Donzi1979

I'm trying to get my cooling system back to stock on my 99 HP500 and stable temps since i removed the procharger set up. I ran a cross over from Hardin for a couple years with a stat and bypass but couldn't get consistent temps and took too long to get oil temp up. So i put a GMB recalculation pump from Dennis Moore and added a Serria 18-1989 stainless t-stat housing thinking it was a cleaner install. Well now I can get water temps I wanted but over 3k rpm or 35mph my water pressure is 25psi and climbing. I don't think this set up should need a pressure relief valve like I had on the bypass set up.

This the way its set up now.
s Is the Gil exhaust too restrictive for this set up? Should I go back to factory set up with the the two hoses off the tee valve (spring and balls) to the risers? Hopeing the OSO brain trust has some ideas. Don't want to buy another $200 stat housing if that's not the issue.

Should I use one of these?

Mercruiser thermostat housing for 454 7.4 502 Chevrolet V8 1983-90

Donzi1979

Current set up

Griff

Most likely its the 2 hose T Stat with the internal bypass causing the jump.
With the 4 hose, the bypass could flow a lot more water to the risers. Now all that same water gets pushed through 2 hoses instead of 4.
I would just install a pressure relief valve.

My 502mpi's have the 2 hose and water psi is high @ 35psi at WOT. My 525SC with the same 4 hose set up as the HP500 barely hit 20psi

Donzi1979

Thanks Griff I ordered the one in the link and going with the the 4 hose set up. I didn't think this would be such an issue trying to get it dialed back in.

BUP

the check ball set up is there mainly for 2 reasons and water pressure controls it. if too much water pressure and opens up the check balls to far at low rpms - then too much water can be by pass and the risers runs too cold as condensation forms internally. The check balls provide persay warmer risers at low rpms so condensation does not from internally and or burns off on the tubulator dam portion that has formed then runs down on the dam.

I am not saying what you bought will not work - But throwing out the info on parts made here to keep an eye on quility.

If too much water by passes the engine will run hotter at any rpm level. Sometimes watch what you buy online as well. DM is huge into GLM parts as he use to work there - in the marine world GLM stands for GOOD LUCK MARINE. Many marine distributors drop all GLM products because of many reasons -- many dealers dropped GLM products because of those same reasons - I know cause I deal with 90 percent USA marine distributors for marine dealers. Not one major marine distributor carries GLM products. All will carry Sierra thou. Some of Sierra I am a fan of and some of their stuff I would never used. I would not use Sierra water circ pumps. They are not quaility made. Merc did about 4 years did but drop them as well.

right next door you could have bought USA made water circ pumps that are bi directional prob for the same money. All GLM products is CHINA 100 percent - I am not a fan of China parts nor the money going towards that end either.

Donzi1979

BUP I wish I had known it was all junk, and would have bought the Circ Pump from you if I had know you had them and still may need to. Now I'm not feeling too warm and fuzzy about the purchase I made yesterday for the t stat housing. Just trying to get this thing to work as it should with consistent temps.

BUP

the check balls and its spring tension is important as well. The end nuts can help with adjustments. Not saying it wont work. but again GLM is a main source for DM. Not sure where his water circ pump comes from either but might be GLM or Sierra or a good source --- do not know ??? With eyes on them, I surely can tell if its quality or not plus removing the backing plate can tell you alot..

The cage for seals and bearings is important and of course the casting finish of the pump itself. Sierra water circ pump is rough and cheap materials used. I will not use Sierra water circ pumps.

Merc years ago and Indmar had problems with GM water circ pumps - yes Indmar, Volvo, Merc and the rest all used GM water circ pumps. Merc change to source them thru Sierra - well that lasted about 3 or 4 years only.

The reason why GM pumps got dumped. Impeller cracked all the time. This is what we seen in the field very common hopefully pic in my next reply. Have to figure out to post pics.

BUP

Marine GM pump that all used for their OEM marine engines. NON LS versions. The problem was here in the pic. We seen many first hand. Merc then went to SIerra and that only lasted 3 or 4 years. Hence one of the reasons why I went out and searched for a quality pump to be made. Sometimes you get tired of the junk used on this stuff and the next junk that is offered to replace the first junk piece. Low cost most of the times is not the way to go for marine parts

AmiableDave

How does one know if condensation is forming internally? Would it show droplets externally?

BUP

rust on the exhaust valves. water droplets or rust on the spark plugs, pull risers off and look in the manifold exhaust portion for water and or rust especailly in the lowest portion of the manifold and or corners. Engine running with a miss ?

You have cat engines with a totally different set up and your exhaust is water jacketed way different with air gaps (space ) internally outside from the cats ( all internally ) then the water jackets are after the air gaps space. You also have persay dry joint exhaust.

The cats produce 600 to 800 degrees of heat when operating correctly. Overheating is way more important not to with these engines. Proper cooling a must. Have to go back to work soon. Messed around too much today.