Overheating, water circulating pump?

[supradh]

I have a 2001 Supra Legacy that has been giving me overheating problems. I originally thought the problem was the thermostat since I removed the t-stat (160F) and housing and verified that water was making its way up through the block and up to the thermostat housing. Replaced the t-stat and problem appeared to be solved the next weekend of running. However, problem re-occurred the following weekend (usually runs 175F, but jumped to 200F - steam out exhaust). Problem was somewhat intermittent.

Cranking the engine with the hose on the exit side of the raw water pump disconnected, I have verified that it is pumping a good supply of water. With the engine warm, I noticed that the intake hose to the circulating pump was fairly hot to the touch. I disconnected this hose from the t-stat housing and placed that end in a bucket of water. So, with the intake hose to the circulating pump placed in a bucket of water and cranking the engine - it did not suck any water out of the bucket.

Is this conclusive evidence that I have a bad circulating pump?

Is there any difference between an auto and marine circulating pump? Just wondering if I need to go to skidim.com or the local autoparts store.

Thanks!

[Blackntan90]

Not sure if that is the way to test the pump, but what do I know. You do want to get a marine pump though, as they are made with noble metals that will not corrode like automotive stuff will. and most have bi-directional impellers so if your engine spins to left it will still pump unlike the auto ones.

[Salty87]

circulating pumps normally weep water when they're bad.

are you sure the impeller is in good shape? water pressure from the hose can mask a bad impeller.

[jasun]

I was once tol by Vince at Skidim that a good test is if you take off the hose to the T stat from the water pump, it should fill a 5 gallon bucket in 15 sec @3000 RPM (if it is on the lake and not running a fake lake)

I had the same problem though that it was not sucking up water from a bucket. nothing leaking from the pump. Took the pump off and blew in one side and zero resistance. Changed the impeller and everything was good.

Not to hijack your thread, but my 86 Salt seems to run at operating temp of 125-135... this seems really low from what everyone is saying... is it? Could it be I have a 130 T stat?

[Salty87]

Not to hijack your thread, but my 86 Salt seems to run at operating temp of 125-135... this seems really low from what everyone is saying... is it? Could it be I have a 130 T stat?

anything is possible with a previous owner. harbor freight has cheap IR temp guns. they are handy to have on the boat or around the house.

[Moor]

@ JASUN - The 454 in my Sunsport runs about 130 degrees F also. I have checked it with an infered gun, the gauge is reading correct. I have never heard of a 130 t-stat, im not sure they make them in that low of a temp. Even after a hard run and a heat soak from sitting it never gets above 160, and cools right down when i fire it back up. To be honest i dont know what degree t-stat i have in mine, i never checked, but i'm not terribly concerned. Id much rather have it running cool than hot. As far as i know, it won't hurt anyting running on the cool side

[jaywidhalm]

Sounds like a bad impeller to me. Like Salty said, bad pumps will usually weep water. With a 160 degree t stat, from my experience, you should be running near or at the 160. Sounds like you are not moving enough water...usually due to an impeller issue. I would replace it and give it a shot.

[jaywidhalm]

@Jason and Moor: Is it possible that the t stat is stuck open and not restricting water to maintain a higher temp? You will not hurt anything running cool for sure, just may not get quite as much power as if running at the 160 mark. I do not think they make a 130 t stat.

[supradh]

I was once tol by Vince at Skidim that a good test is if you take off the hose to the T stat from the water pump, it should fill a 5 gallon bucket in 15 sec @3000 RPM (if it is on the lake and not running a fake lake)

I had the same problem though that it was not sucking up water from a bucket. nothing leaking from the pump. Took the pump off and blew in one side and zero resistance. Changed the impeller and everything was good.

Not to hijack your thread, but my 86 Salt seems to run at operating temp of 125-135... this seems really low from what everyone is saying... is it? Could it be I have a 130 T stat?

When you say you "replaced the impeller" - do you mean the impeller on the raw water pump? I have checked the raw water pump impeller (pulled it out and inspected - no damage to fins) and it appears to be in good shape. The output of the raw water pump seems to deliver a good deal of water while cranking with boat in the water, not fake a lake setup. I was referring to the circulating water pump at the front-top of the engine. The input hose to that pump was not sucking water from a bucket while cranking.

[TitanTn]

I agree that it's likely the impeller.

The 454s use a 140 degree thermostat. Sounds like you're right there. It could be a slightly flaky sending unit, but it sounds like you're good. Of course you can choose to run other temps, but the 140 is stock from what I understand.

[docdrs]

I disconnected this hose from the t-stat housing and placed that end in a bucket of water. So, with the intake hose to the circulating pump placed in a bucket of water and cranking the engine - it did not suck any water out of the bucket.

Is this conclusive evidence that I have a bad circulating pump?



Thanks!

No, it will not suck up any water unless the engine is hot and the thermostat open.

[docdrs]

If you removed the hose at the impeller it does not have to do much to suck water if the boat is sitting in the water. Remove it at the housing and see if it pushes water out there. Is your tranny cooler after your raw water pump? and is it clear? How old is your impeller? I have had a perfectly looking one not suck worth a crap.

[Moor]

I have a brand new impeller this year, the old one looked great, i keep it as a spare. tranny cooler is clear, raw water pump is moving plenty of water. Honestly i havent looked at the thermostat yet, i guess it could be stuck open, but i dont think so. the engine warms up too quick to have a stuck open t-stat (in my opinion).

[DAFF]

It could be a T stat which is sticking closed from time to time. This would cause a spike in the engine temp and create steam from the tail because of the hotter than usual bypass coolant. Once an impeller goes it is gone and the same for the water pump on the engine, the once and a while comes and goes condition as you have does not make sense. As for the water pump on the engine the tell tale sign they are gone is water out of the front of the pump through a small little hole where the shaft enters the pump.

Put a new T stat in the boat and pale test the raw water pump....

[docdrs]

I have a brand new impeller this year, the old one looked great, i keep it as a spare. tranny cooler is clear, raw water pump is moving plenty of water. Honestly i havent looked at the thermostat yet, i guess it could be stuck open, but i dont think so. the engine warms up too quick to have a stuck open t-stat (in my opinion).

confused .....who's thread is this?

[DAFF]

In the beginning did you replace the T stat with a new marine one, automotive replacement or put the old one back into the boat?? It could be the replacement T stat giving you the grief. I have seen many out of the box replacement parts go bad too.