PDA

View Full Version : okay, cooling issue has me CONFUSED!!!!


DooSPX
10-24-2009, 05:02 PM
I have been chasing a cooling issue from my 91 PS190 for a little while now (she has NEVER had a problem since she was new in 91 but she hates me now for letting her sit for a long time :()
She runs perfect with no T-Stat in, 140-150 all day.

things I have done:

I have pulled the intake line and tranny cooler looking for blockage (ZIP!!)
replaced impeller in RWP
replaced RWP
replaced T-Stat (tried 2 different stats, one new one from a working Indmar 351)
pulled all the cooling system lines looking for blockages or air leaks
checked the manifolds for blockages
checked my inline valve thats before the tranny cooler for air/water leaks (replaced with straight pipe and tested on the lake
replaced circulating pump
Same darn thing. Now for the kicker, for the heck of it, with the T-Stat in I turned my inline valve only slightly open so some of the water from the hose would run out the intake on the bottom and the rest would go to the RWP... the temp went DOWN!!!! :confused::rolleyes:

anyone ever seen this? it seems like there is to much cool water flowing over the T-Stat preventing it from opening maybe?

btw, the new t-stat does open, I tested it in hot water. the other stat from a working indmar. Yes, both were the correct 142...

DooSPX
10-24-2009, 10:13 PM
anyone have any idea's?

WilliM1940
10-24-2009, 10:35 PM
1. Maybe your gauge or sending unit are bad

2. How long does it take to suck a 5 gallon bucket dry, and is plenty of water exiting the exhaust?

Just things to consider.

DooSPX
10-24-2009, 11:14 PM
There is plenty of water coming from the exhuast, the gauge and sending unit are fine. With out a T-stat, it runs just like it should. There is so much water coming from the RWP that its like a hose on full blast.
Both T-stats are good.
if I cut the flow from the hose just a little bit, the temp will actually go down.... :confused::confused:

thatsmrmastercraft
10-25-2009, 02:59 AM
Your boat must have gremlins.

On a serious note, how hot is hot when running with the thermostat in? So far it doesn't make much sense.

JLeuck64
10-25-2009, 08:24 PM
If there is air around the t-stat, or the sending unit for that mater, neither will operate they way should. Both items need to be submersed to function properly.

You say the boat had sat for a period of time... Any chance you guys experienced some freezing weather during that lay up? If so, you may be chasing a cracked exhaust manifold or a cracked head or a cracked block. When combustion gases get pushed into the cooling system it can cause overheating issues. With the t-stat in it traps those gases making the condition seem worse. With the t-stat out the symptoms seem to disappear but the cause is still present.

Heck it could be as simple as a bad gasket between the exhaust manifold and the collector... if you can see rust stains working their way down the outside of the manifold it's time for some new gaskets.

DooSPX
10-26-2009, 10:46 AM
changed the gaskets on the risers....

temp with the t-stat in is 190+ BUT i shut her down when i hear the buzzer. with out the stat, its 140-150

I live in south central FL, the boat sleeps in a insulated garage. no freezing temps....
how can i tell if the block or head is cracked with out pulling the motor? I have been checking the oil everytime i do something on it just looking for signs of water....

thatsmrmastercraft
10-26-2009, 12:27 PM
Your experience sure points to a bad thermostat. At the risk of being redundant, I would buy a new thermostat and give it a try. Over the years I have had the occasional problem with a sluggish thermostat - even one or two defective from new. They are made too cheap and I would be happy to pay $25 for one if you could find a good one that will last.

Either that, or get the boat exorcised.

DooSPX
10-26-2009, 12:45 PM
thanks, i keep thinking that too, but i tried a thermostat from a friends indmar ford 351 same 142 stat, and it did the same thing. he had the boat out a few days prior to that on the lake all day.

also, anyone know a good priest, just in case? :) :)

shunra
10-26-2009, 12:51 PM
What would happen if you have been installing the thermostat upside down? Just a thought. Any chance of that?

