'm almost SURE that it's the lower radiator hose... it acts exactly like what I would imagine happening when the lower hose is sucked closed... soon as I let off the gas and shift, the temp starts dropping... and I mean, it drops FAST. way faster than it should if things were really that hot.

Lord Helmet

My question is the engine stock? car stock? what's the mileage on the engine? what mods have you done to it? You're not answering my first question.

You're hiding something.





Modified by sleeperciv at 8:43 PM 3/21/2005

M-EJ1

Hiding something? I'm trying to diagnose a problem here... what would hiding something do for me?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by M-EJ1 &raquo;</TD></TR><TR><TD CLASS="quote">This is on a 91 integra, stock motor, BTW.</TD></TR></TABLE>

Stock motor, 250k on the chassis, mileage unknown on motor (it's a replacement from another '91). Motor has good compression (175, 170, 175, 175) and burns a very small amount of oil.

The car has an intake and exhaust, that's it.

Lord Helmet

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by M-EJ1 &raquo;</TD></TR><TR><TD CLASS="quote">Hiding something? I'm trying to diagnose a problem here... what would hiding something do for me?

Stock motor, 250k on the chassis, mileage unknown on motor (it's a replacement from another '91). Motor has good compression (175, 170, 175, 175) and burns a very small amount of oil.

The car has an intake and exhaust, that's it. </TD></TR></TABLE>


It can't be the lower rad hose because the water pump is on the side of the engine and the hose is in front the engine. Also you ever power flushed the cooling system before?

M-EJ1

When I replaced the radiator, I drained as much coolant out as I could, removed the upper hose, lower hose and thermostat and ran garden hose pressure water both ways through the block.

Lord Helmet

well there's only two other things I can think of that could cause that amount of heat at that high of a rpm and that would be a small leak in the head gasket or too lean of a a/f mixture at the higher rpm which would raise the combustion chamber tempertures. Dirty injectors would cause a lean mixture, clogged fuel filter too, camshaft timing also.

00s2KkId

could it be a small head gasket leak? like when at WOT air might leak into the coolant passages and cause bubbles in the coolant system??? not sure but thought it might help

edit: should of read sleeperciv post

M-EJ1

Well... I've been trying to avoid coming to the head gasket conclusion... (replacing all the other stuff first... ), but I've known in the back of my mind that maybe that's what it is.

I just cleaned the injectors a week or two ago, trying to diagnose a different problem I was having that is fixed now. The car ran odd... misfired, idle sucked, etc... valve lash was too tight... guess the previous owner thought a valve adjustment meant screwing them all the way down so there was hardly any play.

I've also replaced the fuel filter as well trying to diagnose the old problem. The ignition timing is right on about 17 degrees, and I run 92 octane in it so I should be fine there. The cam timing, however, I am not completely sure of. When I did the valve adjustment the other day, I couldn't get both arrows on the cam gears to point perfectly straight up. They were both angled in a tad. Is that normal? I took some pictures, but I don't have the camera with me right now to pull them off. I'll have to post them up later on.

Would one or the other cams being off a tooth on the t-belt cause this type of problem, despite the fact that the car still runs great other than this issue?

00s2KkId

the cam gears wont point straight up...they will be off a little bit...but when those arrows are up there is another set of arrows that point directly at each other where the cam gears meet...make sure those are perfect

M-EJ1

I'll have to double-check tonight on the other marks... I don't remember seeing any other marks on the cam gears when I did the last valve adjustment, but I'm not sure. Anyway, I don't think either of the cams is off because from my understanding it would not run very well at all with either off by a tooth, and this motor runs perfectly except for the heat issue.

I'm probably going to get another opinion from a mechanic locally here before I start tearing the top of the motor apart to put a new head gasket in... I guess it could be a very SMALL leak that is letting compression into the coolant and maybe only at high RPM's is there enough pressure to open it up... but I've always been told that the car would run shitty even if it was just a small leak, because coolant would leak into the cylinders and compression would leak out.

Anyway, if anyone has any other ideas about why it would be overheating so much and so quickly once I take it up there in the RPM's, then cool down so quickly as well, post up and let me know. I'm all out of ideas. I replaced the lower hose last night anyway just for good measure and took the car out on the highway and romped on it and it started overheating again, as always.

BTW... if I replace the headgasket, what would a good choice be for an aftermarket one? Cometic? I'm thinking about boost for this motor later on, but I don't really want to put a thick gasket on now and hurt performance. Ideas?

M-EJ1

Bump... still trying to figure this out...

Anybody else ever have their car do this? What was the problem?

I guess I'm going to order a Cometic gasket and some ARP head studs when I get paid on the 1st, but I'm just contemplating the problem. It actually hasn't overheated in a couple days, and I've been flogging on it. Seems to just happen once and then disappear for a while. I'll think it's fixed and take it up to the redline and the temp gauge will suddenly start climbing.

00s2KkId

when you "flogged" it, did u take it to redline?

M-EJ1

Yes, but the problem is still there. It's done it twice to me since I last posted (I just can't keep my foot out of it sometimes).

Anyway, it's intermittent is what I'm trying to get at, it does it sometimes and won't do it other times. Seems more likely to do it when I'm on the highway where I would speed up for a longer period of time (taking it through the gears and holding speed) rather than ripping through the gears from a stoplight until 35 then just cruising. I don't know, it's hard to describe. It overheats when I take it to redline, but only SOMETIMES. I could drive it for a week and take it up to the redline through the gears fairly frequently, and it would hold temp just fine, then one time when I take it to redline it will overheat violently, as if the coolant just suddenly stopped flowing. If I baby it and let the revs drop off and just drive it normally, the temp just drops back down to normal after a few hundred feet. If I keep on it, it will boil over.

The thing that's puzzling to me, and what lead me to think about the lower hose being sucked closed by the water pump, was that when the temp gauge is rising (and it rises VERY fast), I can take my foot out of the throttle and it will start dropping almost immediately as long as I drive it like a granny for 30 seconds or so... the temp gauge will skyrocket, then just drop like a rock