DooSPX
10-26-2009, 12:54 PM
thanks for the thought, but the thermostat is installed correctly. it also doesnt sit right if you flip it around.

Laurel_Lake_Skier
10-26-2009, 10:19 PM
Have there been any changes to the engine? I'm thinking about the possibility of an intake or head gasket being installed so that cooling passages are blocked......without the thermostat, you should be well under the 150 you mention so I don't think things are cooling as they should be.

DooSPX
10-26-2009, 11:06 PM
no, no changes to the engine. I am planing on heads and an intake but only when I tore down the more. but never planned on it quite this soon.
I would guess that something could be blocking a coolant passage, maybe a piece of rust or something.

Sodar
10-26-2009, 11:18 PM
Running without a T-stat actually has the possibility of making the motor run warmer than usual and the same goes with the reducing the flow on the hose. I am no chemist or engineer, but it has something to do with water rushing through the passages as opposed to slowing a bit and having more of a chance to pull the heat from the block.

Second, what indications do you have that the engine is running hot? Is it just the gauge rising or is it getting noticeably hot?

Lastly, have you tried back flushing the engine? Maybe even thought water is flowing, there is a blockage?

JLeuck64
10-26-2009, 11:33 PM
Someone answer this question for me... Did MC's from this era have electronic ignition or were point distributors still OEM? The reason I ask is if the advance weight springs break it causes to much ignition advance which can cause overheating too.

thatsmrmastercraft
10-27-2009, 01:02 AM
Good thought on the dist. advance stuck, but the fact that it runs sufficiently cool without the stat in negates that as a possibility.

The problem almost has to lie with the engine running OK without the stat in place and too hot with the stat in place. There was an earlier suggestion about the stat being installed in the proper orientation. That could be a problem as it should disrupt the flow. I suspect that somewhere the obvious problem is being overlooked - only because I have been there enough to has caught myself after pulling my hair out. Like all the time I spent chasing how the water was getting into my oil, when I was doing it to myself by turning the hose on my fake-a-lake prior to starting the engine.

Sometimes as obvious as the nose on your face isn't obvious enough.

88 PS190
10-27-2009, 01:26 AM
The thing that really doesn't fit is the closing the valve causing it to run cooler.

Have you always had this valve? Or did you install it more recently?

Have you tested on the lake with the system sucking water like its meant to? Or only on a hose?

DooSPX
10-27-2009, 10:17 AM
the valve has been there for a very long time. but i tried removing the valve and saame thing.
it heats up on the hose and the lake.

TRBenj
10-27-2009, 11:00 AM
it heats up on the hose and the lake.
On the lake WHEN? At idle? Or at speed?

If it overheats at idle but cools at speed, youre sucking air somewhere between the hull fitting and RWP. Go over all hose clamps with a socket (NOT a screwdriver). Make sure you dont have cracked hoses. If youve got something else in line like a strainer, valve, etc, make sure its sealing properly- or remove it for troubleshooting.

If it overheats at speed, youve either got a blocked passage or a RWP (or impeller) problem. If the RWP is drawing air past its seal, this will cause you to overheat and you need to rebuild the pump.

190 is way too hot for a 142 stat, and 140-150 is way too hot with the stat removed. Something is wrong for sure.

Bruce Carr
10-27-2009, 11:39 AM
Check for vacuum leaks all the way from the thru -hull fitting to the RWP. Make sure your transmission intercooler isn't cracked or the intercooler drain plug leaking allowing air to be sucked into the cooling line. The RWP seals could be worn also allowing air to be sucked into the cooling line. I had a similar issue and found that I had not tightened the trans intercooler drain plug.

Hollywood
10-27-2009, 01:54 PM
Why don't you please start over and simply describe your problem, not the tail chasing you have done.

DooSPX
10-27-2009, 03:04 PM
On the lake WHEN? At idle? Or at speed?

If it overheats at idle but cools at speed, youre sucking air somewhere between the hull fitting and RWP. Go over all hose clamps with a socket (NOT a screwdriver). Make sure you dont have cracked hoses. If youve got something else in line like a strainer, valve, etc, make sure its sealing properly- or remove it for troubleshooting.

If it overheats at speed, youve either got a blocked passage or a RWP (or impeller) problem. If the RWP is drawing air past its seal, this will cause you to overheat and you need to rebuild the pump.

190 is way too hot for a 142 stat, and 140-150 is way too hot with the stat removed. Something is wrong for sure.


it overheats at idle and at speed.
I have check for blocked passages on the easy to get to parts, but not the motor )i.e. heads or block)
the RWP is brand new, so is the circ. pump, etc.

DooSPX
10-27-2009, 03:11 PM
it all started from a overheating issue at idle, but would cool down at speed. I pulled the t-stat and tested it. It was stuck. ordered new t-stat, then it overheated at idle and speed, RWP had a new impeller, so i got a new RWP. same thing. checked all the lines again, pulled exhaust manifold risers and replaced gaskets, same thing.
borrowed a friends thermostat that works from his indmar ford, same thing.

JLeuck64
10-27-2009, 04:47 PM
Well... sounds like you have covered all the basics you can from the outside looking in.

Can you find somebody to perform a cylinder leak down test for you locally? In the auto world I use this test to tell about the integrity of the combustion chamber seal. Valves, Rings and even the headgasket can be checked using this procedure. Of course, with a fresh water cooling system it will be a little tougher to determine if there is a leak than it would with a closed cooling system. But, if you have an abnormally high percent of leakage in say 1 or 2 cylinders it would give you good reason to start looking inside the engine for more clues...

DooSPX
10-27-2009, 09:58 PM
I am going to do that next. im going to perform a leak down test. I am out of options on this.

dodgybee
10-28-2009, 07:50 AM
i had a problem that my raw water filter housing was not sealing properly and was causing a pressure loss in system allowed air in and cooling was very erratic sometimes overheating badly.
Renewed housing seals bingo when in water keeps filter housing full no air and no overheating.
Hope this helps.

TRBenj
10-28-2009, 11:18 AM
it all started from a overheating issue at idle, but would cool down at speed.
Like I said, this would imply that youre drawing air in between the hull pick up and RWP. Are you sure that every single piece in between (strainer, valve, etc) doesnt have a crack in it? Are you sure every single hose is in good condition (no split ends, etc) and that every hose clamp is tight (with a socket, not a screwdriver)?

Im assuming that when you say "it would cool down at speed" that it would run a steady 160 as it should if you kept the boat on plane for a min or so. If thats not the case then you need to describe the problem better.

I pulled the t-stat and tested it. It was stuck. ordered new t-stat, then it overheated at idle and speed, RWP had a new impeller, so i got a new RWP. same thing. checked all the lines again, pulled exhaust manifold risers and replaced gaskets, same thing.
borrowed a friends thermostat that works from his indmar ford, same thing.
Was the stat stuck open or closed? If it was previously regulating temp (even if only at speed) I find this very peculiar. I doubt the stat has anything to do with your problem.

Hows the condition of the impeller in the new RWP? Have you checked it? If the new pump is leaking air, that would cause the same symptoms youre seeing. If its not cooling at speed anymore, then something you did caused the change- so retrace your steps and double check everything. Dont continue to throw parts at the problem!

DooSPX
10-28-2009, 01:42 PM
the original thermostat was stuck closed.
what is strange is that it will run fine with no thermostat in. without the stat it hasnt even got to 160, normally 140-150 tops.
i have checked all the lines and fittings more times than I want to count (with a socket). I have also checked the thru hull pickup as well.
yes, I did pull the impeller in the new RWP to check it, it was good.

JLeuck64
10-28-2009, 04:31 PM
Agreed, with the original t-stat stuck closed it may have caused some internal damage to the heads/head gaskets. Next logical step in my mind would be to check compression and perform a cylinder leakage test. The results should give you more direction. In addition take a good look at the spark plugs as they come out. A lot of times if you have a mechanical problem within that cylinder it will show symptoms on the plug. In your case if there is water entering the combustion chamber it would cause that spark plug to look cleaner than the others.

TRBenj
10-28-2009, 06:00 PM
the original thermostat was stuck closed.
what is strange is that it will run fine with no thermostat in. without the stat it hasnt even got to 160, normally 140-150 tops.
i have checked all the lines and fittings more times than I want to count (with a socket). I have also checked the thru hull pickup as well.
yes, I did pull the impeller in the new RWP to check it, it was good.
140-150 without a stat is way hot. It shouldnt get much above 100deg without one- so thats just another sign you have a cooling issue.

When you put the rwp back together, did you notice if it has the oring installed properly? What about the gasket between the halves? My guess is that its drawing air.

Laurel_Lake_Skier
10-28-2009, 06:07 PM
what is strange is that it will run fine with no thermostat in. without the stat it hasnt even got to 160, normally 140-150 tops.
Without the thermostat, this is not running fine.....you should not be seeing temps get that high without the thermostat in place. I would think that without the thermostat in place, you would hardly see the gauge move under normal conditions. Without the thermostat (or some other obstruction) that raw water pump should be pushing a lot of cold water straight through the engine - not giving it time to warm up at all. Something is obstructing the flow of water to the engine or within the engine.

DooSPX
10-28-2009, 10:28 PM
im going to do a leak down test this weekend I think. I have to get to the bottom of this.

TRBenj
10-29-2009, 12:06 PM
A leak down test is all well and good and may indicate if you have a major engine problem, but its not likely to help with the cooling issue. If you are determined to go down this path, I suggest you do a compression test first- if everything comes up ok there, dont bother with the leak down.

Id be looking closer at potential blockages in the cooling system and at the RWP instead.

DooSPX
10-29-2009, 12:39 PM
the new RWP came as a complete unit. I did check the impeller on it though. I just unbolted the old one from the crank pulley and bolted in the new one.

shunra
10-29-2009, 02:42 PM
Without the thermostat, this is not running fine.....you should not be seeing temps get that high without the thermostat in place.

OK you have a high temperature with or without the themostat in place. This definately could be a blockage but couldn't it also be the sending unit.

I know you previously stated that the sending unit was fine, but it sounded like that assumption was based on the temperatures you were seeing without a thermostat in place. If those temperatures are also high it seems like the sending unit could at least be suspect.

It might be worth a check before you start tearing things apart.

blackcreek
10-30-2009, 11:00 PM
There are two water pumps in the system, the raw water pump delivers it to the engine and manifolds, excess goes out the exhaust. The water pump on the engine circulates the water through the block, are you sure your engine water pump is good?

DooSPX
04-17-2011, 11:08 PM
macattack recommended that I update this thread. I forgot all about it.

here is what I did to fix the issue.... talking with a Ford Small Block specialist, this is a pretty common thing on older SBF's.

Well, I did get it figured it out and now it runs PERFECT. I will tell you what I did in steps...
Checked Trans Cooler and valve (custom valve for starting on land), replaced impeller, nothing. Replaced thermostat, nothing. checked all water hoses for blockages and did the same in the exhaust risers, nothing. replaced circ. pump, still nothing. Turned out on the fords, there is a water passage on the block and heads that is large, well the head gaskets have a opening for the passage that is half the size. That passage on the gaskets had blown out and made the passage full size. I never knew this about fords, but a friend is a ford specialist, and has built many bad fords. He told be about it after after I called him looking for a suggestion and telling him everything I already did. He knew as soon as I told him the issue and its common on ford small blocks.
So I replaced the head gaskets and all is good as new. I do not regret replacing my circulating water pump though, at least now I have peace of mind about my cooling system.

I hope this helps.